Multidimensional Engineering of Nanoconfined Catalysis: Frontiers in Carbon-Based Energy Conversion and Utilization

Abstract

Amid global efforts toward carbon neutrality, nanoconfined catalysis has emerged as a transformative strategy to address energy transition challenges through precise regulation of catalytic microenvironments. This review systematically examines recent advancements in nanoconfined catalytic systems for carbon-based energy conversion (CO₂, CH₄, etc.), highlighting their unique capability to modulate electronic structures and reaction pathways via quantum confinement and interfacial effects. By categorizing their architectures into dimension-oriented frameworks (1D nanotube channels, 2D layered interfaces, 3D core-shell structures, and heterointerfaces), we reveal how geometric constraints synergize with mass/electron transfer dynamics to enhance selectivity and stability. Critical optimization strategies—including heteroatom doping to optimize active site coordination, defect engineering to lower energy barriers, and surface modification to tailor local microenvironments—are analyzed to elucidate their roles in stabilizing metastable intermediates and suppressing catalyst deactivation. We further emphasize the integration of machine learning, in situ characterization, and modular design as essential pathways to establish structure–activity correlations and accelerate industrial implementation. This work provides a multidimensional perspective bridging fundamental mechanisms with practical applications to advance carbon-neutral energy systems.

1. Introduction

In the contemporary era, there is an indisputable and increasing prevalence of energy consumption and environmental pollution. These phenomena pose a significant challenge to the global energy structure and the preservation of the environment [1,2,3]. The warming effect of carbon dioxide (CO₂) and methane (CH₄) has been demonstrated to enhance the greenhouse effect by absorbing longwave radiation. This has been shown to significantly increase the frequency and intensity of extreme weather events, such as heatwaves and torrential rains. Furthermore, the release of methane from thawing permafrost in the Arctic region has been shown to create a positive feedback loop that accelerates climate warming [4]. Carbon monoxide (CO), a colorless and odorless gas, primarily originates from incomplete fuel combustion in sources such as vehicular exhaust and gas-powered appliances. Upon inhalation, it binds to hemoglobin, impeding oxygen transport and potentially resulting in headaches, unconsciousness, or even fatal outcomes. Additionally, CO is involved in photochemical reactions that generate ozone pollution and exacerbate the greenhouse effect [5,6]. Given the aforementioned circumstances, the proposal of the dual-carbon strategy (carbon peaking and carbon neutrality goals) has gained critical importance [7,8,9]. This approach has been shown to substantially impact greenhouse gas emissions, which are a significant contributing factor to global warming and climate change (e.g., glacial retreat and sea-level rise). Furthermore, it has been demonstrated that this approach can drive the energy transition by shifting from conventional fossil fuels to clean alternatives such as solar and wind power, thereby enhancing energy security. Consequently, developing efficient and low-pollution energy conversion technologies has emerged as a prominent research priority. Particular emphasis is being placed on catalytic conversion technologies for carbon-based energy systems.

Research on the catalytic conversion of carbon-based energy encompasses not only traditional thermal catalysis [10,11,12,13,14,15,16] but also emerging technologies such as photocatalysis [17,18,19,20,21,22,23,24], electrocatalysis [25,26,27,28,29], photothermal catalysis [30,31,32] and photo electrocatalysis [33,34]. These technologies offer critical pathways toward sustainable development and carbon neutrality goals by optimizing catalytic processes, enhancing energy conversion efficiency, and reducing pollutant emissions. Jeffry et al. investigated utilization technologies for greenhouse gases (e.g., CO₂ and CH₄), including electrochemical reduction, advanced catalyst systems, photocatalytic reduction, and plasma techniques [35]. Cai et al. modulated the interfacial properties of Cu surfaces using ionic liquids, altering CO₂ electroreduction pathways and providing insights for optimizing product selectivity [36]. Yang et al. synthesized PtNPs@Th catalysts via organic doping, achieving stable CO₂ electroreduction to CH₄ under acidic conditions for over 100 h, thereby advancing dual-carbon strategy-compatible technologies [37]. Yu et al. demonstrated transition metal-doped ZnO as a photocatalyst for reducing carbon dioxide to methane, with an output of 1539.1 µmol g⁻¹ h⁻¹ and a selectivity of 90%. The integration of this photocatalyst with genetically engineered bacteria to synthesize valuable products, such as sucrose, established a sustainable carbon recycling route [38]. Hu et al. developed Co–In dual single-atom catalysts supported on C₃N₄ for CO₂ reduction, achieving a CH₄ production rate of 18.8 μmol g⁻¹ h⁻¹ with markedly enhanced selectivity compared to single-atom systems [39]. Zou et al. synthesized TiO₂-supported Ni–Ru bimetallic catalysts with alloy and non-alloy structures for hydrogenation, revealing that the Ni–Ru system acts as an “H-atom valve” by regulating H₂ spillover, enabling complete switching of CO₂ hydrogenation selectivity [40]. These technologies are pivotal in achieving sustainable development and carbon neutrality goals by optimizing catalytic processes, enhancing energy conversion efficiency, and reducing pollutant emissions.

There have been substantial advancements in catalytic conversion technologies for carbon-based energy systems in recent years. These advancements can be attributed to interdisciplinary collaboration and integration, which have played a pivotal role in the emergence of novel conceptual frameworks within this domain. The concept of nanoconfined catalysis, pioneered by Xinhe Bao, refers to a catalytic mechanism that modulates catalyst electronic structures via nanoscale spatial or interfacial confinement effects, enabling precise control over reaction pathways and product selectivity [41]. Its core principle is leveraging quantum effects and microenvironment synergies to stabilize active sites and optimize intermediate adsorption energy, thereby markedly enhancing catalytic efficiency and selectivity [42,43,44,45,46,47,48,49]. Extensive research on nanoconfined catalysis has been conducted, with Web of Science data indicating a steady increase in publications concerning the development of nanoconfined catalysts for converting CO₂ and CH₄ into high-value chemicals (Figure 1a). For instance, Fan et al. achieved efficient room-temperature methane conversion to liquid C1 oxygenates by confining Cu atoms within ultrathin Ru nanosheets, with detailed reaction mechanisms elucidated [50]. He et al. developed thermally stable sub-2 nm Ni nanoparticles confined in SBA-15 mesochannels through combined surface hydroxyl modification and pore confinement strategies, addressing Ni catalyst deactivation via sintering and insufficient active site exposure in dry methane reforming [51]. Mo et al. confined the Ru₃–SCs in Ni–PCN (porous carbon nitride)-222-PyrA by using the pre-coordination confinement strategy, and the resulting complex can efficiently electrocatalyze the reduction of CO₂ to CH₄ [52]. Lv et al. revealed that Cu–MOR catalysts synthesized via ion exchange contain elevated levels of zeolite-confined Cu²⁺ species, which synergize with non-thermal plasma to enhance direct methane oxidation to methanol [53]. Lu et al. designed Ag@Cu₂O cascade nanoreactors with tunable shell thickness for CO₂ reduction, demonstrating that moderate shell thickness optimizes CO diffusion and confinement effects to boost C₂ product selectivity [54].

The literal interpretation of “confinement” typically evokes images of active catalytic components spatially confined within defined boundaries or reactant molecules isolated in specific microenvironments. Previously, Jiao et al. summarized the achievements of Professor Xinhe Bao’s research group in the field of nanoconfined catalysis and divided the framework of nanoconfined catalysis into four parts: 0D, 1D, 2D, and interface [41]. However, numerous studies on confined catalysis, although not explicitly framed in terms of “nanoconfined catalysis”, inherently fall under this category. To better illustrate the outstanding contributions of researchers worldwide in this field, we further categorized these systems into four classes based on dimensional classification: 1D, 2D, 3D, and interfacial nanoconfined catalysis. Yang’s team employed a Random Forest model combined with Grand Canonical Monte Carlo simulations, revealing that in carbon nanotube (CNT)-confined catalysis, shortened catalyst bond lengths lead to weakened binding energy and a downshift of the d-band center, elucidating the mechanism behind activity enhancement or suppression [55]. Fan’s team designed a C/Cu/C sandwich-structured catalyst using a bidirectional freezing and freeze-drying method. By utilizing the two-dimensional nanoconfinement effect to confine the free diffusion of CO intermediates between the layers, this structure enhances their local concentration and promotes C–C coupling, thereby doubling the selectivity for converting CO₂ into C₂ products in electrocatalysis [56]. Xie achieved more effective confinement of AuCu bimetallic nanoparticles within (ethylene diamine tetraacetic acid) EDTA-modified UiO-66 (a typical MOF (metal organic framework)) by utilizing MOF channels to restrict metal growth, significantly reducing the particle size and enriching the oxygen vacancies, thereby enhancing the catalytic activity for CO₂ hydrogenation to methanol with a 3.21-fold improvement in methanol space-time yield [57]. Wang’s team induced the spontaneous dispersion of In₂O₃ nanoparticles into ultrathin InO_x layers on TiO₂ surfaces, forming In–O–Ti bonds while suppressing the over-reduction of In₂O₃ to metallic In. This strategy significantly enhanced the catalytic stability of CO₂ hydrogenation (over 20-fold) and demonstrated the universality of the interface confinement effect across diverse oxide supports [58].

A considerable volume of research has been undertaken in recent years on various nanoconfined catalytic materials. The search for new nanoconfined catalytic materials with superior functionality remains a primary focus in the domain of carbon reduction capacity. In this review, we mainly introduced the recent progress of nanoconfined catalysts in CO₂, CH₄ conversion. The nanoconfined catalysts were classified and summarized from the dimensional perspective, and their characteristics were introduced. The synthesis and improvement strategies of various nanoconfined catalysts were discussed. Finally, the challenges faced by nanoconfined catalysts and their prospects for the future are summarized (Figure 1b).

2. Nanoconfined Catalysis

Xinhe Bao proposed the concept of “nanoconfined catalysis”, which establishes intrinsic correlations between catalyst structure, properties, and catalytic performance within spatially confined nanodomains. The confinement effect can be conceptually understood as a spatial phenomenon where nanocavities impose geometric constraints on guest molecules. Furthermore, electronic interactions or interface bonding between the nanocavity wall and the guest can regulate their atomic and electronic structures. This results in the formation of metastable structures that exhibit enhanced reactivity. Associated microenvironmental effects encompass the mass transfer effect, metal size effect, void confinement effect, spatial compartmentation effect, and surface modification effect [59].

Analyzing nanoconfined catalytic structures and properties often requires characterization tools. Scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) provides high-resolution surface morphology analysis, combined with energy-dispersive spectroscopy for rapid detection of elemental composition and distribution, making it applicable for observing particle morphology, size, and surface elemental distribution. Transmission electron microscope (TEM) utilizes electron beam penetration to reveal nanoscale crystal structures, lattice arrangements, defects, and interfacial characteristics. The integration of these techniques comprehensively analyzes the microstructure, chemical composition, and physical properties of materials, offering critical data support for material design, performance optimization, and nanotechnology research. Above all, these characterization tools can detect the particle size distribution of metal nanoparticles, which directly influences the density of catalytic active sites. A uniform distribution optimizes surface atom utilization, enhancing reaction selectivity and efficiency. Simultaneously, uniformity strengthens structural stability, reduces sintering, and ensures efficient mass transfer and electron transport in nanoconfined environments.

2.1. One-Dimensional Nanoconfined Catalysis

1D nanoconfined catalysis refers to catalytic reactions occurring within longitudinally nanostructured confined spaces (e.g., nanotubes, nanochannels), where spatial confinement regulates electron dynamics and reactant mass transport to enhance catalytic performance. The fundamental principle underlying this phenomenon pertains to the observation that the nanoconfined space, typically measured in nanometers, exerts a profound influence on the electronic structure of the catalyst. This influence is manifested through the imposition of geometrical constraints, forming a built-in electric field. The consequence of this field is the promotion of photogenerated carrier separation, a process that is particularly salient in photocatalytic systems. Concurrently, the electric field exerts a nanoconfined influence on the migration and agglomeration of the metal nanoparticles, thereby ensuring the maintenance of a high dispersion of the active sites. Generally, one-dimensional nanoconfined catalysis has three characteristics: directed mass transfer, electron regulation, and confined enrichment [60,61,62].

One-dimensional nanoconfined structures synergistically modulate active site microenvironments via spatial confinement effects, significantly enhancing catalytic stability, anti-sintering resistance, and substrate-selective activation capabilities, thereby offering a universal strategy for designing efficient heterogeneous catalysts. Therefore, Liu et al. developed a bifunctional Pb-K metal–organic framework (NUC-45) constructed from S-shaped [Pb₁₀K₂(μ₂-OH)₂(COO)₂₄] clusters, featuring 1D open channels along the a-axis [63]. The NUC-45 architecture comprises robust 3D frameworks formed by {Pb₁₀K₂} clusters and TDP⁶⁻ ligands, where each cluster is encircled by five quasi-rectangular 1D channels (Figure 2a–c). This 1D confinement system enhances catalytic performance by enriching Lewis acid sites (Pb²⁺, K⁺) and basic sites (μ₂-OH, pyridinic N) within the nanochannels, creating synergistic catalytic microenvironments. SEM-EDS analysis confirmed the morphological characteristics of the synthesized crystals (Figure 2d). Physical confinement in the 1D architecture stabilizes reaction intermediates, endowing the catalyst with exceptional cyclability in CO₂-epoxide cycloaddition and Knoevenagel condensation reactions (Figure 2e,f). Li et al. achieved precise confinement of Ni nanoparticles within SiO₂ nanotubes via a core-shell design strategy [64]. The researchers successfully constructed NiPhy@SiO₂ core-shell one-dimensional nanotubes by using nickel-layered silicate (NiPhy) nanotubes as structural templates and coating SiO₂ shell layers on their surfaces. During the subsequent reduction process by high-temperature heat treatment, the thermal decomposition reaction of the NiPhy core layer occurred, generating nickel metal nanoparticles with a uniform particle size, which were confined inside the one-dimensional channels of the SiO₂ nanotubes (Figure 2g). Combined physical confinement by SiO₂ walls and in situ formed SiO₂ nanoparticles effectively suppressed Ni migration and sintering while strengthening metal-support interactions. The confined structure demonstrated remarkable anti-sintering and coking resistance during dry methane reforming, with 7.6 nm Ni nanoparticles uniformly distributed in SiO₂ channels and minimal carbon deposition after 70 h operation (Figure 2h,i). Xue et al. engineered SNNU-33s materials with 4.6 Å 1D confined pores by incorporating C₃-symmetric [Cu(pyz)₃] units into MIL-88-type MOF channels through pore-space partitioning (Figure 2j–m) [65]. The synergy between confinement effects and Cu⁺ π-complexation markedly improved selective adsorption of unsaturated hydrocarbons. Hydroxyl-functionalized SNNU-33b demonstrated an ideal adsorption solution theoretical selectivity value of 597.4 for C₂H₂/CH₄, confirming its exceptional dynamic separation performance. Sergei A. Chernyak et al. developed a 1D confined catalysis system for CO₂ hydrogenation via spark plasma sintering (SPS) densification of Fe oxide-decorated carbon nanotubes (CNTs) [66]. XRD analysis revealed confinement-enhanced metal-support interactions that facilitated Fe carburization into active χ-Fe₅C₂ phases (Figure 2n). Concurrently, carbon shells stabilized nanoparticles and optimized CO intermediate diffusion/activation (Figure 2o). TEM imaging demonstrated that dense CNT frameworks physically suppressed Fe sintering, ensuring catalytic stability (Figure 2p,q).

The Zhang team developed a carbon nanotube (CNT)-confined bimetallic alloy catalyst (FeNi@CNTs) for the photothermal catalytic oxidative dehydrogenation of ethane with CO₂ (ODEC) to efficiently produce ethylene [67]. First, Prussian blue analog (PBA) precursors were electrostatically self-assembled on carbon nitride (C₃N₄) nanosheets. The PBA/C₃N₄ precursor was then calcined under a N₂ atmosphere, enabling carbothermal reduction and directional growth of CNTs to form CNT-encapsulated alloy nanoparticles (FeNi) (Figure 3a). Transmission electron microscopy (TEM) revealed FeNi alloy nanoparticles (~20 nm in size) confined within bamboo-like CNTs, with a lattice spacing of 0.21 nm corresponding to the (111) crystal plane of the FeNi alloy (Figure 3b–e). XRD patterns showed a shifted (111) diffraction peak at 43.87° for FeNi@CNTs compared to the monometallic Ni (111) peak at 44.28°, further confirming FeNi alloy formation (Figure 3f). Extended X-ray absorption fine structure (EXAFS) analysis verified the presence of Ni–Fe bonds (bond length: 2.2 Å) in the alloy (Figure 3g). Performance tests demonstrated that the FeNi@CNTs achieved an ethylene production rate of 768 μmol/h/g, significantly surpassing monometallic and other bimetallic catalysts (Figure 3h). The researchers also investigated the wavelength-dependent selectivity of the catalyst (Figure 3i,j). Experimental results and simulations revealed that UV light excitation generated high-energy hot carriers, driving CO₂ reduction and ethane oxidative dehydrogenation. Visible light in the 420–490 nm range promoted non-oxidative dehydrogenation to ethylene, while light >490 nm caused hot carrier decay into thermal energy, predominantly triggering ethane cracking to CH₄. Niu et al. [68] reported a dual-chainmail-structured Ni-based catalyst (Ni@NC@NCNT), where Ni nanoparticles were doubly encapsulated by N-doped carbon layers and carbon nanotubes, synthesized via a solvothermal–evaporation–calcination method for efficient and stable CO₂ electroreduction to CO (Figure 4a). High-resolution TEM images revealed that Ni particles were wrapped by carbon layers (2–3 nm) and carbon nanotube walls (4–5 nm), with lattice fringes corresponding to graphitic carbon (0.34 nm) and metallic Ni (0.20 nm), confirming the dual-chainmail structure (Figure 4b–d). Performance analysis showed that linear sweep voltammetry (LSV) curves achieved a high current density of 48.0 mA cm⁻² at −1.10 V in CO₂-saturated electrolyte (Figure 4e). Ni@NC@NCNT exhibited a CO Faradaic efficiency of 94.1% at −0.75 V (Figure 4f). Structurally, the catalyst possessed a high specific surface area (240.4 m²/g) and abundant pyridinic N active sites (Figure 4g–i). From the nanoconfinement perspective, the negligible difference in FE_CO (Faradaic efficiency) between buffered and unbuffered electrolytes confirmed that the nanotube confinement effect maintained a local high pH to suppress hydrogen evolution reactions (HERs) (Figure 4j). When investigating the CO₂ reaction pathway, the near-zero reaction order of HCO₃⁻ indicated that protons derived from HCO₃⁻ were not involved in the rate-determining step (Figure 4k). Thus, the reaction proceeds through a stepwise electron-proton process to form *COOH, followed by a second electron–proton step releasing CO, with the initial proton-decoupled single-electron process identified as the rate-determining step (Figure 4l).

2.2. Two-Dimensional Nanoconfined Catalysis

2D nanoconfined catalysis involves catalytic reactions within nanoscale-confined spaces at interlayers or interfaces of two-dimensional materials (e.g., nanosheets, graphene, transition metal dichalcogenides), governed by geometric confinement and electronic modulation principles. The confinement of active sites (e.g., metal clusters, single atoms) within two-dimensional interlayers has been demonstrated to stabilize reaction intermediates through geometric constraints while concomitantly suppressing component aggregation. Concurrently, the modulation of the electronic structure via d-band center adjustment and the formation of a built-in electric field has been shown to enhance electron transfer efficiency. This is exemplified by graphene overlayer–substrate interactions, which optimize intermediate adsorption through electron tunneling effects. The following four points concisely summarize the characteristics of 2D nanoconfined catalysis: directed mass transfer and efficient diffusion, electronic structure modulation, high stability, and intermediate stabilization and selectivity enhancement [69,70,71].

Two-dimensional nanoconfined structures achieve precise modulation of active site microenvironments through the synergistic interplay of spatial constraints and electronic state coupling, significantly enhancing catalytic reaction kinetics, product selectivity, and mass transfer behaviors, thereby offering multi-scale cooperative strategies for optimizing energy–mass transport and conversion efficiency in heterogeneous catalytic systems. Consequently, Li et al. pioneered and experimentally validated the novel concept of overlayer-confined catalysis using 2D materials [72]. Density functional theory (DFT) calculations on graphene/Pt(111) systems revealed that confined spaces between 2D overlayers and metal surfaces reduce adsorption energies (e.g., CO adsorption by 0.44 eV) through combined geometric constraints and confinement field effects. Chen et al. investigated graphdiyne (GDY)-coated copper surfaces for enhanced CO₂ electroreduction under 2D confinement conditions [73]. DFT analysis demonstrated that GDY–Cu interfacial confinement lowers the free energies of key intermediates (COOH* and CHO*), significantly boosting catalytic activity. Meanwhile, analysis of the density-functional energy distribution and DFT potential energy surface maps indicates that CO₂ crosses the GDY with a low potential barrier (0.15 eV) and is stable at room temperature. In addition, CO escapes with a high potential barrier (1.12 eV), while CH₄ escapes easily with a low potential barrier (0.31 eV). Furthermore, the GDY pores promote efficient CO₂ reduction (Figure 5a,b). Song et al. developed an all-organic 2D CN-COF-TD heterojunction catalyst for efficient photocatalytic CO₂ reduction [74]. The two-dimensional nanoconfined domain effect plays a pivotal role in this system: the layered structure of 2D CN provides a high specific surface and abundant active sites, while the microporous structure of COF-TD promotes CO₂ adsorption and activation through spatial nanoconfinement (Figure 5c). The van der Waals force-driven heterojunction interface has been demonstrated to form a tight π–π stack. This has been shown to significantly enhance the photogenerated carrier separation efficiency. In addition, the nanoconfined effect has been shown to shorten the charge migration path and reduce the complexation rate (Figure 5d). Experimental evidence demonstrated that the heterojunction band gap is reduced to 2.63 eV, the visible light response range is expanded, and the CO yield is enhanced by 9.2-fold compared with that of a single component (Figure 5e,f). Chen et al. demonstrated a 2D confinement-based membrane technology for efficient CO₂ separation [75]. The researchers subjected MoS₂ nanosheets to a chemical exfoliation process, subsequently assembling them into lamellar membranes through vacuum filtration. Thereafter, they infiltrated ionic liquids [BMIM][BF₄] into the two-dimensional channels of MoS₂ (Figure 5g). SEM revealed a lamellar stacked structure of a MoS₂ membrane with interlayer expansion and surface continuity after infiltration of ionic liquid, thereby demonstrating the successful filling of the two-dimensional channels (Figure 5h–k). Atomic force microscopy was utilized to ascertain the thickness of the monolayer of MoS₂, which was found to be approximately 1.2 nm, thereby confirming the efficacy of the exfoliation process (Figure 5l). Experimental findings have demonstrated that the solidification point of the ionic liquid within a nanoconfined environment is elevated, and the vibrational spectra exhibit a shift, indicating a robust interaction with the MoS₂ interface (Figure 5m,n). Fu et al. engineered all-organic 0D/2D heterostructures to harness 2D nanoconfinement effects for photocatalytic CO₂ reduction [76]. The researchers utilized an ultrasonication technique to amalgamate porous g-C₃N₄ with xBC ethanol solution, followed by stirring and centrifugation, and subsequently dried to yield 0D/2D heterojunctions (Figure 5o). The synergistic effect of the 2D nanoconfined environment and molecular-level structural modulation resulted in a CO yield of 2BCN that was up to 23.9 times that of PCN. Furthermore, the photocatalytic activity of the 2BCN samples did not increase with an increase in 2BC loading, thereby revealing the precise modulation mechanism of the 2D material-nanoconfined effect on the electronic microenvironment of the active site of the quantum dots (Figure 5p). Wei et al. investigated syngas conversion mechanisms at graphene-confined Cu(111) interfaces [77]. The proposed structural model of graphene-covered Cu(111) interfaces provides a geometrical explanation of the two central mechanisms in 2D nanoconfined interfaces: the electron transfer effect, which is manifested in the unidirectional charge redistribution from graphene to the Cu substrate; and the spatial confinement effect, whose mechanism of action stems from the physical nanoconfinement of the orientational degrees of freedom of the reactive intermediates and the diffusion paths (Figure 5q). The turnover frequency (TOF) for CH₄ generation at 530 K demonstrated a consistent 2.5-fold enhancement over C₂H₅OH with increasing pressure, while gradual convergence was observed with rising temperature. This trend was accompanied by a monotonic TOF decline above the threshold pressure of 32 bar, revealing mass-transport constraints imposed by nanoconfinement effects (Figure 5r).

Fan et al. [56] reported a novel sandwich-structured catalyst (C/Cu/C) prepared via a bidirectional freezing-freeze-drying method, which features reduced graphene oxide (rGO)-encapsulated Cu nanowires in a layered architecture for efficient electrocatalytic CO₂ conversion to C₂ products (Figure 6a). The rGO layers form a physical barrier to restrict the free diffusion of *CO intermediates, significantly enhancing their local concentration compared to disordered mixtures, thereby promoting C–C coupling to generate C₂ products (e.g., ethanol, ethylene) (Figure 6b–e). SEM and TEM images revealed the layered arrangement and porous structure of the sandwich architecture, with nanosized Cu uniformly embedded between rGO layers (Figure 6f,g). XRD patterns confirmed the presence of rGO (broad peak at ~27°) and the (111) crystal plane of Cu (2θ = 43.3°), further verifying the sandwich structure (Figure 6h). The catalyst achieved a C₂ Faradaic efficiency (FE) of 47% at 200 mA cm⁻², nearly double that of the disordered mixture (25%) (Figure 6i). In situ FTIR spectra showed a distinct *CO characteristic peak at 2146 cm⁻¹ for the sandwich structure, indicating *CO enrichment, whereas the disordered mixture exhibited a *CHO peak at 1742 cm⁻¹, corresponding to increased CH₄ production (Figure 6j,k). These characterizations collectively demonstrated that in disordered mixtures, *CO freely diffused into the electrolyte bulk, while in the sandwich structure, *CO was confined between layers, facilitating C–C coupling for enhanced C₂ product formation (Figure 6l).

2.3. Three-Dimensional Nanoconfined Catalysis

Three-dimensional nanoconfined catalysis is a catalytic reaction in a nanoconfined space characterized by a porous or layered structure. Examples of such structures include a three-dimensional porous membrane or a nanoparticle-filled system. The electronic structure and reaction mass-transfer pathway are regulated by the three-dimensional spatial confinement effect and interfacial synergism, thereby achieving efficient and precise catalytic performance. The fundamental principle underlying this phenomenon pertains to the observation that the three-dimensional nanoconfined space (e.g., nanopores, interlayer channels) exerts a significant influence on the electronic energy states (e.g., valence electron orbital properties) of the catalysts. This influence is facilitated by geometric constraints, resulting in the formation of a localized high-concentration reaction environment. Concurrently, this process reduces the migration distance of free radicals and stabilizes the active sites. The characteristics of 3D nanoconfined domain catalysis can be summarized as follows: electronic structure modulation, high specific surface area and mass transfer optimization, spatial stabilization, and efficient radical utilization [78,79,80,81,82,83].

Three-dimensional nanoconfined catalysis optimizes interfacial and pore characteristics through microstructural modulation, significantly enhancing gas conversion/separation efficiency, thereby providing high-efficiency strategies for green energy technology development. Xia et al. engineered a sunflower-like WO₃/ZnIn₂S₄ heterojunction with 3D confinement effects for efficient CO₂ reduction [84]. The 3D core-shell confined architecture synergized cavity-mediated CO₂ enrichment with S-scheme heterojunction charge transfer, achieving 82.1% CH₄ selectivity in photocatalytic reduction through enhanced carrier separation (Figure 7a). SEM imaging revealed the integration of WO₃ hollow sphere cores (300 nm) with petal-like ZnIn₂S₄ nanosheet shells (Figure 7b). The TEM and HRTEM analyses confirmed the 3D/2D heterogeneous interface and identified 0.369 nm (W) and 0.294 nm (ZIS) lattice fringes (Figure 7c,d). The EDS elemental distributions revealed that W/O is enriched in the inner core and Zn/In/S is distributed in the outer layers, thereby forming a spatially confined domain structure (Figure 7e). Guan et al. developed 3D ionic liquid-confined COFs (3D-IL-COFs) under normal pressure and temperature for selective CO₂/CH₄ separation [85]. As shown in Figure 7f, topological structure analysis and pore size distribution analysis revealed that 3D-IL-COF-3 is constructed by an 11-fold interpenetrated diameter net with the highest interpenetrated extent reported so far in the system of COFs. SEM characterization showed 3D-IL-COF-3 crystals (0.5–1.0 μm) forming intricate aggregates (Figure 7g). Breakthrough curves demonstrated exclusive CO₂ retention in 3D-IL-COF-1 pores versus unimpeded N₂/CH₄ passage (Figure 7h,i), validating IL-COF’s molecular sieving capability and providing new ideas for the green and efficient preparation of nanoconfined catalytic materials. Zhang et al. fabricated MOF-derived 1D/3D nitrogen-doped porous carbon (NPC) architectures for syngas production via CO₂ electroreduction [86]. The researchers grew Zn-MOF-74 crystals in situ using a melamine sponge (MS) as a three-dimensional scaffold, which was carbonized to form a composite structure consisting of 1D carbon rods (MOF-derived) with 3D nitrogen-doped porous carbon networks (Figure 7j). SEM maps (Figure 7k–m), TEM analyses (Figure 7n–p) and elemental mapping images (Figure 7q) of the 1D/3D NPC-1000 after carbonization show the uniform loading of the 3D skeleton with one-dimensional carbon rods, the coexistence characteristics of ordered graphitic carbon/amorphous carbon and the uniform distribution of nitrogen. Zhang et al. engineered Fe₃O₄-FeC_x heterojunctions within N-doped ordered mesoporous carbon (N-OMC) for efficient CO₂-to-olefin conversion [87]. Figure 7r depicts the two-step synthesis: precursor blending followed by staged carbonization to construct confined Fe₃O₄-FeC_x/N-OMC catalysts. The difference in the reaction mechanism of CO₂ hydrogenation on 0.8Fe-0.1K/N-OMC and 0.8Fe-0.1K@N-OMC reveals that the heterojunction-confined domain structure promotes the overflow of CO from Fe₃O₄ to the neighboring FeC_x sites to achieve the efficient synergy between reverse water gas shift (RWGS) and Fischer–Tröpsch synthesis (FTS) (Figure 7s,t).

Taking it one step further, Zhao et al. developed a 3D nanoconfined Bi@np-Cu catalyst with bismuth nanoparticles confined in nanoporous copper for efficient CO₂ electroreduction [88]. The 3D interconnected nanoporous copper framework was fabricated via selective dealloying, in situ growth, and electrochemical reconstruction (Figure 8a). SEM imaging revealed uniformly dispersed Bi nanoparticles (about 20 nm) on the np-Cu scaffold without agglomeration (Figure 8b,c). High-resolution transition electron microscopy (TEM/HR-TEM) analyses identified heterointerfaces between Cu(111) (d-spacing: 0.21 nm) and Bi(110) (0.23 nm) (Figure 8d). EDX mapping confirmed the three-dimensional spatial confinement of the Bi and Cu elements (Figure 8e). This demonstrates the critical role of 3D confinement in enhancing catalyst dispersion, stability and interfacial electronic effects. In the study by Zhu et al. [89], a hierarchical heterostructure of 0D CdS quantum dots confined in 3D ZnIn₂S₄ nanoflowers was constructed by means of a two-step solvothermal method for efficient photocatalytic CO₂ reduction (Figure 8f). SEM revealed three-dimensional nanoflower structures (Figure 8g–i). TEM and HRTEM confirmed the uniform dispersion of CdS quantum dots (0.34 nm lattice) on the surface of ZnIn₂S₄ nanosheets (0.32 nm lattice) (Figure 8j–l). The formation of the 3D ZnIn₂S₄ nanoflowers is attributed to the self-assembly of the 2D nanosheets, resulting in a porous hierarchical structure. This structure is characterized by a high specific surface area and many CO₂ adsorption sites. Additionally, it enhances the light trapping ability through multiple light scattering. The 0D CdS quantum dots are uniformly anchored on the surface of the 3D skeleton to form a strong interfacial coupling, and the quantum confinement effect is utilized to modulate the electronic energy level structure and promote the directional migration of ZnIn₂S₄ conduction-band electrons to CdS. Peng et al. designed a 3D honeycomb-like N-doped carbon cloth electrode (Cu₁Sn₄-N-CC) with bimetallic Cu/Sn loading [90]. Figure 8m illustrates the synthesis of copper and tin alloy catalysts on N-doped porous carbon cloth by an electro-deposition strategy. Figure 8n presents the macroscopic morphologies of electrodes with different Cu/Sn molar ratios: Cu-N-CC appears dark red, Sn-N-CC is silver gray, and Cu/Sn alloy electrodes (such as Cu₁Sn₄-N-CC) are brownish gray, intuitively reflecting the regulation of electrode color by the metal ratio. Yan et al. constructed three-dimensional porous organic frameworks (3D-NiSAs/NiNCs-POPs) in which nickel single atoms (Ni SAs) and nickel nanoclusters (Ni NCs) were simultaneously loaded to enhance the CO₂ photocatalytic performance [91]. Average bond lengths of 2.1 Å (Ni–O) and 2.0 Å (Ni–N) were found in the 3D-NiSAs-POPs. Wavelet-transform EXAFS contour plots confirmed the coexistence of Ni-N/O sites and Ni-NCs in the 3D-NiSAs/NiNCs-POPs (Figure 8o,p). The researchers also proposed a possible mechanism for 3D-NiSAs/NiNCs-POP-catalyzed CO₂ photoreduction: Ni single atoms and clusters synergistically photocatalyze CO₂ reduction by asymmetric adsorption, electron transfer, and optimized intermediate binding to lower the energy barrier (Figure 8q). Zhang et al. developed Pt/FeNC composite cathodes with 3D confinement effects for high-performance Li-CO₂/O₂ batteries [92]. Cubic FeNC frameworks embedded with FeC nanoparticles (0.25 nm lattice) were characterized (Figure 8r–t). The Pt/FeNC maintains a cubic morphology with 2.4 nm Pt nanoparticles loaded uniformly on the surface of carbon flakes, and HRTEM confirmed the Pt(111) crystalline facets (0.23 nm spacing), revealing the spatial nanoconfined effect of the three-dimensional porous carbon carriers on Pt (Figure 8u–w).

2.4. Interfacial Nanoconfined Catalysis

Interfacial nanoconfined catalysis is a broad category encompassing 1D/2D/3D systems, operating through nanoscale interface structures that precisely modulate electronic states and geometric configurations of catalytic active centers. Specifically, ligand-unsaturated active sites (e.g., the In-O-Ti bonding interface of In₂O₃ nanolayers with TiO₂) are formed through the interlayer-confined domain space of metal–oxide interfaces or layered materials. The interfacial electron penetration effect and geometrical constraints are utilized to change the center position of the d-band of the catalysts to optimize the intermediate adsorption energy. Three defining features characterize interfacial nanoconfined catalysis: electron modulation dominance, enhanced mass transfer efficiency, and chemically bonded interfaces [49,93,94,95,96].

Researchers have significantly enhanced gas conversion efficiency and product selectivity by modulating interfacial electronic states and active site distributions through nanoconfinement strategies, thereby offering innovative directions for designing green energy catalytic systems. TiO₂ exhibits low activity in CO₂ hydrogenation with difficulty in generating surface oxygen vacancies, requiring combination with active components to enhance catalytic performance [97,98]. Cubic-phase In₂O₃ offers advantages in RWGS, including stronger H₂ dissociation and adsorption, facile oxygen vacancy formation, and efficient CO₂ activation [99]. Studies on In₂O₃ and supported In₂O₃ catalysts have attracted significant attention in CO₂ hydrogenation reactions [58,100,101]. Among them, Wang et al. elucidated the regulatory mechanisms of interfacial nanoconfined effects on CO₂ hydrogenation reactions [58]. Under the H₂/CO₂ atmosphere, In₂O₃ nanoparticles dynamically disperse into ultrathin InO_x nanolayers on TiO₂ supports, forming In–O–Ti interfacial bonds (Figure 9a). As illustrated in Figure 9b, the cross-sectional HRTEM image of the TiO₂@InO_x catalyst reveals that the thickness of the InO_x nanolayer is measured at 0.6–0.7 nm (~2–3 atomic layers). This observation indicates that In₂O₃ forms an ultrathin overlayer on the surface of TiO₂, closely approaching the monolayer limit. As demonstrated in the wavelet transformed (WT) extended EXAFS spectra (Figure 9c,d), the In–O and In–O–In bonds experience a reduction in strength following the reaction, concomitant with the emergence of the In–O–Ti bond. This observation serves as evidence for forming an InO_x–TiO₂ interfacial bond, wherein the In–O–Ti bond replaces a proportion of the In–O–In bonds. The interfacial nanoconfined effect stabilizes the stable InO_x structure through electronic interactions, promotes the formation of surface oxygen vacancies, and inhibits the excessive reduction into the metallic state. Consequently, this enhances the CO₂ adsorption activation capacity. As posited by Chen et al. [102], Cu, Zn, and Zr precursors were loaded into the pores of mesoporous silica spheres (MSS) through wet impregnation. Following this process, the creation of confined nanoparticles occurred via calcination and reduction (Figure 9e). The construction of highly dispersed Cu-ZnO, Cu-ZrO_2, and ternary interfacial active sites was achieved by confining the ZnO-Cu-ZrO₂ three-phase interface to less than 3.5 nm pores (Figure 9f,g). The high-resolution TEM images of the reduced (Cu-ZnO-ZrO₂) CZZ-MSS samples (Figure 9h) demonstrate the dispersion of Cu nanoparticles with a stripe spacing of 0.21 nm on the MSS carriers. The methanol spatiotemporal yield of this nanoconfined system was found to be significantly higher than that of the industrial catalyst (Figure 9i). Li et al. engineered Au-θ-Al₂O₃/Au/PCN composites through a synergistic active site structure design for efficient CO₂ photoreduction [103]. Through the process of nanosheet layer intercalation assembly, the PCN establishes close proximity with the Au-θ-Al₂O₃ interface, thereby constructing a multilevel built-in electric field and promoting the spatial separation of photogenerated carriers. The atomically dispersed Au atomic energy, confined by oxygen vacancies in Au-θ-Al₂O₃/Au, provides a substantial number of effective active sites for the CO₂R reaction. The TEM and HAADF images demonstrate that the Au-θ-Al₂O₃/Au nanosheets are closely wrapped by the PCN layer, thereby forming a face-to-face contact heterojunction. Furthermore, the elemental mapping revealed that C, N, O, Al, and Au are distributed uniformly, with Au existing both in the atomic state (θ-Al₂O₃ oxygen vacancies-confined domain) and in nanoparticle form (Figure 9j,k).

Further onwards, Bao et al. synthesized PCN-222 via solvothermal methods, then precisely anchored Cu nanoparticles onto its Zr₆-oxo clusters through ion exchange to construct the Cu@PCN-222 catalyst (Figure 10a) [104]. FESEM and TEM analyses confirmed the retained rod-like morphology of PCN-222 with highly dispersed Cu nanoparticles (Figure 10b,c). EDX mapping demonstrated uniform Cu distribution, verifying successful anchoring on Zr₆-oxo clusters (Figure 10d). Strong metal-support interactions (SMSI) between Zr₆-oxo clusters and Cu generated abundant interfacial active sites, including Zr⁴⁺-O²⁻-Cu²⁺ and Zr⁴⁺-Cu²⁺ configurations. Bu et al. innovatively integrated hexagonal boron nitride (h-BN) with (Ni, Mg)Al₂O₄ nanosheets derived from layered double hydroxides (LDHs), establishing a 2D interfacial confinement architecture [105]. Figure 10e illustrates the reaction mechanism of NiMA-BN-M-R catalysts in methane dry reforming. The presence of highly dispersed Ni nanoparticles has been shown to promote the dissociation of CH₄ to CH_x*, with CO₂ forming carbonate and hydroxyl species at the interface. These react with CH_x* to produce CO/H₂ while inhibiting carbon buildup. Figure 10f shows by cross-sectional SEM and EDX line scanning that the h-BN with the oxide lamellae is distributed alternately with heterogeneous interfaces inhibiting Ni sintering, confirming the structural stability. The characteristic peaks of two carbonate (monodentate and bidentate carbonate) species did not completely disappear, indicating that the NiMA-BN-M-R catalyst has good adsorption and activation capacity for CO₂ (Figure 10g). Long et al. developed a novel composite catalyst featuring hollow sulfur-doped carbon shells encapsulating CoFe alloys (CoFe@CS) [106]. Figure 10h outlines the synthesis: CoFeHCF precursors self-assembled with S²⁻, followed by high-temperature calcination to form hollow multilayered carbon shells around CoFe alloys, with acid washing yielding CoFe@CS. As illustrated in Figure 10i, the electrostatic potential distribution of sulfur-doped and defective regions exhibits stronger positive potentials, verifying that sulfur doping enhances the electron absorption and transport capacity and optimizes the catalytic performance by altering the electron distribution. SEM images demonstrate that CoFe@CS is an irregular spherical particle, with a significantly larger particle size than undoped CoFe@C. TEM images reveal the core-shell structure: the CoFe alloy core (lattice spacing of 0.20 nm) is wrapped by a multilayered, ultrathin carbon shell (the distance between graphite layers is 0.34 nm), which is characterized by porous properties (Figure 10j,k). The elemental distribution map confirmed that the core region is enriched with Co/Fe, C is uniformly distributed, and S overlaps with C, indicating that S has been successfully doped into the carbon skeleton (Figure 10l,m).

2.5. Systematic Evaluation

As an advanced catalytic technology, nanoconfined catalysis demonstrates promising potential primarily due to the microenvironment constructed by its nanoconfined structures. However, this system inherently involves high complexity, encompassing diverse interactions among active component particles, confined frameworks, and reactant molecules. Considering that dimensional features often exhibit distinct performance variations, we concisely summarized their shared advantages and outlined the limitations specific to each dimension to enhance the understanding of the microstructural characteristics of nanoconfined catalysis (

Table 1. Systematic evaluation of the advantages and limitations of nanoconfined catalysis across different dimensions.

Dimension	Typical Structure	Common Advantage	Limitation
1D	Carbon nanotube	Mass transfer effect	Diffusion issues caused by non-uniform pore sizes
2D	Graphene overlayer	Spatial compartmentation effect	The overlayer requires high mechanical stability
3D	MOFs	Surface modification effect	High-temperature structural collapse risk
Interface	Metal–oxide heterojunction	Metal size effect	Scalability challenges in manufacturing

).

Compared to other structural types of catalysts, nanoconfined catalysts exhibit enhanced local concentrations of active components or reaction intermediates due to their confined architecture, whereas disordered heterogeneous or homogeneous catalysts lack this capability, resulting in distinct product selectivity compared to traditional catalytic systems [56,67,107,108,109,110]. Additionally, nanoconfinement improves the sintering resistance of active components, thereby enhancing the overall stability of the catalytic system for long-term carbon-based energy conversion [51,64,66,105,108,111]. However, the industrialization of nanoconfined catalysts still lags behind traditional catalysts due to their complex synthesis processes and high raw material costs, which are major concerns for industries. Consequently, recent explorations into low-cost nanoconfined catalytic systems hold greater research value and significance.

3. Synthesis and Optimization Strategy for Nanoconfined Catalysts

3.1. Heteroatom Doping Engineering

Heteroatom doping engineering is a process that enables the targeted modulation of catalytic performance. This is achieved by the introduction of heterogeneous atoms into the nanoconfined catalytic system, resulting in the reconfiguration of the electronic structure and coordination microenvironment of materials from the atomic scale. Heteroatoms have been shown to enhance the adsorption strength and selectivity of the active sites for key intermediates by modifying the charge distribution of the host material (e.g., inducing charge polarization or localized electron enrichment). As a result, reaction barriers are reduced and reaction paths are modulated. Simultaneously, the dopant atoms form specific chemical bonds with metallic or non-metallic components in the nanoconfined space. This can stabilize the geometrical configuration of the active sites, thereby inhibiting agglomeration or deactivation. Furthermore, it can synergize with the nanoconfined effect to enhance the mass-transfer kinetics and promote the rapid directional diffusion of the reactants within the nanochannels [112,113,114,115]. This atomic-level electron-geometry dual-regulation mechanism enables heteroatom doping to overcome the limitations of traditional catalytic materials in terms of the trade-offs among activity, selectivity, and stability. It also provides a means of regulation with molecular-level precision for the rational design of efficient nanoconfined-domain catalytic systems [116,117,118,119,120].

The precise regulation of interfacial electronic states and active site distributions through heteroatom doping and synergistic nanoconfinement strategies significantly enhances carbon-based energy conversion efficiency and product selectivity. Chen et al. have significantly demonstrated a substantial enhancement of the CO₂ electroreduction properties of In₂O₃ nanocrystals. This advancement has been achieved by implementing a synergistic strategy incorporating nickel doping and the introduction of carbon-confined domains [121]. Nickel-doped In₂O₃ nanocrystals were encapsulated within carbon fibers via electrospinning–carbonization methods (Figure 11a). HRTEM revealed the (111) crystal surface of In₂O₃ (0.29 nm lattice stripe). HAADF-STEM and EDX elemental distribution maps demonstrated the uniform distribution of Ni, In, and O within the nanocrystals, with complete encapsulation of the carbon fibers (Figure 11b,c). Nickel doping has been shown to optimize the electronic structure of In₂O₃, thereby improving the electrical conductivity of the catalyst. In addition, nickel doping has been demonstrated to accelerate the charge transfer rate of the electrocatalytic reaction (Figure 11d,e). Zang et al. engineered a confined interfacial catalyst (Cu-N-G) via nitrogen-doped graphene-coated copper foam to synergistically regulate CO₂ electroreduction pathways [122]. Graphene was grown on copper foam via chemical vapor deposition (CVD), followed by ammonia treatment for nitrogen doping (Figure 11f). SEM analysis revealed that the Cu surface of the foam was enveloped by folded graphene, thereby establishing a three-dimensional conductive network (Figure 11g,h). Among them, a Cu-N-G hydrophobic surface (113.5°) was found to impede the hydrogen evolution reaction (Figure 11i). EDX elemental mapping verified a uniform C/N/Cu distribution and successful nitrogen incorporation (Figure 11j). X-ray photoelectron spectroscopy (XPS) analysis confirmed that nitrogen doping elevates the average valence state of Cu to promote C–C coupling (Figure 11k). DFT simulations revealed interactions between N and CO₂ through charge transfer and adsorption energy optimization, enhancing CO₂ activation. The synergistic effect of doping and nanoconfined significantly improved the ethanol selectivity (FE up to 33.1%), thus revealing the synergistic mechanism of the doped interfacial electronic structure and spatial nanoconfinement on the reaction path. Guo et al. [123] constructed nitrogen-doped hierarchically ordered porous carbon-loaded monoatomic zinc catalysts (Zn-N-HOPCPs) for efficient photocatalysis of CO₂. This was achieved by pyrolyzing ZIF-8 single crystals in the interstitial space of SiO₂ gel–crystal templates via a nanoconfined pyrolysis strategy (Figure 11l). SEM confirmed that template confinement prevented structural collapse during carbonization (Figure 11m). HAADF-STEM and the elemental distribution maps, in conjunction with aberration-corrected HAADF-STEM images, provided unequivocal confirmation of the observation that Zn is firmly anchored in the N-doped hierarchically ordered porous carbon as a solitary atom (Figure 11n–q). The XPS spectra revealed that the N-doped carbon matrix provides pyridinic N sites (398.6 eV) (Figure 11r). The Zn 2p_3/2 (1021.1 eV) and Zn 2p_1/2 (1044.2 eV) orbitals confirmed the presence of isolated Zn sites in Zn-N-HOPCP (Figure 11s). Recent studies demonstrated that single-atom Zn anchored by adjacent N atoms (Zn-N₄ moieties) can be obtained through one-step pyrolysis of ZIF-8 [124,125], thus confirming the formation of atomically dispersed Zn-N₄ acid–base synergistic catalytic centers. Concurrently, the nanoconfined effect ensured the uniform anchoring of Zn atoms to the carbon skeleton, and the graded pores facilitated mass transfer and light trapping for efficient CO₂ photocatalytic conversion under mild conditions.

Additionally, Liu et al. [126] employed the tubular architecture of Ni-salen polymers (Ni-N₂O₂) to pre-anchor metal sites, achieving precise construction of Ni-Ni-N₂O₂ single-atom sites via Ni–O bond cleavage and Ni–C bond formation during pyrolysis (Figure 12a). They observed through high-resolution microscopy (Figure 12b–e) that the Ni-NC derived from pyrolysis with Ni-salen polymer addition exhibited a typical graphene-like structure with abundant surface pores, which facilitates mass transfer during catalytic processes. In conjunction with the elemental distribution analysis, it has been confirmed that Ni is dispersed in the nitrogen-doped carbon matrix through Ni-N₂C₂ coordination. This verifies the precise construction and high loading characteristics of single atomic sites (Figure 12f). Figure 12g–i jointly reveal the high-performance nature of Ni-N₂C₂-p: its unique electronic structure (D-band center shift up) facilitates the formation of COOH intermediates through orbital hybridization (d_yz/d_xz coupling with C-2p). In contrast, the spatial distribution of molecular orbitals (HOMO/LUMO localization) further optimizes the reaction path and ultimately reduces the energy barrier of the decision step (*COOH formation). Chen et al. [111] developed an efficient photothermal catalytic system through synergistic nanoconfinement and heteroatom doping strategies. Using Cu-BTC as a metal-organic framework precursor, the researchers successfully encapsulated Cu-Cu₂O-CuS within a nitrogen-doped porous carbon octahedral matrix via a simple pyrolysis oxidation–sulfidation route (Figure 12j). Additionally, the mechanism for photothermal conversion of CO₂ into CO and CH₄ on the Cu-Cu₂O-CuS@C catalyst has been proposed (Figure 12k). Characterization revealed N-doped carbon octahedrons containing uniformly dispersed Cu-Cu₂O-CuS heterojunctions (Figure 12l–t). We surmise that the enhanced dispersion and the formation of compact heterojunction interfaces might be attributed to the confinement effect inhibiting the rate of sintering and aggregation, while enhancing the formation of heterojunctions within the core-shell structure [127,128,129]. Guo et al. [130] engineered a MOF-derived N-doped carbon-encapsulated Ni catalyst (Ni-MOF@NC) for enhanced CO₂ electroreduction. The Ni-MOF was integrated with VXC-72 carbon black through a solvothermal process in formamide, inducing spontaneous polymerization to yield a nitrogen-doped carbon shell-encapsulated confined architecture. Subsequent pyrolysis of this hybrid precursor resulted in the formation of Ni nanoparticles (Figure 12u). Experiments demonstrate that Ni-MOF@NC maintains over 90% CO Faraday efficiency in a wide potential window of −0.8 to −1.4 V and reaches a peak of 99% at −1.0 V (Figure 12v).

3.2. Defect Engineering

Defect engineering is a process that artificially constructs atomic-level structural defects, such as vacancies, lattice distortions or interfacial mismatches, to confer unique electronic and geometrical regulatory properties on nanoconfined domain catalytic systems. The introduction of defects has been shown to have a significant impact on the local electron distribution within confined spaces (e.g., inducing charge polarization or the formation of unpaired electronic states). Furthermore, it has been demonstrated that this introduction can optimize the adsorption strength and selectivity of the active site to reaction intermediates. In addition, it was also observed that the strong anchoring effect at the defect sites stabilizes the metal nanoparticles or single atoms, thereby inhibiting their migration and aggregation. Furthermore, the defective structures can reconfigure the mass transfer pathways of the nanoconfined channels (for example, by shortening the radical migration distance or forming selective permeation sites), resulting in a synergistic enhancement of the reaction kinetics and substance transport efficiency. The dual regulation of electronic states and microenvironments on the atomic scale renders defect engineering a pivotal strategy for overcoming the limitations of catalytic activity, selectivity, and stability. Furthermore, it provides a dynamically tunable regulatory dimension for the precise design of nanoconfined catalytic systems [131,132,133,134].

Defect engineering synergistically modulates catalyst multiscale architectures with nanoconfinement, optimizing active site local electronic states and reaction-mass transfer pathways, thereby significantly enhancing carbon-based energy conversion kinetics and product selectivity, offering cross-scale cooperative mechanisms for high-performance catalytic systems. Ling et al. achieved defect modulation within MOF-confined spaces via a K⁺-assisted nanoconfinement strategy [135]. The researchers used K⁺ to exchange organic cations in MOF channels to form a nanoconfined environment during the pyrolysis process, and K⁺ achieved synchronous removal of nitrogen dopant and directional construction of intrinsic carbon defects through etching (Figure 13a). As demonstrated by HAADF-STEM images, the nanoconfined domain effect inhibits carbon network remodeling at elevated temperatures, thereby enabling the defective structure to exist stably within the porous carbon skeleton (Figure 13b). Theoretical calculations demonstrated that the nanoconfined-domain electronic environment of V12 defects (V12 is a defect-rich porous carbon with 12 vacancy-type defects, obtained through the pyrolysis of K⁺@bio-MOF-1 at 1100 °C, wherein 12 adjacent carbon atoms are missing) enhanced the CO₂ adsorption capacity, significantly lowered the energy barrier for the formation of COOH* intermediates, and promoted the kinetics of the electrocatalytic CO₂ reduction reaction (Figure 13c,d). This strategy combines defect engineering with nanoconfined-domain catalysis, providing a novel approach for precisely regulating the active sites of carbon-based catalysts. Wang et al. engineered asymmetric channels in helical mesoporous SiO₂ through defect engineering, where surface defects and hydroxyl groups enhanced CO₂ affinity [136]. The researchers elucidated the synthetic pathway of helical mesoporous SiO₂ and the molecular basis of its asymmetric pore structure (Figure 13e). Helical pores (with a diameter of approximately 3.43 nm) of Si-20 form confined spaces (Figure 13f,g). Si-20 has been shown to exhibit selective adsorption of CO₂, facilitated by a combination of factors, including its transportation through a pore wall defect structure and a strong dipolar interaction with hydroxyl groups (Figure 13h). The synergistic effect of defect engineering in conjunction with nanoconfined domains has been shown to enhance the CO₂ permeability of mixed matrix membranes (MMMs) forming a 287.2 barrier while achieving a CO₂/N₂ selectivity of 26.36. This breakthrough surpasses the performance limitations of conventional membrane materials. Wu et al. proposed a novel method for preparing ultra-high-density carbon defects. This method termed the interfacial self-corrosion technique, involves the modulation of defect engineering through the nanoconfined domain strategy [137]. The researchers revealed the regulatory mechanism of the nanoconfined domain effect on CO₂ diffusion and conversion through finite element simulation (Figure 13i). By constructing carbon cavity models (A–F) with different opening angles (30°, 60°, and 90°) in combination with the carrier gas flow rate, it was found that a slight opening angle (30°) and a low flow rate (20 mL/min) could effectively confine the escape of CO₂, which could be retained in the carbon cavity and further react with carbon to generate CO. As demonstrated in Figure 13j, the schematic illustrates that confined CO₂ instigates a self-corrosion reaction at elevated temperatures, thereby continuously removing carbon atoms and forming defects. Density functional theory posits the existence of a gradient “proximity effect” between these defects, with the reduction in spatial distance being conducive to optimizing the electronic structure and diminishing the theoretical overpotential of the oxygen reduction reaction (ORR) (Figure 13k). This study established a quantitative correlation between defect density and catalytic activity, thus providing novel insights into the design of carbon-based catalysts. Wang et al. [138] introduced local defects in UiO-66(ZnZr) via Zn SBU substitution, forming 3D hollow HO-ZnZrO@C through defect-guided contraction during carbonization (Figure 13l). TEM revealed open channels and hierarchical porosity, with HRTEM confirming ~3.5 nm ZnZrO nanoparticles. EDX mapping showed a homogeneous Zn/Zr distribution, while cross-sectional TEM identified mesoporous cavities (Figure 13m–v). The nanoconfined domain effect has been demonstrated to confine ultrafine ZnZrO particles in a hierarchical porous carbon skeleton. It has been shown that the open channels in this configuration enhance mass transfer efficiency, and that the carbon matrix reducibility promotes the enrichment of surface oxygen vacancies and enhances CO adsorption activation. The defects and nanoconfined domains have been shown to synergistically optimize active site exposure and the reaction pathway, thus promoting catalytic performance breakthrough.

3.3. Surface Modification Engineering

The field of surface modification engineering has been shown to enhance the dynamic interaction mechanism between active sites and reactants in the nanoconfined space by modulating the interfacial chemical properties and surface microenvironment of nanoconfined systems. The core function of the system is to introduce specific functional groups or charge distributions at nanoconfined interfaces to precisely regulate the electronic density of states in the active site and the strength of intermediate adsorption. Concurrently, surface modification optimizes the mass transfer kinetics in the nanoconfined channel, reduces the reactant diffusion barrier and enhances the local concentration gradient effect. Furthermore, surface modification engineering has been demonstrated to inhibit the migration and loss of active components through the construction of strong interfacial chemical bonds or spatial site-barrier effects, thereby significantly enhancing the chemical stability of the catalytic system. This modification strategy, founded upon interfacial electronic coupling and mass transfer synergy, integrates the spatial confinement effect of nanoconfined domain catalysis with the depth of surface chemical regulation. This provides a dynamically tunable interfacial regulation dimension for the efficient directed conversion of complex catalytic reactions [139,140,141,142].

Surface modification engineering modulates interfacial electronic states and directional distribution of active sites, thereby optimizing reaction pathways and reducing energy barriers, thus advancing nanoconfined catalysis development. Feng et al. constructed a nanoconfined catalytic system by encapsulating superbase ionic liquid [P66614][Triz] within nickel foam pores through surface modification engineering [143]. The researchers dissolved the super basic ionic liquid [P66614][Triz] in isopropanol and then utilized a drop-coating technique to introduce it into the pores of acid-wash-treated nickel foams. These foams were then subjected to vacuum drying, a process that resulted in the formation of a self-supported catalyst (Figure 14a). SEM maps confirmed the uniform coverage of the nickel skeleton by IL (Figure 14b). N/P elemental distribution maps confirmed the successful loading of IL onto the nickel foam (Figure 14c–e). The ionic liquid modifies the nickel surface by bending and carrying a negative charge (−0.546 e) on the CO₂ molecules through the strong chemical interaction of its superbase anion with CO₂, which significantly reduces the reduction energy barrier (Figure 14f). Yang et al. confined thionine (Th) molecules within platinum nanocrystals via molecular doping, enabling efficient acidic CO₂ electroreduction to methane [37]. In order to synthesize the composite structure of Pt nanocrystalline coated Th in a Th solution, it was necessary to reduce Pt²⁺ in zinc powder. This process was carried out in a single step (Figure 14g). The results of the SEM, TEM and HRTEM analyses showed the “bud” structure of Pt nanocrystals interwoven with Th molecules (Figure 14h–j). The EDX spectra confirmed the uniform distribution of C, N, and S (Th molecular elements) in the Pt matrix, and the molecular confinement was verified (Figure 14k). Theoretical calculations showed that the Th–Pt interface lowers the water decomposition energy barrier (0.43 eV vs. 0.85 eV for pure Pt), increases the *H supply and synergistically modulates the reaction pathway (Figure 14l). You et al. engineered hollow TiO₂@In₂S₃ heterostructures through combined surface modification and nanoconfinement strategies [144]. The construction of the hollow structure was achieved by employing the complex template method (carbon sphere template) in conjunction with the hydrothermal vulcanization method. The shell layer was composed of a TiO₂ composite with In₂S₃ nanoparticles (Figure 14m). Concerning the surface modification, the radial distance of the Ti-O coordination peaks in the WT contour plot of InTi-0.54 was shortened and their intensity was weakened. This directly confirmed the presence of oxygen vacancies and the coordination unsaturated state of Ti, which enhanced the CO₂ adsorption capacity (Figure 14n,o). This nanoconfined spatially synergistic heterojunction effect effectively suppresses photogenerated carrier complexation, demonstrating a synergistic enhancement mechanism between surface modification and spatial confinement. Zhang et al. fabricated 0D/2D SnO₂/g-C₃N₄ heterojunctions via surface modification engineering [145]. The 0D/2D heterojunction is formed by wet chemical mixing of SnCl₂ and melamine, followed by pyrolysis and oxidative etching (Figure 14p). SEM/TEM showed that SnO₂ nanodots (~2 nm) were uniformly loaded on g-C₃N₄ nanosheets, forming a porous layered structure (Figure 14q,r). HAADF-STEM further confirmed the lattice (0.34 nm, corresponding to the SnO₂(110) crystal plane) and size distribution (average ~2 nm) of the SnO₂ nanodots (Figure 14s). The p–p orbital coupling at the interface has been shown to promote efficient electron transfer from the electron-rich g-C₃N₄ to SnO₂, which optimizes the electronic structure of the active site (Figure 14t,u). This strategy effectively overcomes the selectivity limitations of conventional Sn-based catalysts through nanoconfined size tuning and interfacial electronic engineering, offering a novel paradigm for nanoconfined catalytic design.

4. Application and Analysis of Nanoconfined Catalysis in Various Catalytic Fields

Thermal catalysis drives high-temperature reactions (e.g., methane reforming, Fischer–Tröpsch synthesis) to achieve efficient conversion of carbon-based fuels and resource utilization of industrial exhaust gases. Electrocatalysis utilizes electrical energy to reduce CO₂ into high-value chemicals (e.g., CO, CH₃OH), coupling with renewable energy sources to enable a low-carbon cycle. Photocatalysis harnesses solar energy to excite charge carriers, directly splitting water to produce hydrogen or converting CO₂ into hydrocarbon fuels, offering green pathways for distributed clean energy systems. These three approaches, leveraging thermal, electrical, and solar energy inputs, respectively, synergistically advance efficient carbon resource utilization and carbon neutrality goals. Nanoconfinement catalysis has found applications across all three fields, and analysis of these applications is critical to deepen our understanding of the advantages of nanoconfinement.

4.1. Thermal Catalysis

The Wang team developed a novel Cu-ZnO@ZSM-5 core-shell catalyst, encapsulating Cu-ZnO nanoparticles within ZSM-5 zeolite layers via a steam-assisted crystallization method for efficient catalytic CO₂ hydrogenation to dimethyl ether (DME) and methanol [108]. Their study revealed that the spatial confinement effect of ZSM-5 effectively suppressed sintering and oxidation of the Cu-ZnO nanoparticles (Figure 15a–c). By optimizing the Cu/Zn molar ratio (0.9), Si/Al ratio (60), and crystallization time (24 h), the catalyst demonstrated exceptional performance at 260 °C and 5 MPa: CO₂ conversion reached 20.8%, total methanol/dimethoxy ethane selectivity attained 81.6% (with dimethoxy ethane accounting for 62.2%), and stable operation was maintained for 100 h (Figure 15d–g).

He et al. resolved the challenges of sintering-induced deactivation and insufficient metal exposure in traditional Ni-based catalysts under high-temperature conditions by constructing a dually confined microenvironment [51]. Dynamic sintering rate analysis revealed that Ni/S-SBA-15-OH exhibited an extremely low sintering rate of 0.7%/h (Figure 16a,b), significantly lower than other catalysts. Pyridine-IR demonstrated that Ni/S-SBA-15-OH possessed the highest number of Lewis acid sites, originating from electron transfer between Ni and the hydroxylated support (Figure 16c). In situ CH₄-DRIFTS and CH₄-temperature-programmed surface reaction mass spectrometry (TPSR-MS) confirmed the strongest CH₄ adsorption and activation capabilities of Ni/S-SBA-15-OH (Figure 16d–f). Additionally, the reaction pathway over Ni/S-SBA-15-OH featured an explicit *CHO intermediate (Figure 16g,h). Differential charge density and phononic density of states (PDOS) analyses revealed strong electronic interactions between Ni nanoparticles and the support, evidenced by hybridization of Ni d-orbitals with Si s/p-orbitals (Figure 16i,j).

4.2. Photocatalysis

Meng et al. [107] developed a novel Bi/TiO₂ photocatalyst by anchoring Bi clusters onto porous TiO₂ nanowires through alkali thermal synthesis, acid etching, high-temperature treatment, and wet impregnation (Figure 17a). The TiO₂ nanowires exhibited a 1D structure with an average mesopore diameter of 6.6 nm on the nanowire walls, while Bi clusters (~2.2 nm) were confined within the pores (Figure 17b,c). The specific surface area of Bi/TiO₂ (112.24 m²/g) surpassed that of pure TiO₂ (73.86 m²/g) (Figure 17d). The Bi/TiO₂ achieved 86.8% selectivity for CH₄, significantly higher than TiO₂ (46.2%), with a stable yield over five cycles, confirming structural robustness (Figure 17e,f). Electrochemical analysis revealed a smaller impedance arc radius for Bi/TiO₂, indicating faster charge transfer (Figure 17g). The significantly reduced photoluminescence intensity of Bi/TiO₂ suggested that Bi acted as an electron acceptor to suppress carrier recombination (Figure 17h). Bi/TiO₂ exhibited a higher photocurrent density, verifying the enhanced separation efficiency of the photogenerated electron-hole pairs (Figure 17i). XPS analysis demonstrated that under light, Ti 2p and O 1s peaks shifted to lower and higher binding energies, respectively, reflecting electron transfer from O to Ti. The Bi 4f peaks shifted to lower binding energies, indicating Bi participated as an electron donor during the reduction process (Figure 17j–l).

Li et al. [109] effectively regulated the product selectivity of CO₂ photoreduction by precisely controlling the spatial positions (within the core, at the interface, and on the shell surface) of PtCu alloy cocatalysts in the core-shell structured UiO-66@ZnIn₂S₄ (Figure 18a). The high specific surface area of UiO-66 dominated the adsorption performance of the composite. When PtCu was positioned closer to UiO-66 (PtCu/UiO/ZIS), the CO₂ adsorption capacity increased due to the unblocked pores of UiO-66 (Figure 18b). PtCu/UiO/ZIS primarily produced CO (52.1%) and H₂ (28.4%), UiO/PtCu/ZIS selectively generated CH₃OH (72.7%), and UiO/ZIS/PtCu mainly yielded CH₄ (88.8%). The O₂ production followed the order: PtCu/UiO/ZIS < UiO/PtCu/ZIS < UiO/ZIS/PtCu (Figure 18c,d). Experimental analysis revealed that the photocurrent density sequence—UiO/ZIS/PtCu > UiO/PtCu/ZIS > PtCu/UiO/ZIS—indicated that surface-anchored PtCu most effectively promoted charge separation, reflecting a positive correlation between product selectivity and charge separation efficiency (Figure 18e). The decreasing trend in PL intensity further supported the suppression of charge recombination (Figure 18f). Similarly, the gradual reduction in charge transfer resistance (R_ct) demonstrated that external PtCu placement lowered interfacial impedance and accelerated electron transport (Figure 18g).

4.3. Electrocatalysis

Mo et al. [52] developed a composite catalyst, Ru₃-SCs@Ni-PCN-222-PyrA, featuring Ni-PCN-222-PyrA-supported triruthenium single clusters (Ru₃-SCs) for efficient electrocatalytic CO₂ reduction to methane. Using a pre-coordination strategy, Ru₃(CO)₁₂ was encapsulated into the PyrA-modified Ni-PCN-222 channels, followed by microwave treatment to release CO and form Ru₃ single clusters (Figure 19a). The Ru₃ formed single clusters (≈0.8 nm, bright spots composed of three atoms) in Ru₃-SCs@Ni-PCN-222-PyrA, while Ru-SAs@Ni-PCN-222-PyrA exhibited isolated single-atom bright spots, providing a basis for subsequent performance comparisons (Figure 19b–e). LSV curves demonstrated that Ru₃-SCs@Ni-PCN-222-PyrA achieved a significantly higher current density (−68 mA∙cm⁻² at −1.5 V vs. RHE) than Ru-SAs@Ni-PCN-222-PyrA (Figure 19f). Additionally, Ru₃-SCs@Ni-PCN-222-PyrA exhibited superior CH₄ selectivity (71.8% at −1.0 V vs. RHE) compared to Ru-SAs@Ni-PCN-222-PyrA (16.8%) and Ni-PCN-222 (10.1%) under the same applied potential (Figure 19g,h). Simulations of the Gibbs free energy profiles showed that the energy barrier for *CO and *H coupling to form *CHO on Ru₃-SCs was significantly lower than that on Ru-SAs, confirming that the synergistic effect reduced the reaction difficulty (Figure 19i). After CO₂ adsorption on the active Ru₃-SCs, a series of proton-coupled electron transfer processes occurred, forming intermediates such as *COOH, *CO, *CHO, *CH₂O, and *CH₃O, ultimately yielding the final product, CH₄.

Wang et al. [110] investigated the regulatory mechanism of mesoporous SiO₂ shell-coated Cu₂O nanospheres for CO₂ electroreduction to multi-carbon products (C₂₊). The synthesis involved preparing Cu₂O cores and controlling the SiO₂ shell thickness via the Stöber method (Figure 20a). TEM and HAADF-STEM images revealed the core-shell structure of Cu₂O@MSS_15nm (Figure 20b,c). Atomic-resolution HAADF-STEM images confirmed the Cu₂O (111) crystal plane (0.246 nm lattice spacing) in the core region and the amorphous SiO₂ shell (no lattice fringes) (Figure 20d). Performance tests showed that OD-Cu@MSS_15nm achieved the highest C₂₊ Faradaic efficiency (FE) of 83.1% at −1.45 V vs. RHE (Figure 20e). A volcano-type relationship between C₂₊ FE and shell thickness was observed, with 15 nm thickness yielding optimal performance (Figure 20f). Compared to other catalysts, OD-Cu@MSS_15nm exhibited leading C₂₊ current density (687.8 mA cm⁻²) and FE (Figure 20g). Multiphysics simulations revealed that an increased shell thickness elevates the local OH⁻ concentration (suppressing HER) but reduces the CO₂ concentration, with these tradeoffs governing the volcano-type trend (Figure 20h–j).

5. Summary and Outlook

Nanoconfined catalysts enhance reaction efficiency, reduce energy consumption, and suppress byproduct emissions through precise regulation of active sites. By efficiently catalyzing carbon-based energy conversion and clean energy synthesis, they promote carbon cycling, mitigate greenhouse gas emissions, and provide critical technological support for green industries and climate governance. This paper focused on the application of nanoconfined catalytic technology in carbon-based energy conversion (e.g., CO₂ and CH₄ conversion), constructing a complete logical framework through progressive layers: background significance, classification mechanisms, optimization strategies, and application analysis. First, starting from the global energy transition and dual-carbon strategy, we emphasized the central role of greenhouse gas catalytic conversion technologies, discussing the performance of photo-/electro-/thermal catalysis versus emerging nanoconfined catalysis, highlighting the unique advantages of nanoconfined catalysis in modulating reaction pathways and enhancing selectivity and stability. Subsequently, under the theme of “confinement dimensions”, we systematically summarized four types of nanoconfined catalytic systems from the perspective of microstructural analysis and provided generalized conclusions. Next, we focused on three primary engineering tools for optimizing nanoconfined catalysts: heteroatom doping engineering to improve electrical conductivity and intermediate adsorption via electronic structure modification; defect engineering to lower reaction barriers through targeted construction of intrinsic defects; and surface modification to synergistically regulate local microenvironments via chemical modification and spatial confinement. Finally, we presented detailed analyses of nanoconfined catalysis applications across various catalytic fields. We believe research enthusiasm for nanoconfined catalytic materials will persist for an extended period. Therefore, we outline the challenges and prospects humanity faces in this field.

(I)

Although various structures have been developed to meet the demand for nanoconfined materials, creating nanoconfined materials that are easy to prepare, have excellent properties, exhibit structural stability, and can be applied in various environments remains a major challenge.

(II)

The coupled mechanisms of mass transfer, electronic effects, and interfacial chemistry in confined microenvironments have not been clarified, leading to difficulties in theoretical design.

(III)

Existing synthetic methods make it difficult to precisely control the size, shape and active site distribution of the confined cavity (e.g., uneven mass transfer due to the deviation of one-dimensional channel diameters), and the structure is prone to collapse at high temperature/pressure.

(IV)

Although the nanoconfined space can enrich reactants, the narrow channels tend to lead to increased mass transfer resistance (e.g., decreased CO₂ diffusion rate in 3D MOF pores), limiting the overall reaction rate.

(V)

Laboratory-scale nanoconfined catalysts are complicated to synthesize (e.g., growing a graphene cover layer by the CVD method) and have high precious metal dependence (e.g., Pt-based confined systems), which makes it challenging to meet the demand for scale-up applications.

(VI)

Existing studies have mainly focused on single gas (e.g., CO₂ or CH₄) conversion and are not sufficiently adapted to real industrial exhaust gases (with SO_x/NO_x impurities) or liquid reaction systems (e.g., biomass-derived liquids).

Future research strategies should focus on the following aspects to address the above challenges. (i) Constructing multi-scale computational models (DFT + machine learning) to quantify the effects of microenvironmental parameters (electric field strength, local pH) on reaction pathways. (ii) Designing model catalysts (e.g., single-atom arrays, bionic confined cavities) to isolate single variables and reveal key regulatory factors (e.g., the contribution of H₂O molecular arrangement in the confined space to HER inhibition). (iii) Integrating knowledge and methods from multiple disciplines, such as materials science, chemistry, physics, and computational science, to form a collaborative research mechanism to promote research progress on nanoconfined catalysis through interdisciplinary collaboration. (iv) Using advanced characterization techniques such as synchrotron radiation light sources, aberration-corrected transmission electron microscopy, and in situ characterization techniques to deeply reveal the microstructure and catalytic mechanism of nanoconfined catalysts and to provide accurate data support and theoretical guidance for research on nanoconfined catalysis.

Finally, we hope that this review will provide researchers with valuable insights into nanoconfined catalysis in carbon-based energy conversion, thereby promoting further advancements in related research on nanoconfined catalysis. Although we have summarized some of the applications of confined catalysis in carbon-based energy conversion in recent years, there is still a long way to go before it can be scaled up for industrial applications in the future. Nanoconfined catalytic technology needs to break through the three aspects of “precise structure, clear mechanism, and green process”, and through interdisciplinary synergy (material computation, in situ characterization, engineering thermodynamics) to achieve the leap from basic research to industrial implementation, and ultimately promote the construction of high-efficiency and low-carbon energy systems under the dual-carbon goal.