Two-electron Oxygen Reduction Research Articles

Hydrogen Radical Enabling Industrial-Level Oxygen Electroreduction to Hydrogen Peroxide.

The electrochemical synthesis of hydrogen peroxide from oxygen and water, powered by renewable electricity, provides a highly attractive alternative to the energy-intensive autoxidation process presently used in industry, but much remains unknown about this two-electron oxygen reduction reaction (2e-ORR), especially the local proton effect. Here, we have investigated the function of hydrogen-associated intermediates in the 2e-ORR using a rationally designed cooperative electrode material with cobalt (II) clusters embedded onto the oxidized carbon nanotube composites (Co-OCNT). We found that the local proton availability can determine both the reaction kinetics and selectivity. A 2e-ORR process involving hydrogen radical transfer is confirmed. Specifically, the carbon sites from the OCNTs promote proton production, and the cobalt sites from the Co cluster facilitate ORR intermediate formation. The high local proton availability and the cooperative dual-active sites both contribute to the superior reaction kinetics and selectivity of the Co-OCNT, reaching an H2O2 production rate of ~40.6 mol gcat -1 h-1 and a faradaic efficiency of 90 % at a current density of 300 mA cm-2. Further cascading the 2e-ORR with the electro-Fenton process shows a high selectivity of oxalic acid up to 97 % for the valorization of ethylene glycol.

Room temperature oxygenated groups addition in carbon materials via ozone oxidation for boosting electrochemical H2O2 production

The crucial yet delicate 2e− oxygen reduction reaction (ORR) for producing the green chemical H2O2 relies on the uniform coordination environment of the active sites, such as oxygenated groups in metal-free carbon material catalysts. However, conventional harsh carbon material synthesis methods inevitably introduce structural defects and alter morphology, hindering the precise control of active site formation. Herein, we developed the ozone oxidation method under controlled reaction conditions to precisely modify carbon materials at room temperature. Through controlling the ozonation of reaction time, concentration, temperature, and relative humidity, we find the mild method allows us to precisely add active carboxyl group (–COOH) without forming structural defects. Electrochemical tests reveal that the optimal catalyst with the highest –COOH content exhibits the most outstanding mass activity of 164 A/g at 0.65 V and the highest H2O2 selectivity of 91 %. The density functional theory calculations demonstrate that the carbon sites directly connected to –COOH possess the optimized binding strength of *OOH intermediate to favor the two-electron oxygen reduction process. This work offers a novel approach to precisely and gently control carbon surface groups while preserving the structural morphology through ozone gas treatment, which can be readily applied to other material designs.

Hydrogen Peroxide Electrosynthesis via Selective Oxygen Reduction Reactions Through Interfacial Reaction Microenvironment Engineering.

The electrochemical two-electron oxygen reduction reaction (2e- ORR) offers a compelling alternative for decentralized and on-site H2O2 production compared to the conventional anthraquinone process. To advance this electrosynthesis system, there is growing interest in optimizing the interfacial reaction microenvironment to boost electrocatalytic performance. This review consolidates recent advancements in reaction microenvironment engineering for the selective electrocatalytic conversion of O2 to H2O2. Starting with fundamental insights into interfacial electrocatalytic mechanisms, an overview of various strategies for constructing the favorable local reaction environment, including adjusting electrode wettability, enhancing mesoscale mass transfer, elevating local pH, incorporating electrolyte additives, and employing pulsed electrocatalysis techniques is provided. Alongside these regulation strategies, the corresponding analyses and technical remarks are also presented. Finally, a summary and outlook on critical challenges, suggesting future research directions to inspire microenvironment engineering and accelerate the practical application of H2O2 electrosynthesis is delivered.

A Chlorine-Resistant Self-Doped Nanocarbon Catalyst for Boosting Hydrogen Peroxide Synthesis in Seawater.

Developing seawater-compatible hydrogen peroxide electroproduction technologies is crucial for advancing marine resource utilization in coastal regions. However, designing efficient and highly stable non-noble metal catalysts for two-electron oxygen reduction reaction in seawater environment remains a challenging task due to the corrosive and toxic nature of chloride ions (Cl-). Herein, we present, for the first time, a novel nitrogen and oxygen self-doped defect-rich nanocarbon (NO-DC700) catalyst, derived from silk fiber, which addresses these challenges with low toxicity, cost-effectiveness, and high adaptability. The obtained NO-DC700 catalyst demonstrates an impressive H2O2 production rate of up to 4997 mg L-1 h-1, a high Faradaic efficiency of 96.5%, and produces 4.3 wt.% H2O2 after 20 hours of stable operation, placing it among the highest-performing catalysts reported in neutral electrolytes. Theoretical calculations reveal that NO-DC700's superior 2e- ORR performance is due to the synergistic effect of graphitic nitrogen and C-OH, which inhibits Cl- adsorption and promotes *OOH adsorption. Additionally, integrating 2e- ORR with Fenton-like technology enables rapid degradation of organic pollutants and effective inactivation of seawater algae, offering significant potential for mitigating coastal eutrophication and red tide pollution. This work provides valuable insights into H2O2 electrosynthesis in seawater solution and promises advancements in ocean-energy applications.

Facet-dependent spatial separation of dual cocatalysts on MOF photocatalysts for H2O2 production coupling biomass oxidation with enhanced performance

Cooperative coupling of photocatalytic two-electron oxygen reduction reaction (2e-ORR) with oxidative organic synthesis holds great promise for sustainable production of valuable chemicals. To achieve high performance, the rational design of photocatalysts with effective electron-hole separation and redox capability is crucial. Herein, a MOF-based photocatalyst with crystal facet-dependent spatial separation of dual cocatalysts is constructed for photocatalytic 2e-ORR coupled with vanillyl alcohol oxidation reaction (VAOR). The facet-dependent growth of reductive Pd and oxidative CoOx cocatalysts respectively on the {100} and {001} facets of MIL-125-NH2 enables the directional migration of photogenerated carries, facilitating the charge separation for redox reactions. Additionally, the interaction between Pd and MIL-125-NH2 modulates the Pd sites into electron-sufficient state with upshifted d-band center, promoting the O2 activation and *OOH intermediate formation. The rationally designed composite photocatalyst delivers an excellent H2O2 yield of 74.8 mM g−1 h−1 and a high vanillic acid production rate of 80.9 mM h−1 g−1 with the conversion and selectivity of 96.8 % and 91.1 %, respectively.

Generative Pretrained Transformer for Heterogeneous Catalysts.

Discovery of novel and promising materials is a critical challenge in the field of chemistry and material science, traditionally approached through methodologies ranging from trial-and-error to machine-learning-driven inverse design. Recent studies suggest that transformer-based language models can be utilized as material generative models to expand the chemical space and explore materials with desired properties. In this work, we introduce the catalyst generative pretrained transformer (CatGPT), trained to generate string representations of inorganic catalyst structures from a vast chemical space. CatGPT not only demonstrates high performance in generating valid and accurate catalyst structures but also serves as a foundation model for generating the desired types of catalysts by text-conditioning and fine-tuning. As an example, we fine-tuned the pretrained CatGPT using a binary alloy catalyst data set designed for screening two-electron oxygen reduction reaction (2e-ORR) catalyst and generated catalyst structures specialized for 2e-ORR. Our work demonstrates the potential of generative language models as generative tools for catalyst discovery.

Ionic liquid modifying conductivity and hydrophobicity of B4C for enhanced electrosynthesis of H2O2

Electrosynthesis of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (2e− ORR) is an attractive energy-efficient and decentralized alternative to the conventional anthraquinone process. However, designing non-precious metal catalysts with high activity, selectivity and stability is a great challenge. Here, we report a facile and effective approach to improve the catalytic performance of commercial boron carbide (B4C) by loading ionic liquid (IL), which exploits the complementary properties of high electrical conductivity and hydrophobicity of IL. The B4C catalyst with optimal IL loading possesses the highest conductivity and O2 adsorption, exhibiting high H2O2 selectivity in both neutral (∼96 %) and alkaline (∼93 %) electrolyte, which are nearly ∼34 % and ∼19 % higher than pristine B4C, respectively. Moreover, its production rate is ∼1.5 times that of pristine B4C at 130 mA cm−2 current density, resulting in a high concentration of H2O2 (5.93 wt%) produced in flow-cell reactor. The long-term cycle test demonstrates the desirable stability of IL@B4C/GDE, which is attributed to the high hydrophobicity and tight bonding between IL@B4C and the substrate, giving a strong flood-proof capability at the three-phase interface and avoiding rapid flooding by the electrolyte. This work provides new insights into designing non-precious metal electrocatalysts for efficient electrosynthesis of H2O2, emphasizing the role of IL in interface engineering.

Membrane-free Electrolysis Production of Hydrogen Peroxide on Low-cost Metal-free Electrocatalysts for Dye Degradation.

The efficient production of hydrogen peroxide (H2O2) solution was achieved by combining cathodic two-electron oxygen reduction (2e- ORR) and anodic two-electron water oxidation (2e- WOR) in two half-reaction cells. h-BN loaded on carbon fibers (h-BN@C) is prepared and employed as an anode material to catalyze 2e- WOR, while sulfonated commercial BP-2000 carbons (BP-2000-SO3H) were prepared as the cathode materials for 2e- ORR. In a 2 M KHCO3 solution, an overall Faradaic efficiency of 97 % and a total H2O2 production rate of 1872 mmol g-1 h-1 over metal-free electrodes were accomplished in a membrane-free flow cell. The dilute H2O2 solution could be directly used to degrade cationic Rhodamine B or methyl blue and anionic methylene orange dyes in water. This work proved low-cost production of dilute H2O2 solution in simple membrane-free flow cells with single electrolyte and on-site utilization for efficient dye degradation.

Nature-Inspired N, O Co-Coordinated Manganese Single-Atom Catalyst for Efficient Hydrogen Peroxide Electrosynthesis.

The two-electron oxygen reduction reaction (2e- ORR) is a pivotal pathway for the distributed production of hydrogen peroxide (H2O2). In nature, enzymes containing manganese (Mn) centers can convert reactive oxygen species into H2O2. However, Mn-based heterogeneous catalysts for 2e- ORR are scarcely reported. Herein, we developed a nature-inspired single-atom electrocatalyst comprising N, O co-coordinated Mn sites, utilizing carbon dots as the modulation platform (Mn CD/C). As-synthesized Mn CD/C exhibited exceptional 2e- ORR activity with an onset potential of 0.786 V and a maximum H2O2 selectivity of 95.8 %. Impressively, Mn CD/C continuously produced 0.1 M H2O2 solution at 200 mA/cm2 for 50 h in the flow cell, with negligible loss in activity and H2O2 faradaic efficiency, demonstrating practical application potential. The enhanced activity was attributed to the incorporation of Mn atomic sites into the carbon dots. Theoretical calculations revealed that the N, O co-coordinated structure, combined with abundant oxygen-containing functional groups on the carbon dots, optimized the binding strength of intermediate *OOH at the Mn sites to the apex of the catalytic activity volcano. This work illustrates that carbon dots can serve as a versatile platform for modulating the microenvironment of single-atom catalysts and for the rational design of nature-inspired catalysts.

Defect engineering induced high metal loading Co-single-atom catalyst on carbon dots for efficient H2O2 electrosynthesis

Co-single atom catalysts (Co-SACs) exhibit high selectivity and efficiency for H2O2 electrosynthesis via the two-electron oxygen reduction reaction (2e−ORR), with the catalytic activity as significantly influenced by the loading content of Co atoms. However, the loading of Co atoms is typically confined to a low level (<1.0 wt%), which restricts their overall catalytic performance. Herein, we proposed a defect engineering strategy that utilized the carbon dots (CDs) as a platform to capture Co atoms, and constructed a series of Co-SACs with high Co atoms loading (with a maximum of 6.16 wt%), representing a substantial improvement compared to existing benchmarks in the literature. Experimental and characterization results revealed that the defect sites on CDs allowed adequate spacing between the Co atoms, effectively preventing their aggregation and promoting the generation of highly loaded metal atoms. It is worth noting that ECDs-CoSA demonstrated remarkable efficacy and catalytic activity with 93.70 % H2O2 selectivity and an impressive H2O2 yield of 9.71 mol L−1 h−1 gcat.−1 in neutral condition. This study presents an effective route for the controlled prepared of Co-SACs with high metal loading, aiming at sustainable and the efficient H2O2 electrosynthesis.

Electrocatalysts for the Formation of Hydrogen Peroxide by Oxygen Reduction Reaction.

Hydrogen peroxide (H2O2) is a widely used strong oxidant, and its traditional preparation methods, anthraquinone method, and direct synthesis method, have many drawbacks. The method of producing H2O2 by two-electron oxygen reduction reaction (2e- ORR) is considered an alternative strategy for the traditional anthraquinone method due to its high efficiency, energy saving, and environmental friendliness, but it remains a big challenge. In this review, we have described the mechanism of ORR and the principle of electrocatalytic performance testing, and have summarized the standard performance evaluation techniques for electrocatalysts to produce H2O2. Secondly, according to the theoretical calculation and experimental results, several kinds of efficient electrocatalysts are introduced. It is concluded that noble metal-based materials, carbon-based materials, non-noble metal composites, and single-atom catalysts are the preferred catalyst materials for the preparation of H2O2 by 2e- ORR. Finally, the advantages and novelty of 2e- ORR compared with traditional methods for H2O2 production, as well as the advantages and disadvantages of the above-mentioned high-efficiency catalysts, are summarized. The application prospect and development direction of high-efficiency catalysts for H2O2 production by 2e- ORR has been prospected, which is of great significance for promoting the electrochemical yield of H2O2 and developing green chemical production.

Rational design of an air-breathing gas-diffusion electrode with oxygen vacancy-rich ZnO for robust and durable H2O2 electrosynthesis

Developing cost-effective and durable cathodes with outstanding oxygen mass transport and selective two-electron oxygen reduction reaction (ORR) is crucial for large-scale H2O2 electrosynthesis. Herein, an oxygen vacancy-rich ZnO-modified air-breathing gas-diffusion electrode (ZnO-V/GDE) was fabricated, thus eliminating the cost of aeration while achieving remarkable O2 utilization efficiency and H2O2 selectivity. This novel cathode led to ultrahigh H2O2 yield of 1005.2 mg L−1 with selectivity of 74.6 %, outperforming both the raw and ZnO-modified air-breathing GDEs. Moreover, the practical applicability of ZnO-V/GDE was demonstrated by its high stability and effectiveness when treating micropollutants in wastewater by ZnO-V/GDE-based electro-Fenton process. Mechanistic insights unveiled the key roles of oxygen vacancies, which not only facilitate the O2 transport by creating a superhydrophobic interface and provide binding centers to O2, but also reduce the energy barrier of the rate-determining step (OOH*-to-H2O2), eventually enhancing the ORR performance.

Modulating Core Polarity in Metal-free Covalent Organic Frameworks for Selective Electrocatalytic Hydrogen Peroxide Production.

Tuning the charge density at the active site to balance the adsorption ability and reactivity of oxygen is extremely significant for driving a two-electron oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2O2). Herein, we have highlighted the influence of intermolecular polarity in covalent organic frameworks (COFs) on the efficiency and selectivity of electrochemical H2O2 production. Different C3 symmetric building blocks have been utilized to regulate the charge density at the active sites. The benzene-cored COF, which exhibits reduced polarity than the triazine-cored COF, displayed enhanced performance in H2O2 production, achieving 93.1% selectivity for H₂O₂ at 0.4 V with almost two-electron transfer and a faradaic efficiency of 90.5%. In-situ electrochemical Raman spectroscopy and scanning electrochemical microscopy (SECM) were employed to confirm H₂O₂ generation and analyze spatial reactivity patterns. These techniques provided detailed insights into localized catalytic behavior, emphasizing the influence of core polarity.

Isolated Ni Atoms for Enhanced Photocatalytic H2O2 Performance with 1.05% Solar-to-Chemical Conversion Efficiency in Pure Water.

Photocatalytic hydrogen peroxide (H2O2) production encounters a major impediment in its low solar-to-chemical conversion (SCC) efficiency due to undesired H2O2 product decomposition. Herein, an isolated nickel (Ni) atom modification strategy is developed to adjust the thermodynamic process of H2O2 production to address the challenge. Sacrificial experiments and in situ characterization reveal that H2O2 generation occurs via a highly selective indirect two-electron oxygen reduction reaction. The optimized photocatalyst exhibits a remarkable H2O2 production rate of 338.9 μmol gcat-1 h-1 in pure water, representing a 48-fold enhancement. Notably, it attains an impressive SCC efficiency of 1.05%, surpassing that of current state-of-the-art catalysts. Theoretical insights reveal the downshifted d-band center facilitates moderate O2 adsorption and barrier-free *OOH conversion, favoring H2O2 release and preventing *H2O2 decomposition. This work showcases efficient H2O2 photosynthesis via d-band manipulation, presenting a fresh perspective for advancing high-efficiency SCC systems.

Perfect Is Perfect: Nickel Prussian Blue Analogue as A High-Efficiency Electrocatalyst for Hydrogen Peroxide Production.

Prussian blue analogues (PBA) are a large family of functional materials with diverse applications such as in electrochemical fields. However, their use in the emerging two-electron oxygen reduction reaction for clean production of hydrogen peroxide (H2O2) is lagging. Herein, a general solvent exchange induced reconstruction strategy is demonstrated, through which an abnormal NiNi-PBA superstructure is synthesized as a high-performance electrocatalyst for H2O2 generation. The resultant NiNi-PBA superstructure has a stoichiometric composition with saturated lattice water, and a leaf-like morphology composed of interconnected small-size nanosheets with identical orientation and predominate {210} side surface exposure. Our studies show that the Ni-N centers on {210} facets are the active sites, and the saturated lattice H2O favors a six-coordinated environment that results in high selectivity. The "perfect" structure including stoichiometric composition and ideal facet exposure leads to a high selectivity of ~100 % and H2O2 yield of 5.7 mol g-1 h-1, superior to the reported MOF-based electrocatalysts and most other electrocatalysts.

Host-guest-induced electronic state triggers two-electron oxygen reduction electrocatalysis

Supramolecular polymers possess great potential in catalysis owing to their distinctive molecular recognition and dynamic crosslinking features. However, investigating supramolecular electrocatalysts with high efficiency in oxygen reduction reaction to hydrogen peroxide (ORHP) remains an unexplored frontier. Herein, we present organic polymers for ORHP by introducing cyclodextrin-containing noncovalent building blocks, affording these supramolecules with abundant dynamic bonds. The electronic states and reaction kinetics are further well-modulated via a host-guest strategy, resulting in appropriate regional electron binding force and controllable chemical activity. Notably, integrating supramolecular units into phenyl group-containing model covalent polymer achieves a production rate of 9.14 mol g−1cat h−1, with 98.01% Faraday efficiency, surpassing most reported metal-free electrocatalysts. Moreover, the dynamic bonds in supramolecular catalysts can effectively regulate the binding ability of oxygen intermediates, leading to high reactivity and selectivity for the 2e− pathway. Supported by theory calculation and in situ experiment, C atoms (site–1) adjacent to the –C = N (N) group are potential active sites. This work pioneers host-guest strategy and provides inspiring ideas for the ORHP process.

Boosting the O2-to-H2O2 Selectivity Using Sn-Doped Carbon Electrocatalysts: Towards Highly Efficient Cathodes for Actual Water Decontamination.

The high cost and often complex synthesis procedure of new highly selective electrocatalysts (particularly those based on noble metals) for H2O2 production are daunting obstacles to penetration of this technology into the wastewater treatment market. In this work, a simple direct thermal method has been employed to synthesize Sn-doped carbon electrocatalysts, which showed an electron transfer number of 2.04 and outstanding two-electron oxygen reduction reaction (ORR) selectivity of up to 98.0 %. Physicochemical characterization revealed that this material contains 1.53 % pyrrolic nitrogen, which is beneficial for the production of H2O2, and -C≡N functional group, which is advantageous for H+ transport. Moreover, the high volume ratio of mesopores to micropores is known to favor the quick escape of H2O2 from the electrode surface, thus minimizing its further oxidation. A purpose-made gas-diffusion electrode (GDE) was prepared, yielding 20.4 mM H2O2 under optimal electrolysis conditions. The drug diphenhydramine was selected for the first time as model organic pollutant to evaluate the performance of an electrochemical advanced oxidation process. In conventional electro-Fenton process (pH 3), complete degradation was achieved in only 15 min at 10 mA cm-2, whereas at natural pH 5.9 and 33.3 mA cm-2, almost overall drug removal was reached in 120 min.

Selective O2-to-H2O2 Electrosynthesis by a High-Performance, Single-Pass Electrofiltration System Using Ibuprofen-Laden CNT Membranes.

Producing H2O2 through a selective, two-electron (2e) oxygen reduction reaction (ORR) is challenging, especially when it serves as an advanced oxidation process (AOP) for cost-effective water decontamination. Herein, we attain a 2e-selectivity H2O2 production using a carbon nanotube electrified membrane with ibuprofen (IBU) molecules laden (IBU@CNT-EM) in an ultrafast, single-pass electrofiltration process. The IBU@CNT-EM can generate H2O2 at a rate of 25.62 mol gCNT-1 h-1 L-1 in the permeate with a residence time of 1.81 s. We demonstrated that an interwoven, hydrophilic-hydrophobic membrane nanostructure offers an excellent air-to-water transport platform for ORR acceleration. The electron transfer number of the ORR for IBU@CNT at neutral pH was confirmed as 2.71, elucidating a near-2e selectivity to H2O2. Density functional theory (DFT) studies validated an exceptional charge distribution of the IBU@CNT for the O2 adsorption. The adsorption energies of the O2 and *OOH intermediates are proportional to the H2O2 selectivity (64.39%), higher than that of the CNT (37.81%). With the simple and durable production of H2O2 by IBU@CNT-EM electrofiltration, the permeate can actuate Fenton oxidation to efficiently decompose emerging pollutants and inactivate bacteria. Our study introduces a new paradigm for developing high-performance H2O2-production membranes for water treatment by reusing environmental functional materials.

Advancing Microbial Electrochemical H2O2 Synthesis by Tailoring the Surface Chemistry of Stereolithography-Derived 3D Pyrolytic Carbon Electrodes.

Microbial electrosynthesis of H2O2 offers an economical and eco-friendly alternative to the costly and environmentally detrimental anthraquinone process. Three-dimensional (3D) electrodes fabricated through additive manufacturing demonstrate significant advantages over carbon electrodes with two-dimensional (2D) surfaces in microbial electrosynthesis of H2O2. Nevertheless, the presence of oxygen-containing free acidic groups on the prototype electrode surface imparts hydrophilic properties to the electrode, which affects the efficiency of the two-electron oxygen reduction reaction for H2O2 generation. In this study, we elucidated that the efficiency of microbial H2O2 synthesis is markedly enhanced by utilizing oxygen-free 3D electrodes produced via additive manufacturing techniques followed by surface modifications to eradicate oxygen-containing functional groups. These oxygen-free 3D electrodes exhibit superior hydrophobicity compared to traditional carbon electrodes with 2D surfaces and their 3D printed analogues. The oxygen-free 3D electrode is capable of generating up to 130.2 mg L-1 of H2O2 within a 6-h time frame, which is 2.4 to 13.6 times more effective than conventional electrodes (such as graphite plates) and pristine 3D printed electrodes. Additionally, the reusability of the oxygen-free 3D electrode underscores its practical viability for large-scale applications. Furthermore, this investigation explored the role of the oxygen-free 3D electrode in the bioelectro-Fenton process, affirming its efficacy as a tertiary treatment technology for the elimination of micropollutants. This dual functionality accentuates the versatility of the oxygen-free 3D electrode in facilitating both the synthesis of valuable chemicals and advancing environmental remediation. This research introduces an innovative electrode design that fosters efficient and sustainable H2O2 synthesis while concurrently enabling subsequent environmental restoration.

Designing 1-nm-Thick MOF Nanosheets with Donor-Acceptor Complexes for Photosynthesis of H2O2 Using Water and Dioxygen Only.

Artificial photosynthesis of hydrogen peroxide (H2O2) presents a promising environmentally friendly alternative to the industrial anthraquinone process. This work designed ultrathin metal-organic framework (MOF) nanosheets on which porphyrin ligand as an electron donor (D) and anthraquinone (AQ) as an electron acceptor (A) are integrated as the D-A complexes. The porphyrin component allows the MOF nanosheets to absorb full-spectrum solar light while the acceptor AQ motif promotes central aluminum ion coordination, hindering layer stacking to achieve a thickness of 1.0 nm. The ultrathin D-A design facilitates the separation of electrons from the MOF skeleton to the AQ motif, which induces the direct two-electron oxygen reduction reaction (ORR) mediated by the reversible redox couple of AQ-AQH2 and multielectron water oxidation reaction (WOR) driven by holes remaining on the porphyrin part. In O2-saturated water, the ultrathin MOF nanosheets outperformed the AQ-free bulk and multilayered counterparts by 2.9 and 2.6 times in H2O2 production, respectively, achieving the apparent quantum yield of 4.8% at 420 nm. It also surpasses other benchmark photocatalysts, including the typical MOF photocatalyst, MIL-125-NH2, and organic polymeric photocatalysts. The ultrathin D-A MOF photocatalyst generated H2O2 via both two-electron ORR as a major path and two-electron WOR as a minor path. This approach presents a promising strategy for the rational design of efficient nanostructured photocatalysts for solar fuels and chemicals.