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Review

Rational Design Strategies for Covalent Organic Frameworks Toward Efficient Electrocatalytic Hydrogen Peroxide Production

by
Yingjie Zheng
†,
Yi Zhao
†,
Wen Luo
,
Yifan Zhang
,
Yong Wang
and
Yang Wu
*
Department of Chemical Engineering, School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai 200444, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Catalysts 2025, 15(5), 500; https://doi.org/10.3390/catal15050500
Submission received: 1 April 2025 / Revised: 16 May 2025 / Accepted: 19 May 2025 / Published: 21 May 2025
(This article belongs to the Special Issue Powering the Future: Advances of Catalysis in Batteries)
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Abstract

:
Hydrogen peroxide (H2O2) is a versatile and environmentally friendly oxidant with broad applications in industry, energy, and environmental remediation. Electrocatalytic H2O2 production via the two-electron oxygen reduction reaction (2e− ORR) has emerged as a sustainable alternative to traditional anthraquinone processes. Covalent organic frameworks (COFs), as a class of crystalline porous materials, exhibit high structural tunability, large surface areas, and chemical stability, making them promising electrocatalysts for 2e− ORR. This review systematically summarizes recent advances in COF-based electrocatalysts for H2O2 production, including both metal-free and metal-containing systems. We discuss key strategies in COF design—such as dimensional modulation, linkage engineering, heteroatom doping, and post-synthetic modification—and highlight their effects on activity, selectivity, and stability. Fundamental insights into the 2e− ORR mechanism and evaluation metrics are also provided. Finally, we offer perspectives on current challenges and future directions, emphasizing the integration of machine learning, conductivity enhancement, and scalable synthesis to advance COFs toward practical H2O2 electrosynthesis.

Graphical Abstract

1. Introduction

Hydrogen peroxide (H2O2) is a pivotal environmentally friendly oxidizing agent with widespread applications in chemical engineering, environmental remediation, healthcare, and energy sectors [1,2]. Its unique chemical properties and clean decomposition products (solely generating water and oxygen) exemplify the principles of green chemistry and sustainable development. H2O2, boasting an active oxygen content of 47.1%, enables advanced oxidation processes (AOPs) for efficient organic pollutant degradation through reactive oxygen species (ROS) generation [3]. Moreover, its exceptional bactericidal properties have established it as a critical disinfection reagent [4,5]. In recent years, H2O2 has garnered significant attention as a green energy carrier, with its decomposition releasing approximately 96 kJ·mol−1 of energy, potentially serving as a rocket propellant or novel mechanical fuel [6,7]. Unlike traditional energy storage systems, H2O2 can be stored without high-pressure or low-temperature requirements, thereby reducing system complexity and associated costs. As global interest in green chemistry continues to intensify, the multifaceted importance of H2O2 has become increasingly apparent, necessitating the development of more sustainable, efficient, and safe synthesis pathways [8,9].
Currently, industrial H2O2 production predominantly relies on the anthraquinone oxidation (AO) method, which has dominated since the 1940s. However, this process suffers from significant drawbacks, including high energy consumption, substantial byproduct generation, and considerable environmental burden [10,11,12]. The complex workflow requires extensive organic solvent recycling and is accompanied by heavy metal catalyst degradation and organic waste generation, resulting in prohibitive waste treatment costs and environmental risks [13]. An alternative approach involves the direct catalytic synthesis of H2O2 from hydrogen and oxygen. Despite its theoretical simplicity, this method remains challenging for industrial-scale implementation due to explosion risks, high dependence on metal catalysts (such as Pd, Pt), and insufficient activity selectivity [14,15]. Traditional processes typically rely on centralized large-scale production, introducing serious safety concerns in high-concentration H2O2 transportation and storage, further escalating costs and risks [12,13].
Consequently, developing a more green, safe, and decentralized H2O2 production technology has emerged as a critical research focus. Electrocatalytic H2O2 synthesis via the two-electron oxygen reduction reaction (2e− ORR) presents a promising alternative, characterized by mild operating conditions, compatibility with renewable energy, and on-site production capabilities [13,16]. This method not only demonstrates high energy efficiency through one-step H2O2 generation but also eliminates the use of organic solvents and high-pressure hydrogen, offering remarkable safety and environmental friendliness [17]. Moreover, electrocatalytic technology exhibits excellent economic feasibility and scalability, suitable for distributed small-scale production and reducing infrastructure investments, particularly advantageous for remote regions or on-site preparation requirements. Furthermore, this approach can be integrated into microbial fuel cells or dual-cathode systems, simultaneously generating electricity and degrading organic pollutants [13,16].
Covalent organic frameworks (COFs), a class of porous crystalline materials constructed through covalent bonds using light elements, demonstrate extraordinary potential in electrocatalysis [7,18,19,20,21]. Characterized by ordered channels, high specific surface areas, and structural designability, COFs offer unique advantages [5,22,23,24,25,26,27,28]. COFs exhibit great chemical stability in acidic, alkaline, and electrochemical environments, rendering them suitable for long-term catalytic reactions under harsh conditions [29,30]. The exceptional tunability of COFs provides extensive opportunities for electronic structure modulation, active site design, heteroatom doping, and functional group modifications, making them ideal platforms for constructing high-efficiency electrocatalysts [10,13,17]. Currently, COF-based materials have been widely applied in crucial reaction processes such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and CO2 reduction reaction (CO2RR), contributing to clean energy cycle systems and advancing carbon neutrality and environmental protection goals [7,31]. However, significant challenges persist in COF electrocatalytic applications, including low electrical conductivity limiting electron transfer efficiency, the structural instability of two-dimensional layered structures, difficulties in controlling active site distribution, and challenges in scale-up production and cost management [32,33,34,35].
This review systematically examines the latest research advances in COF materials for electrocatalytic H2O2 production. By analyzing the fundamental principles and critical evaluation metrics of 2e− ORR, the manuscript explores COF construction strategies, performance advantages, and current technological bottlenecks from a structural perspective. The review focuses on structural design and modulation approaches for COF electrocatalysts, including dimensional structure design, linkage engineering, heteroatom doping, electronic structure regulation, and composite strategies1. Finally, the review provides a forward-looking perspective on future research directions for COFs in this domain, such as precise active site design, machine learning-assisted material screening, high-conductivity COF development, and green co-production process integration, aiming to provide theoretical references and research pathways for continued advancement in the field. In preparing this review, we focused on peer-reviewed studies published primarily between 2018 and 2025 that reported the electrocatalytic performance of COFs for H2O2 production via the 2e− ORR. Both experimental and computational studies were included. The selection emphasized works that provided mechanistic insights, reported quantitative performance metrics such as Faradaic efficiency and H2O2 selectivity, and described structure–property relationships. Particular attention was given to studies that demonstrated novel COF topologies, heteroatom incorporation strategies, or post-synthetic modifications relevant to catalytic activity. Studies without performance data or clear structural design relevance were excluded.

2. Fundamental Principles and Evaluation of Electrocatalytic H2O2 Production

The oxygen reduction reaction (ORR) represents a complex electrochemical process occurring at the gas–liquid–solid three-phase interface, encompassing intricate steps of oxygen molecule adsorption, synergistic electron–proton transfer, and chemical bond transformations [15,36,37]. The reaction can be fundamentally categorized into two primary pathways (Figure 1a): the two-electron oxygen reduction reaction (2e− ORR) and the four-electron oxygen reduction reaction (4e− ORR), each characterized by distinct mechanisms and product formations. The 2e− ORR pathway predominantly generates hydrogen peroxide (H2O2), while the 4e− ORR pathway directly produces water (H2O) [38,39,40]. The critical mechanistic distinction lies in the treatment of the oxygen–oxygen bond. During 4e− ORR, the O2 molecule undergoes strong catalyst interactions, leading to O-O bond rupture and water generation. Conversely, in 2e− ORR, the O-O bond remains structurally intact, forming a peroxide intermediate that ultimately yields H2O2. Pathway selectivity is governed by the catalyst surface’s capacity to adsorb reaction intermediates and facilitate electron transfer kinetics [41]. Researchers have identified several adsorption configurations, including Pauling (end adsorption), Griffiths (bridge adsorption), and Yeager (side adsorption) configurations (Figure 1b) [40]. Empirical studies suggest that the Pauling configuration favors the 2e− ORR, whereas the Yeager configuration tends to promote the 4e− ORR. An optimal 2e− ORR catalyst should demonstrate high O2 molecule adsorption capacity coupled with weak peroxy radical (OOH*) adsorption, facilitating intermediate formation and product release. Theoretical computational approaches have revealed that the Gibbs free energy of OOH* intermediates (ΔGOOH*) serves as a crucial predictive parameter for catalyst performance. A high-efficiency 2e− ORR typically requires the ΔGOOH* value to approximate the volcano plot’s peak [42]. Characteristically, the 2e− ORR exhibits lower electrocatalytic activity but superior selectivity, while the 4e− ORR demonstrates opposite traits. Consequently, developing effective H2O2 electrosynthesis catalysts necessitates a delicate balance between activity and selectivity [43,44].
Comprehensive electrocatalyst evaluation requires a systematic assessment framework addressing multiple performance dimensions. Key metrics include catalytic activity, selectivity, Faradaic efficiency, energy efficiency, and stability [45,46]. Catalytic activity is typically characterized through current density, which reflects the catalyst’s ability to generate H2O2 at low overpotentials. Overpotential measurements provide insights into the additional energy required for the catalytic reaction, with lower values indicating enhanced energy efficiency. Selectivity emerges as a decisive indicator in electrocatalytic H2O2 production, quantifying the catalyst’s ability to preferentially guide oxygen reduction toward the 2e− ORR pathway. The Rotating Ring–Disk Electrode (RRDE) method has become the standard technique for precise selectivity measurements, offering real-time monitoring of product formation and pathway preferences [47,48]. Faradaic efficiency complements selectivity by quantifying the ratio of electrons consumed in H2O2 generation relative to total electron transfer [40,41]. This metric provides a nuanced understanding of electrical energy utilization efficiency, bridging theoretical potential with practical performance. Catalyst stability represents a critical parameter for practical applications, particularly in long-term industrial operations. Evaluation methodologies involve extended electrolysis testing, monitoring current density and potential changes to assess degradation mechanisms and performance durability [31]. Future research directions for electrocatalytic H2O2 production focus on molecular design strategies, electrical conductivity improvements, and stability enhancement. For COF-based catalysts, addressing inherent conductivity limitations while maintaining high selectivity remains a paramount research challenge [6,49,50].

3. Structural Basis and Design Principles of COFs for Electrocatalytic H2O2 Production

3.1. Fundamental Features of COFs

COFs are ordered porous crystalline materials constructed by light elements (such as C, H, B, N, and O) through covalent bonds [5,32,33,51,52,53]. COFs exhibit great chemical stability, high specific surface area, and flexible structural design capabilities [28,35,54,55,56].
One of their most distinguishing characteristics compared to other organic polymers is their high crystallinity, which ensures both performance stability and reproducibility [57,58,59,60]. This crystallinity largely stems from the reversible formation of covalent bonds during synthesis, which allows the framework to undergo self-healing and eliminate structural defects, ultimately resulting in highly ordered architectures. High crystallinity in COFs offers multiple advantages for electrocatalytic H2O2 production. First, it ensures a uniform and well-defined distribution of active sites, enabling consistent reaction pathways and enhanced selectivity toward the 2e− ORR [10]. Second, the ordered frameworks facilitate charge transport by supporting extended π-conjugation and promoting efficient electron delocalization throughout the backbone [7]. This structural regularity reduces energy barriers for electron transfer, resulting in higher Faradaic efficiency and catalytic activity. Furthermore, high crystallinity enhances the long-term operational stability of COFs by minimizing structural collapse or degradation during electrolysis. Collectively, these attributes make highly crystalline COFs excellent platforms for studying structure–activity relationships and for designing robust, high-efficiency electrocatalysts [18,61].
Pore structure is another defining feature of COFs and plays a critical role in determining their electrocatalytic performance. Pore size directly influences the diffusion rates and mass transport pathways of reactants, intermediates, and products. Tuning the pore size enables improvements in O2 adsorption, proton transfer, and H2O2 release efficiency. Larger pores promote mass transport, reduce diffusion resistance, and improve the accessibility of oxygen, thereby enhancing both the H2O2 production rate and Faradaic efficiency [20]. Furthermore, the integration of hierarchical pore architectures—combining micropores, mesopores, and macropores—can synergistically enhance mass transfer and catalytic site utilization [62]. Macropores and mesopores act as efficient diffusion channels for oxygen and electrolytes, while micropores provide a dense distribution of active sites. This hierarchical porosity is especially advantageous for establishing efficient gas–liquid–solid triple-phase interfaces, significantly boosting both the selectivity and productivity of H2O2 electrosynthesis [63,64].

3.2. Design Principles of COFs for Electrocatalytic H2O2 Production

A core advantage of COF materials lies in their highly predesignable nature, allowing for broad structural freedom through the selection of monomers, linkage types, and topologies (Figure 2) [65,66]. In addition, their post-synthetic modifiability further enhances structural versatility [67]. This section explores four structural strategies that regulate electrocatalytic performance: dimensional modulation, linkage engineering, heteroatom doping, and post-synthetic modification, with each approach influencing activity, selectivity, and stability.

3.2.1. Dimensional Modulation

Dimensional modulation significantly affects the transport and accessibility of reactive species. The dimensionality of COFs—ranging from 1D chains to 2D sheets and 3D networks—plays a central role in their electrocatalytic behavior [34,68,69,70]. One-dimensional COFs, often fibrous or tubular, facilitate directional electron transport and provide unique interface characteristics. For example, PYTA-TPEDH-COF, a 1D framework incorporating rigid π-units, exhibited excellent H2O2 selectivity (85.8–82.0%), significantly outperforming its 2D analog PYTA-TPETH-COF (72.9–69.0%), indicating the advantage of edge-exposed active sites in 1D structures [70]. In contrast, two-dimensional COFs—currently the most extensively studied configuration—consist of planar layers connected via covalent bonds. These structures support efficient π–π stacking and in-plane electron delocalization, facilitating improved charge transport during catalysis. Three-dimensional COFs introduce spatial cross-linking to form interconnected networks, increasing specific surface area and pore volume. For example, the STP-topology-based 3D COF JUC-564 developed by Li et al. features a pore size of up to 43 Å and a surface area of 3300 m2·g−1, among the largest and lowest-density COFs reported to date, which significantly improves mass transport [71]. The high porosity of 3D COFs provides numerous accessible active sites, enhances reactant diffusion, and promotes efficient H2O2 generation and desorption, thereby improving both activity and stability. However, the structural complexity and insulating linkers in 3D COFs can lead to lower conductivity. To address this, Wang et al. developed BUCT-COF-7, a fully π-conjugated 3D COF synthesized via a one-pot Debus–Radziszewski reaction, achieving high H2O2 selectivity (83.4%) with improved mass and charge transport. Dimensionality also affects catalytic durability. While layered 2D COFs are prone to interlayer dissociation under long-term electrolysis, 3D frameworks exhibit higher rigidity and structural integrity under harsh conditions. Recently, a hybrid “2D/3D interwoven” strategy has emerged. For example, an unsaturated 2D-inserted 3D TAE-COF was developed by Wu et al., improving both electron mobility and active site utilization, and achieving high H2O2 selectivity and productivity under neutral conditions [72]. In summary, dimensional modulation affects pore accessibility, electron pathways, and reaction kinetics. Rational dimensional control, coupled with functional molecular design, provides essential guidance for constructing efficient and stable COF-based electrocatalysts for H2O2 production.

3.2.2. Linkage Engineering

In molecular design, COF materials can be constructed through various linkage types (Figure 3), including boron–oxygen bonds, boronic ester bonds, imine bonds, hydrazone bonds, and azole bonds. These linkages are critical not only in forming the backbone of the COF framework but also in determining its electronic structure, charge transport ability, porosity, and active site accessibility. Consequently, the linkage chemistry plays a key role in modulating the ORR pathway and the efficiency of H2O2 production [73,74,75]. For instance, hydrazone and azole linkages can introduce electron-donating or electron-withdrawing groups that fine-tune the local electronic environment around active centers, influencing the adsorption energy of key intermediates and thus affecting both selectivity and catalytic efficiency [76,77]. In a systematic study, Huang et al. [73] investigated the role of linkage types in the 2e− ORR pathway by synthesizing two COFs: imine-linked Py-TD-COF and amine-linked Py-TD-COF-NH. The imine-linked variant achieved significantly higher H2O2 selectivity (80–92%) compared to the amine-linked counterpart (50–61%). Both experimental data and DFT calculations showed that imine linkages facilitate donor–acceptor interactions, leading to appropriate O2 activation and high 2e− selectivity. In contrast, the amine linkage over-activated O2 due to altered electronic properties, causing a shift toward the 4e− ORR pathway and reduced selectivity. These findings highlight that precise control over linkage chemistry enables optimization of the framework’s electronic properties, and thus, its electrocatalytic performance. Therefore, by strategically selecting linkages and monomer units, COFs can be tailored to achieve optimal crystallinity, conductivity, and chemical stability—critical for high-performance H2O2 electrocatalysts.

3.2.3. Heteroatom Doping

Heteroatom doping is widely employed as an effective strategy to enhance the catalytic activity and selectivity of COFs for electrocatalytic H2O2 production. Introducing heteroatoms such as nitrogen (N), sulfur (S), phosphorus (P), or fluorine (F) into the framework can significantly alter the electronic structure and surface polarity of the COF. These dopants redistribute local charge density within the carbon framework, creating active centers that promote O2 adsorption and selective activation along the 2e− ORR pathway. For example, nitrogen doping introduces Lewis basic sites that facilitate O2 adsorption and activation, while boron, due to its electron-deficient nature, can stabilize the OOH* intermediate during the H2O2 formation process, lowering the overall energy barrier. Yang et al. designed a series of heterocyclic COFs with nitrogen-rich motifs, achieving over 95% H2O2 selectivity in mildly alkaline media by tuning the band structure of the material [78]. Similarly, Wu et al. synthesized sulfur-rich COFs from tetrazole-based monomers, which modulated O2 adsorption energies and improved the long-term electrochemical stability of the framework [79]. Co-doping strategies, such as simultaneous nitrogen and sulfur incorporation, have also been shown to enhance O2 activation and stabilize the 2e− ORR pathway. These results demonstrate that heteroatom doping not only optimizes the electronic microenvironment of COFs but also contributes to enhanced catalytic selectivity, durability, and corrosion resistance, thereby expanding the potential of COFs for green H2O2 electrosynthesis.

3.2.4. Post-Synthetic Modification

Beyond their inherent design flexibility, COFs also offer considerable post-synthetic modifiability [80,81,82,83,84,85,86,87,88], which further broadens their application scope [89]. Due to the presence of functional groups such as amines, aldehydes, hydroxyls, or carboxyls within the framework, COFs can undergo post-synthetic modification (PSM) without compromising crystallinity or porosity. This allows for the targeted introduction of functional groups, redox-active centers, or metal complexes, thereby enabling precise tuning of catalytic properties after the framework has been assembled (Figure 4). Post-synthetic modifications can serve multiple purposes: introducing electron-withdrawing or donating groups to modulate the charge density around active sites, adjusting the hydrophilic/hydrophobic character to enhance mass transport and product desorption, or anchoring catalytically active species such as metal ions or organic radicals. In the context of electrocatalytic H2O2 production, PSM enables fine control over the electronic environment, thereby enhancing selectivity toward the 2e− pathway [17]. Wu et al. applied metalation strategies to load transition metals like Co and Fe onto COF backbones [90]. The d-orbital structure of these metals was found to adjust OOH* adsorption energy, redirecting the ORR mechanism and improving both efficiency and selectivity. PSM can also enhance COF stability, particularly under harsh electrochemical conditions. For example, the conversion of traditional imine linkages to more robust amide bonds through PSM has been shown to significantly improve framework durability. Jiménez-Duro et al. reported a COF converted from imine to amide linkage that achieved 98.5% H2O2 selectivity and a turnover frequency (TOF) of 0.155 s−1—among the highest recorded for metal-free COF-based catalysts [91]. Furthermore, the mild conditions required for these modifications make PSM compatible with functional groups that would otherwise be degraded during direct synthesis. Overall, PSM decouples structural assembly from functional tuning, offering researchers unprecedented freedom in designing COFs with tailored performance for targeted electrochemical applications.
In conclusion, COFs offer a structurally tunable platform for electrocatalyst design, where dimensionality, linkage chemistry, heteroatom doping, and post-synthetic modifications can be precisely engineered to influence electrocatalytic performance. For instance, two-dimensional layered COFs enable efficient in-plane charge transport and π–π stacking, facilitating improved electron mobility during the 2e− ORR pathway. Three-dimensional COFs enhance mass transport and active site accessibility through interconnected pore networks, while one-dimensional structures promote edge-exposed active centers that favor OOH* adsorption. Moreover, specific linkages (e.g., imines) and heteroatom dopants (e.g., N, F) can modulate the electronic density around active sites, directly impacting H2O2 selectivity and reaction kinetics. These structure–performance relationships underline the importance of rational COF design tailored for electrocatalytic H2O2 production. A clear mechanistic understanding of how each structural element affects reactivity and selectivity will enable the development of next-generation COF-based electrocatalysts with enhanced efficiency, selectivity, and operational durability.

4. Typical COF Electrocatalytic Systems and Practical Cases

4.1. Metal-Free COF Catalysts

Metal-free COFs have garnered increasing attention as promising electrocatalysts for H2O2 synthesis via the 2e− ORR. Their tunable structural features, high crystallinity, and abundant heteroatom incorporation provide unique opportunities for optimizing activity, selectivity, and operational stability. This section discusses representative examples of metal-free COFs, categorized according to structural modulation strategies.
The type of linkage connecting the organic building blocks in COFs significantly influences their electronic structures, charge transport, and ability to stabilize ORR intermediates. In a comparative study, Huang et al. designed two structurally similar COFs with different linkages (Figure 5a)—Py-TD-COF (imine-linked) and Py-TD-COF-NH (amine-linked) [73]. The imine-linked Py-TD-COF achieved H2O2 selectivity as high as 92% due to the favorable electron delocalization and donor–acceptor interactions enabled by the imine bond, which stabilize the OOH* intermediate without over-activating O2. In contrast, the amine-linked variant suffered from excessive O2 activation, which promoted the undesired 4e− ORR pathway and reduced H2O2 selectivity to 50–61%. Fu et al. further expanded this approach by transforming imine linkages into more conjugated quinoline structures using Rh-catalyzed C–H activation (Figure 5b) [92]. This transformation improved π-electron delocalization and redistributed internal charges across the framework. As a result, the modified COF showed enhanced O2 binding and improved Faradaic efficiency for H2O2 production. Notably, the improved selectivity was attributed to a better balance between adsorption strength and desorption kinetics for the OOH* intermediate. These findings collectively demonstrate that the chemical nature and electronic character of the linkage play a vital role in modulating the energy landscape of the ORR, offering a powerful handle to boost both activity and selectivity in metal-free COFs.
Substituent groups on linker moieties serve as electronic modifiers that can subtly tune the local charge distribution, thereby influencing adsorption energies and catalytic performance. Li et al. synthesized a family of COFs (Figure 6a) by altering substituents on phenyl rings within the linker structure [93]. Among the tested variants, Br-substituted COF achieved the highest H2O2 selectivity (86.2%) due to its optimal electron-withdrawing strength, which modulated the adsorption energy of the O2 molecule and stabilized the reaction intermediate without inducing overbinding. The study revealed a non-linear relationship between substituent electronic character and catalytic performance: both strongly electron-donating (–OCH3) and strongly withdrawing (–NO2) groups detrimentally impacted selectivity. This suggests that achieving a moderate electron density at the catalytic site is essential for favoring the 2e− ORR pathway while suppressing deeper O–O bond cleavage. This principle can be extended to guide the rational design of linkers for tailored electronic environments. Wang and co-workers [94] reported the development of JUC-660 (Figure 6b), a benzyl-functionalized ionic COF bearing quaternary ammonium (QA) groups, which represents the first ionic COF employed for H2O2 electrosynthesis. The introduction of QA moieties reduced the adsorption energy of the OOH* intermediate, thereby steering the ORR from the 4e− to the desirable 2e− ORR pathway. Remarkably, in a flow cell configuration, JUC-660 achieved a sustained H2O2 production rate of over 1200 mmol·g−1·h−1 for more than 85 h with excellent Faradaic efficiency. This work underscores the utility of ionic functionalization in tuning the reaction energetics and selectivity of COF-based catalysts.
Heteroatom doping is an effective strategy to generate active sites and modulate the local electronic environment of COFs. Huang et al. incorporated thiazole and thiophene building blocks into COF backbones (Figure 6c), leveraging their intrinsic electron-rich character to promote O2 adsorption and activation [61]. The resulting frameworks exhibited improved H2O2 selectivity and enhanced structural durability, which the authors attributed to better charge delocalization and a higher density of catalytic sites. In another approach, Martínez-Fernández et al. developed fluorinated COFs with high crystallinity and hydrophobicity [16]. Fluorine atoms induced local dipoles and altered the electrostatic potential of the framework, thereby stabilizing the OOH* intermediate. These COFs achieved a turnover frequency (TOF) of up to 0.0757 s−1—among the highest values reported for metal-free COFs—highlighting the dual function of F-doping in enhancing both catalytic efficiency and chemical stability. These examples show that doping offers a flexible and powerful way to design active COFs with tailored surface polarity, binding affinity, and long-term durability—traits essential for practical H2O2 electrosynthesis.
The dimensional architecture of COFs plays a critical role in regulating active site exposure, mass transport, and electronic conduction. Zhang et al. reported BUCT-COF-7 (Figure 7a), a 3D imidazole-linked COF with extended π-conjugation [95]. Its 3D framework enabled interconnected pore channels and efficient charge mobility, achieving an H2O2 selectivity of 83.4% and outstanding durability under continuous electrolysis. In comparison, PYTA-TPEDH-COF (Figure 7b), a 1D framework containing rigid π-units, showed even higher selectivity (85.8%) than its 2D analog, PYTA-TPETH-COF (72.9%) [70]. The performance enhancement was attributed to improved exposure of active edge sites and more directional electron flow along the molecular chains. Interestingly, hybrid dimensional architectures such as TAE-COF (Figure 7c) have emerged to leverage the best of both worlds—planar conductivity and spatial mass transport [72]. Such frameworks show promise for future COF designs targeting industrial-level H2O2 production.
The examples presented in this section highlight how rational structural tuning of metal-free COFs can drastically influence their catalytic performance in the 2e− ORR. From linkage chemistry and electronic substituent tuning to heteroatom doping and dimensional design, each strategy provides a distinct lever to modulate adsorption energy, electron transfer, and stability. More importantly, these strategies are not mutually exclusive and may act synergistically when combined. Thus, integrating multiple design principles into a unified COF architecture could offer a powerful approach to developing next-generation electrocatalysts with high selectivity, scalability, and operational robustness for sustainable H2O2 electrosynthesis.

4.2. Metal-Based COF Catalysts

COFs incorporating metal centers have emerged as highly promising electrocatalysts for H2O2 synthesis via the 2e− ORR. Compared to metal-free analogs, metal-containing COFs offer tunable electronic environments and catalytic specificity through precisely engineered coordination sites. This section discusses recent representative studies focusing on different strategies to incorporate metal centers into COFs and the corresponding structure–activity relationships that govern their performance.
Single-atom catalysts (SACs) embedded in COF frameworks offer a unique opportunity to maximize atomic utilization and ensure uniform active site distribution. Huang et al. developed a series of Py-Bpy-COF-M systems (Figure 8a), where bipyridine ligands within the COF backbone chelate various metal ions (Mn, Fe, Co, Ni, Cu, Zn) [96]. Among these, the Zn-loaded Py-Bpy-COF showed the highest H2O2 selectivity (up to 99.1%), which was attributed to a high OOH* dissociation barrier that favors the 2e− pathway. The well-defined metal–N coordination environment enabled clear structure–performance correlations, and the catalyst demonstrated high stability when used in a flow cell Zn–air battery configuration. Similarly, Liu et al. constructed metal–N2 coordination sites within the interlayers of a dioxin-linked COF-318 by incorporating different metal ions (Figure 8b) [97]. Among the tested metals, the Ca–N2 site outperformed others, achieving over 95% H2O2 selectivity and a turnover frequency (TOF) of 11.63 s−1 per site—significantly surpassing the performance of Co and Ni counterparts. DFT calculations confirmed that Ca sites offered more favorable OOH* desorption energy, underpinning their enhanced selectivity. To systematically assess the catalytic potential of different transition metal centers in COFs, Liu et al. developed a set of porphyrin-based COF-366-M (Figure 8c) catalysts incorporating six 3d transition metals (Mn, Fe, Co, Ni, Cu, Zn) [98]. Experimental and theoretical studies revealed a pH-independent activity trend with Co–N4 sites delivering the highest intrinsic activity for 2e− ORR. The descriptor EO2*–EHOOH* (binding energy difference between O2 and H2O2 intermediates) effectively predicted performance, offering mechanistic insights for rational metal center selection in M–N–C architectures. This study established key structure–activity relationships and a predictive framework for transition metal centers in COF catalysts.
Yang et al. advanced the concept of electronic tuning through dynamic coordination environments by designing Pt single-atom sites in TP-TTA-COF (Figure 9a) [99]. The initial Pt–N1O1Cl4 site evolved in situ into Pt–N1O1(OH)2 during catalysis, as confirmed via X-ray absorption spectroscopy. This evolution enhanced OOH* formation and thus improved H2O2 selectivity up to 90% under alkaline conditions. Their findings emphasized the role of local coordination changes in tailoring catalytic behavior. Zhi et al. introduced a 2D dithiine-linked Co-phthalocyanine COF (CoPc-S-COF) with undulated layered architecture (Figure 9b) [100]. The incorporation of large sulfur atoms (C–S–C bridges) led to layer bending, which effectively exposed more Co centers and enhanced O2 accessibility. Compared to its planar analog CoPc-O-COF, the undulated CoPc-S-COF achieved superior H2O2 selectivity (>95%) and a high production rate (0.48 wt.% at 125 mA cm−2) due to both structural and electronic advantages. Guo et al. [101] developed a magnesium-porphyrin-based COF (MgP-DHTA-COF), in which Mg2+ ions were precisely anchored via pyrrolic N sites within a highly crystalline layered structure (Figure 9c). Compared with its metal-free analogue, the Mg-containing COF displayed superior activity and selectivity, achieving a Faradaic efficiency of 91% and H2O2 selectivity of 96% in alkaline media. Both experimental and computational results confirmed that the Mg–N coordination enhances OOH* adsorption and promotes 2e− ORR. This work highlights the catalytic potential of non-transition metals in COFs and underscores the importance of precise site engineering through heteroatom anchoring.
Metal-containing COFs provide a structurally defined and tunable platform to optimize H2O2 electrosynthesis. Key design principles include precise control over metal coordination environments, strategic ligand selection for electronic modulation, and topological innovations to enhance site exposure. These insights form a mechanistic basis for the rational design of next-generation COF-based electrocatalysts capable of combining high selectivity, efficiency, and long-term durability in green H2O2 production.

5. Conclusions and Future Perspectives

COFs have emerged as a structurally versatile and chemically stable class of porous crystalline materials with significant potential in electrocatalytic H2O2 production via the 2e− ORR (Table 1, Figure 10). Over the past decade, substantial progress has been achieved in synthesizing COFs with enhanced activity, selectivity, and stability. Structural strategies—such as dimensional modulation, linkage engineering, heteroatom doping, and post-synthetic modifications—have collectively broadened the scope of COF design. However, despite the diversity of approaches, a unified and predictive framework that links structural parameters to catalytic performance remains underdeveloped.
One of the most urgent tasks is to establish a clear structure–function relationship that can guide the rational design of next-generation COF catalysts. Dimensionality, for instance, plays a pivotal role in regulating mass transport, active site exposure, and electronic conductivity. One-dimensional COFs provide enhanced edge site accessibility, two-dimensional frameworks benefit from extended π-conjugation, and three-dimensional COFs offer interconnected diffusion channels and greater structural robustness. Nonetheless, the trade-offs between surface accessibility and charge mobility across dimensions are not yet fully understood. Future studies must quantitatively address how dimensionality affects the adsorption free energy of reaction intermediates—particularly the OOH* species—and in turn influences 2e− ORR selectivity.
In this context, several fundamental questions arise that warrant systematic exploration: What are the optimal dimensional configurations (e.g., 1D vs. 2D vs. 3D or hybrid architectures) that strike the best balance between electron transport and catalytic site utilization? How does pore architecture (pore size, shape, and hierarchy) govern oxygen accessibility and intermediate diffusion in the COF framework? How do different linkages and heteroatom dopants alter the local electronic environment and modulate the O2 activation pathway? Can we define reliable electronic or thermodynamic descriptors that directly correlate with H2O2 selectivity and Faradaic efficiency?
To answer these questions, the application of advanced in situ and operando characterization techniques is indispensable. Methods such as in situ X-ray absorption spectroscopy (XAS), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS) allow for real-time tracking of bond evolution, electronic structure changes, and reaction intermediate dynamics during catalysis. These techniques provide direct insights into the active site environment, enabling the correlation of structural transitions with catalytic behavior. The integration of time-resolved and environment-sensitive probes will be particularly crucial in understanding the dynamic restructuring of COF frameworks under working conditions.
Alongside experimental tools, data-driven methods—especially those powered by machine learning (ML) and high-throughput computational screening—represent a promising frontier. We propose the development of predictive ML models trained on structural descriptors such as ΔGOOH*, pore diameter, surface polarity, charge density, and coordination environment. These models should be complemented by large, curated datasets derived from both DFT calculations and experimental measurements, enabling the efficient prediction and discovery of high-performance COFs.
Additionally, the issue of poor intrinsic conductivity in COFs remains a bottleneck for practical application. Future efforts should focus on constructing fully conjugated frameworks, incorporating redox-active backbones, or hybridizing COFs with conductive substrates (e.g., graphene, carbon nanotubes). These modifications must be pursued in parallel with efforts to enhance mechanical stability and chemical robustness under continuous electrolysis conditions.
From a process engineering perspective, translating COF-based systems into scalable H2O2 production platforms will require the integration of COFs into flow cell configurations, the development of green synthesis routes, and the realization of continuous electrocatalytic operation. Co-production processes that combine H2O2 generation with other electrochemical functions (e.g., organic pollutant degradation or energy storage) may further improve system utility and economic feasibility.
In conclusion, COFs represent a highly promising but still evolving platform for sustainable H2O2 electrosynthesis. By combining structural precision, real-time mechanistic understanding, machine learning-based screening, and process integration, future research can unlock the full catalytic potential of COFs and contribute to scalable, selective, and energy-efficient chemical manufacturing.

Author Contributions

The project was conceived and supervised by Y.Z. (Yifan Zhang), W.L., Y.W. (Yong Wang) and Y.W. (Yang Wu). Manuscript writing and revisions were managed by Y.Z. (Yingjie Zheng), Y.Z. (Yi Zhao), Y.W. (Yong Wang) and Y.W. (Yang Wu). All authors contributed to the discussion of results and the development of manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Shanghai Pujiang Programme (23PJD037).

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (a) Illustration of the proposed ORR process. (b) Schematics of three types of structures of O2 adsorption on catalyst surface.
Figure 1. (a) Illustration of the proposed ORR process. (b) Schematics of three types of structures of O2 adsorption on catalyst surface.
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Figure 2. Basic topological diagrams for the design of COFs [18].
Figure 2. Basic topological diagrams for the design of COFs [18].
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Figure 3. Common types of linkages used to build COFs [5].
Figure 3. Common types of linkages used to build COFs [5].
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Figure 4. Common types of post-synthetic modification reactions used to functionalize COFs (triazole [80], ester [81], amide [82], amidoxime [83], thioether [84], thiocarbamate [85], coordination [86,87], oxidization [88]).
Figure 4. Common types of post-synthetic modification reactions used to functionalize COFs (triazole [80], ester [81], amide [82], amidoxime [83], thioether [84], thiocarbamate [85], coordination [86,87], oxidization [88]).
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Figure 5. (a) The chemical structures of Py-TD-COF, Py-TD-COF-NH, and the schematic illustration of their electrocatalytic 2e− ORR [73]. (b) Schematic representation for the synthesis of NQ-COFTAPPy-TzDA using PSM and OPR methods, and top views of the eclipsed stacking of I-COFTAPPy-TzDA (left) and NQ-COFTAPPy-TzDA (right) [92].
Figure 5. (a) The chemical structures of Py-TD-COF, Py-TD-COF-NH, and the schematic illustration of their electrocatalytic 2e− ORR [73]. (b) Schematic representation for the synthesis of NQ-COFTAPPy-TzDA using PSM and OPR methods, and top views of the eclipsed stacking of I-COFTAPPy-TzDA (left) and NQ-COFTAPPy-TzDA (right) [92].
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Figure 6. (a) Constructing COFs for 2e− ORR via linker engineering [93]. (b) Synthesis and structures of JUC-658, JUC-659, and JUC-660 [94]. (c) Illustration of COF electrocatalysts studied in this work with activity dependence for the potential-limiting step, and the adjustment of the 2e− ORR activity of different COFs by tailoring the electronic structure of active sites with by-design building blocks [61].
Figure 6. (a) Constructing COFs for 2e− ORR via linker engineering [93]. (b) Synthesis and structures of JUC-658, JUC-659, and JUC-660 [94]. (c) Illustration of COF electrocatalysts studied in this work with activity dependence for the potential-limiting step, and the adjustment of the 2e− ORR activity of different COFs by tailoring the electronic structure of active sites with by-design building blocks [61].
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Figure 7. (a) The synthetic route and a space-filling model viewed along the c-axis of imidazole-linked fully conjugated 3D BUCT-COF-7 [95]. (b) Synthesis of 1D TPETA-TPEDH-COF and PYTA-TPEDH-COF from TPETA, TPEDH, and PYTA by solvothermal methods [70]. (c) The model compounds of 2D ET-COF and 3D TA-COF, the 2D/3D framework interlaced crystal ETT-COF, TAE-COF, and the amorphous TAET-COP [72].
Figure 7. (a) The synthetic route and a space-filling model viewed along the c-axis of imidazole-linked fully conjugated 3D BUCT-COF-7 [95]. (b) Synthesis of 1D TPETA-TPEDH-COF and PYTA-TPEDH-COF from TPETA, TPEDH, and PYTA by solvothermal methods [70]. (c) The model compounds of 2D ET-COF and 3D TA-COF, the 2D/3D framework interlaced crystal ETT-COF, TAE-COF, and the amorphous TAET-COP [72].
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Figure 8. (a) Schematic illustration of the synthesis process of Py-Bpy-COF and Py-Bpy-COF-Zn [96]. (b) Synthesis and chemical structure COF-318 and M-COF-318 [97]. (c) Schematic illustration of the synthesis of COF-366-M [98].
Figure 8. (a) Schematic illustration of the synthesis process of Py-Bpy-COF and Py-Bpy-COF-Zn [96]. (b) Synthesis and chemical structure COF-318 and M-COF-318 [97]. (c) Schematic illustration of the synthesis of COF-366-M [98].
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Figure 9. (a) Schematic of PtCl–COF synthesis and evolution tracking of atomic sites [99]. (b) The synthesis route of CoPc-O-COF and CoPc-S-COF [100]. (c) Schematics of the solvothermal synthesis of MP-DHTA-COF from MP (H2P or MgP) and DHTA building units, the electrochemical synthesis of H2O2 over MgP-DHTA-COF, and the atomic configuration of OOH* adsorption on H2P and MgP [101].
Figure 9. (a) Schematic of PtCl–COF synthesis and evolution tracking of atomic sites [99]. (b) The synthesis route of CoPc-O-COF and CoPc-S-COF [100]. (c) Schematics of the solvothermal synthesis of MP-DHTA-COF from MP (H2P or MgP) and DHTA building units, the electrochemical synthesis of H2O2 over MgP-DHTA-COF, and the atomic configuration of OOH* adsorption on H2P and MgP [101].
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Figure 10. Timeline on the developments of COFs for electrocatalytic H2O2 production.
Figure 10. Timeline on the developments of COFs for electrocatalytic H2O2 production.
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Table 1. Typical COFs as electrocatalysts for electrocatalytic hydrogen peroxide production.
Table 1. Typical COFs as electrocatalysts for electrocatalytic hydrogen peroxide production.
ElectrocatalystTypeElectrolytenH2O2 Selectivity (%)FE (%)E0/V (vs. RHE)E1/2/V (vs. RHE)Jlim (mA cm−2)Reference
PYTA-TPEDH-COFMetal-free0.1 M KOH2.28–2.3682–85.8~800.69~0.602.14[70]
TPETA-TPEDH-COFMetal-free0.1 M KOH2.40–2.5075.2–79.8N/A0.69~0.601.9[70]
NQ-COFMetal-freepH 3.1 (acidic)N/A61–69N/AN/AN/AN/A[92]
TP-TD-COFMetal-free0.1 M KOH2.2481.9–86.2N/A0.760.62N/A[61]
Py-TD-COFMetal-free0.1 M KOH2.2–2.580–92N/A0.8340.6982.898[73]
Py-TD-COF-NHMetal-free0.1 M KOH2.8–3.050–61N/A0.8290.6932.891[73]
Br-COFMetal-free0.1 M KOH2.26–2.2985.4–85.580.60.70.612.34[93]
DFTAPB-TFTA-COFMetal-free0.1 M NaOH2.196.2571.10.698~0.601.7[16]
BUCT-COF-7/CNTMetal-free0.1 M KOH2.4183.4~800.82~0.71N/A[95]
TAE-COFMetal-free0.1 M KOHN/A98.273.0N/AN/AN/A[61]
cCTN:Cl−Metal-free0.1 M KOH2.285.3N/A0.75~0.60N/A[102]
TP-TTA-COFMetal-free0.1 M KOH2.58–2.6866.0–70.9N/A0.622~0.571.32[99]
COF-366Metal-free0.1 M KOH2.47864~0.60~0.51N/A[98]
MgP-DHTA-COFMetalated0.1 M KOH2.11–2.159690.60.680.62[101]
PtCl-COFMetalated0.1 M KOH2.26–2.3781.6–87.2N/A0.675~0.581.83[99]
CoPc-S-COFMetalated0.1 M KOH2.0–2.2~94~950.81~0.72N/A[100]
Py-Bpy-COF-ZnMetalated0.1 M KOH2.0699.1N/A~0.75~0.65N/A[96]
Ca-COF-318Metalated0.1 M KOH2.194–95910.750.612.8[97]
COF-366-CoMetalated0.1 M KOH2.29184~0.67~0.58N/A[98]
“N/A”: not available.
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Zheng, Y.; Zhao, Y.; Luo, W.; Zhang, Y.; Wang, Y.; Wu, Y. Rational Design Strategies for Covalent Organic Frameworks Toward Efficient Electrocatalytic Hydrogen Peroxide Production. Catalysts 2025, 15, 500. https://doi.org/10.3390/catal15050500

AMA Style

Zheng Y, Zhao Y, Luo W, Zhang Y, Wang Y, Wu Y. Rational Design Strategies for Covalent Organic Frameworks Toward Efficient Electrocatalytic Hydrogen Peroxide Production. Catalysts. 2025; 15(5):500. https://doi.org/10.3390/catal15050500

Chicago/Turabian Style

Zheng, Yingjie, Yi Zhao, Wen Luo, Yifan Zhang, Yong Wang, and Yang Wu. 2025. "Rational Design Strategies for Covalent Organic Frameworks Toward Efficient Electrocatalytic Hydrogen Peroxide Production" Catalysts 15, no. 5: 500. https://doi.org/10.3390/catal15050500

APA Style

Zheng, Y., Zhao, Y., Luo, W., Zhang, Y., Wang, Y., & Wu, Y. (2025). Rational Design Strategies for Covalent Organic Frameworks Toward Efficient Electrocatalytic Hydrogen Peroxide Production. Catalysts, 15(5), 500. https://doi.org/10.3390/catal15050500

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