Editorial Catalysts: Catalytic Materials Enabling Sustainable Environmental Remediation and Clean Energy Conversion

Amid the escalating global imperatives for energy transition and environmental sustainability, advanced catalytic materials and technologies have emerged as a cornerstone in enabling a low-carbon, circular economy [1,2]. In response to the dual challenges of climate change and environmental degradation driven by fossil fuel dependence, the international scientific and industrial communities are intensifying efforts to develop green alternatives. Catalysis, renowned for its unparalleled efficiency, selectivity, and atom economy, plays an indispensable role across critical domains, including renewable energy conversion, environmental remediation, and the sustainable synthesis of high-value chemicals [3].

The design paradigm for catalytic materials is undergoing a transformative shift from empirical, trial-and-error approaches toward rational, mechanism-guided engineering. This evolution is underpinned by the synergistic integration of multidisciplinary advances in characterization, theory, and data science [4]. In particular, in situ and operando characterization techniques now enable real-time, atomic-scale observation of catalyst dynamics under working conditions, offering unprecedented mechanistic insights into active site evolution, reaction intermediates, and deactivation pathways. Complementarily, breakthroughs in computational catalysis, especially the widespread application of density functional theory (DFT) and the emerging integration of machine learning and artificial intelligence, empower researchers to predict catalytic activity, selectivity, and stability from first principles, thereby dramatically accelerating the discovery and optimization of next-generation materials [5,6]. Together, these tools constitute the foundation of “directed design”, steering catalysis research toward precision synthesis with atomic-level control.

Concurrently, the structural and electronic engineering of catalytic materials follows a clear trajectory: maximizing atom utilization efficiency while enabling fine-tuned modulation of electronic structure and local coordination environments. This has shifted the research focus from conventional nanoparticle catalysts toward the atomic-precision construction and regulation of active sites [7]. A prominent example is the development of integrated catalytic pairs (ICPs) adjacent, electronically coupled dual-active sites that synergistically facilitate multi-step reactions involving complex reaction networks, thereby transcending the intrinsic limitations of isolated single-atom or single-site catalysts [8]. Moreover, strategic manipulation of the catalyst microenvironment through coordination sphere engineering, defect engineering, and interface design allows for precise tuning of the electronic state, adsorption energetics, and steric environment of active centers, leading to marked enhancements in both intrinsic activity and long-term operational stability [9,10].

This Special Issue of Catalysts presents a curated collection of nine original contributions including seven research articles and two reviews that span advancements in clean energy conversion, advanced environmental remediation, and the rational design and multiscale characterization of next-generation catalytic materials. Collectively, these works underscore how atomic to mesoscale control over catalyst architecture, coupled with mechanistic elucidation under operando conditions, can address pressing challenges in global sustainability. Beyond advancing fundamental understanding of catalytic phenomena, this body of work charts a strategic roadmap for the development of scalable, high-performance technologies aligned with net-zero objectives.

The persistent threat posed by antibiotic and dye-laden wastewater continues to demand innovative catalytic solutions. In Contribution 1, Zhang et al. report the synthesis of cobalt-doped graphitic carbon nitride (Co g-C₃N₄) via one-step thermal polymerization. The strategic incorporation of Co atoms induces interlayer electronic coupling, establishing efficient pathways for charge transport that markedly enhance both spatial charge separation and reactive oxygen species (ROS) generation under visible irradiation. The optimized CoCN_0.02 catalyst achieves 97% degradation of tetracycline within 30 min, exhibiting exceptional activity and robustness even in complex real-water matrices. Complementing this inorganic approach, Contribution 4 by Zhou et al. introduces an organic–organic type-II heterojunction formed through electrostatic supramolecular assembly between perylene di-imide carboxylic acid (PDI–COOH) and its reduced counterpart (PDINH). This structure expands the π conjugation and promotes the vector separation of electrons and holes, thereby increasing the degradation efficiency of model organic pollutants by 67%, which is 1.7 times higher than that of the original PDINH material. This highlights the potential of metal-free organic photocatalysts in solar-driven environmental purification that has not yet been fully exploited.

In the realm of carbon-neutral fuel and chemical synthesis, CO₂ valorization and green hydrogen production stand as twin pillars of sustainable energy systems. Contribution 5 by Liu et al. details the development of rapidly quenched skeletal Cu (RQ Cu) catalysts via selective leaching of Cu–Al alloys. Notably, the RQ Cu-3 variant (treated with 3 wt% NaOH) retains a higher residual Al content, which effectively suppresses Cu nanoparticle sintering and stabilizes surface active sites. This catalyst delivers 13.7% CO₂ conversion with 97.9% methanol selectivity at 473 K, significantly outperforming conventional Cu/ZnO/Al₂O₃ benchmarks. Turning to hydrogen evolution, Contribution 7 by Jiang et al. engineers a one-dimensional tubular carbon nitride (TCN) support decorated with Ni₂P nanoparticles. The tubular morphology shortens bulk-to-surface carrier diffusion lengths, while Ni₂P functions as a highly active non-precious cocatalyst for proton adsorption and H–H coupling. The resulting 3 wt% Ni₂P/TCN composite achieves a remarkable H₂ evolution rate of 3715 μmol·h⁻¹·g⁻¹, rivaling Pt-based systems and maintaining stable performance over 16 h of continuous illumination. Pushing further into metal-free photocatalysis, Contribution 3 by Zhao et al. demonstrates a series of spirobifluorene-based donor–acceptor conjugated microporous polymers (CMPs). Through precise modulation of the donor/acceptor (D/A) ratio, the authors achieve an outstanding H₂ evolution rate of 22.4 mmol·h⁻¹·g⁻¹, illustrating how molecular-level engineering of electronic band structure and porosity in covalent organic frameworks can unlock exceptional photocatalytic efficiency without transition metals.

Finally, the catalytic upgrading of biomass-derived platform molecules offers a renewable route to high-value chemicals. In Contribution 2, Li et al. present a rationally designed Pt/WO_x-Al₂O₃ bifunctional catalyst for the selective hydrogenolysis of glycerol to 1,3-propanediol (1,3-PDO), which is a valuable monomer for polyesters. Systematic optimization reveals that a WO_x loading of 10 wt% maximizes the density of medium-strength Brønsted acid sites while preserving high Pt dispersion. This synergy between metal and acid functions enables a stable 43% selectivity to 1,3-PDO over 120 h on stream, setting a benchmark for long-duration performance in polyol upgrading. This study exemplifies how tailored bifunctionality at the nanoscale can steer complex reaction networks toward thermodynamically and kinetically challenging products.

Covalent organic frameworks (COFs) and metal organic frameworks (MOFs) represent two paradigmatic classes of crystalline porous materials whose precise structural tunability, tailorable active sites, and engineerable electronic landscapes render them uniquely suited for advanced catalytic applications. In Contribution 9, Meng et al. present a timely and comprehensive review on COF-based photocatalysts for the selective two-electron oxygen reduction reaction (2e⁻ ORR) toward H₂O₂ production. The author systematically expounded the key molecular design principles, including functional group engineering, donor-acceptor sequence integration, and spatial separation of oxidation and reduction centers. These principles collectively enabled certain covalent organic framework materials to achieve a H₂O₂ generation rate of over 7300 μmol·h⁻¹·g⁻¹ under visible light, while operating through a clean, metal-free process and with a very low overpotential requirement.

Complementing this, Contribution 6 by Wei et al. showcases the strategic potential of post-synthetic modification (PSM) in MOF catalysis. By covalently grafting acetylacetone (AA) onto the amino-functionalized Ti-MOF MIL-125-NH₂, the authors introduce oxygen vacancies and modulate the local coordination and electronic structure of Ti⁴⁺ centers. Intriguingly, photocatalytic activity follows a non-monotonic dependence on AA loading, with the optimally modified sample (MIL-125-AA-54%) delivering the highest singlet oxygen (¹O₂) quantum yield. This observation crystallizes a critical “defect dose principle”: catalytic performance is maximized not at maximal functionalization but at an optimal defect density that balances active site creation against structural integrity and charge transport efficiency.

To bridge the synthesis–performance gap, mechanistic insight grounded in advanced operando characterization is indispensable. In Contribution 8, Cui et al. provide a concise yet insightful mini-review on next-generation X-ray photoelectron spectroscopy (XPS) methodologies. They emphasize how emerging techniques, such as in situ irradiation XPS (ISI-XPS) and gentle sputter depth profiling with minimal beam damage, which enable direct and real-time tracking of surface redox states, interfacial electron transfer, and adsorbate–catalyst interactions under working conditions. Such capabilities are pivotal for establishing quantitative structure–activity relationships (QSARs) and moving beyond correlative to causal understanding in heterogeneous photocatalysis.

Collectively, the contributions assembled in this Special Issue illustrate the vibrant convergence of molecular precision, nanoscale engineering, and mechanistic rigor that defines modern catalysis research. Through sophisticated strategies, including defect engineering, heterojunction construction, morphological control, and post-synthetic functionalization, significant progress has been made in multiple key areas of sustainable development: environmental pollutant degradation, CO₂-to-fuel conversion, green hydrogen evolution, and the catalytic valorization of renewable feedstocks. Critically, these material innovations are increasingly informed and validated by advanced in situ/operando characterization, ensuring that design hypotheses are rooted in mechanistic reality.

Looking ahead, the field stands at an inflection point where the integration of high-throughput computational screening, machine learning guided discovery, and community-adopted standardized metrics (e.g., for solar-to-hydrogen efficiency or turnover frequency under comparable conditions) will be essential to accelerate the translation of laboratory breakthroughs into scalable technologies. We are confident that the foundational work presented herein will not only deepen fundamental understanding but also inspire the next generation of catalysts that are scientifically elegant, technologically viable, and environmentally transformative.

We extend our deepest gratitude to all authors, peer reviewers, and editorial staff for their exceptional contributions, rigorous insights, and unwavering commitment to scientific excellence. It is our sincere hope that this Special Issue will serve as both a benchmark and a catalyst, spurring further innovation toward a sustainable, low carbon future powered by intelligent catalytic design.