Aug 2026· ACS Applied Energy Materials· 0 citations· 41 references
Abstract
Covalent organic frameworks (COFs) have attracted considerable attention as promising photocatalysts for hydrogen peroxide (H2O2) production. To further improve their catalytic performance, a quaternary ammonium functionality was introduced into the bipyridine units of the COF via a post-synthetic modification strategy. Under identical irradiation conditions, the cationized Pry-COF-QA achieved a H2O2 production rate of 7.31 mmol·h–1·g–1, which is markedly higher than that of the non-protonated Pry-COF (5.50 mmol·h–1·g–1). To gain mechanistic insight into the enhanced activity, density functional theory (DFT) calculations were performed. The results indicate that the incorporation of the quaternary ammonium group fundamentally reconfigures the photophysical behavior. In addition to inducing a red shift in the absorption spectrum by narrowing the HOMO–LUMO energy gap, it more importantly converts the excitation character from a localized excitation (LE) state, which is unfavorable for charge separation, to an intramolecular charge transfer (ICT) state with well-separated spatial distribution. This efficient ICT pathway effectively suppresses electron–hole recombination, thereby significantly prolonging the lifetime of photogenerated charge carriers and ultimately facilitating efficient photocatalytic H2O2 production, while also providing a valuable guideline for the rational design of COF-based systems toward efficient photocatalytic H2O2 generation.
Photocatalytic CO2 reduction offers a compelling strategy for carbon neutrality, yet its efficiency is critically limited by both inefficient charge utilization and insufficient active-site modulation. In this study, a methyl-functionalized trinuclear copper building unit was introduced to successfully construct Me2-Cu3-PY-COF, while the unmodified Cu3-PY-COF was prepared as the control sample. The introduction of methyl groups enhances electron density, narrows the band gap, and promotes charge separation and transfer, thereby improving photocatalytic CO2 reduction performance. As a result, Me2-Cu3-PY-COF exhibited a CH4 production rate of 135.15 µmol·g-1·h-1 with a selectivity of 91.6%, which was higher than that of the control sample (86.09 µmol·g-1·h-1, 81.9%). Mechanistic studies reveal that CO2 is converted to CH4 via a stepwise hydrogenation pathway, with Cu3 clusters serving as the active sites undergoing partial reduction from Cu2+ to Cu+, while imine sites facilitate CO2 adsorption. Density functional theory (DFT) calculations demonstrate that methyl-induced electronic modulation improves CO2 and intermediate adsorption, which in turn promotes multi-electron reduction. This work promotes the research on the application of trinuclear copper cluster-based metal-covalent organic frameworks as photocatalysts.
Photocatalytic hydrogen peroxide (H2O2) generation via sunlight-driven water and oxygen reduction reactions presents a sustainable alternative to the energy-intensive anthraquinone process. Although metal-organic frameworks (MOFs) offer tunable platforms for photocatalysis, the influence of metal-ligand microenvironment modulation within isostructural systems remains largely unexplored. In this work, we report two chemically robust conjugated 3D MOFs, Mn-Tp and Fe-Tp, synthesized via a scalable, solvent-free mechanochemical route and their exploration as photocatalysts. Despite sharing identical topologies and morphologies, Mn-Tp exhibits markedly superior photocatalytic performance, achieving a remarkable H2O2 yield of 10,487 µmol g-1 h-1, an apparent quantum yield of 9.94% at 467 nm, and a solar-to-chemical conversion efficiency of 0.45%. Mechanistic investigations, supported by theoretical calculations, reveal that subtle differences in the metal-node microenvironment modulate the electronic structure, promote dual-channel H2O2 generation via oxygen reduction and water oxidation, and suppress decomposition pathways. This study highlights the crucial role of local redox tuning in enhancing photocatalytic functionality, providing a strategic blueprint for designing next-generation MOF-based catalysts for the sustainable production of oxidants.
K. C. Ranjeesh, Avanti Chakraborty, Pilar Pena Sánchez et al.· Angewandte Chemie· 0 citations
Solar-driven photocatalytic synthesis of hydrogen peroxide (H2O2) offers a sustainable alternative to the energy-intensive anthraquinone process. Donor-acceptor (D-A) covalent organic frameworks (COFs) are highly promising photocatalysts for this transformation; however, the precise correlation between electronic conjugation, D-A pairing, and catalytic efficiency remains poorly understood. Here, we systematically investigate the threshold of conjugation enhancement on photocatalytic H2O2 production by designing D-A COFs with varying degrees of π-conjugation. Using benzotrithiophene (BTT) as the electron donor, we integrated acceptor units featuring alkyne and extended-ring motifs (yielding TATAB-BTT and TATAP-BTT). We reveal a distinct structure-activity relationship: moderate conjugation (TATAB-BTT) optimizes energy-level matching and maximizes charge separation, achieving an outstanding H2O2 production rate of 1610.8 µmol g-1 h-1, outperforming the less-conjugated literature example, TAPB-BTT (557.0 µmol g-1 h-1). Conversely, excessive conjugation (TATAP-BTT) induces a structural mismatch that shifts the electronic configuration from D-A to D-D, severely trapping excitons and diminishing performance (780.0 µmol g-1 h-1. These findings demonstrate that an optimal conjugation threshold is critical for sustaining D-A charge-transfer dynamics, providing a fundamental molecular design principle for next-generation polymeric photocatalysts.
Mengying Fu, Zhiqing Lin, Song-Yuan Dai et al.· Small· 0 citations
Covalent organic frameworks (COFs) exhibit considerable potential as photocatalysts for H2O2 production through the oxygen reduction reaction (ORR) in water. However, their catalytic efficiency is often hindered by sluggish charge separation and a scarcity of sites for O2 activation. Here, a heterojunction of Ho-loaded ZIF-L/triazine-based COF (Ho-ZIF-L/TTA-COF) is designed and synthesized through the electrostatically induced π-π assembly for efficient photocatalytic H2O2 production. The optimized Ho-ZIF-L/TTA-COF heterojunction achieves an impressive H2O2 production rate of 7.19 mmol g-1 h-1 without any sacrificial agents under visible-light irradiation, representing a 7.6-fold enhancement compared to individual TTA-COF. Based on the results of in situ X-ray photoelectron spectroscopy and Kelvin probe force microscopy, the enhanced performance is mainly ascribed to the favorable electrons transfer from TTA-COF to ZIF-L then to the loaded Ho species for greatly enhancing charge separation. Noteworthily, Ho-ZIF-L possesses fully exposed Ho active sites and a large specific surface area, accounting for the efficient 2e- ORR dominated by the produced •O2 - radicals for H2O2 formation.
Xinyue Wei, Shuai Xu, Suinan Wang et al.· ChemSusChem· 1 citation
Metal-organic frameworks (MOFs) have attracted tremendous interest in the photocatalytic hydrogen evolution reaction (HER). Nevertheless, their practical catalytic performance is limited by the rapid recombination of photogenerated charge carriers and sluggish interfacial reaction kinetics. Herein, a hierarchically structured UiO-66-NH2(Hf) / ZnIn2S4 (denoted UN-66/ZIS) heterostructure was rationally fabricated via a solvothermal strategy to simultaneously regulate charge separation efficiency and optimize interfacial catalytic kinetics. Benefiting from the intimate heterointerface and built-in electric field, the optimized UN-66/ZIS sample exhibits remarkably improved visible-light absorption capability and charge transport efficiency, achieving a photocatalytic hydrogen production of 6052 ± 206 μmol·g-1, which greatly outperforms pristine UN-66 and ZIS. More importantly, in-situ X-ray photoelectron spectroscopy combined with density functional theory calculations directly unveils the mechanism of interfacial charge redistribution and directional electron transfer responsible for the enhanced carrier separation efficiency, offering mechanistic insights into the improved catalytic activity. Furthermore, loading of Pt cocatalyst effectively accelerates the surface hydrogen evolution kinetics. The corresponding hydrogen evolution rate increases to 14,403 ± 287 μmol·g-1·h-1, approximately seven times that of the Pt-free heterostructure. This work proposes a synergistic strategy integrating heterojunction engineering and cocatalyst modulation to simultaneously optimize light harvesting, charge separation and surface reaction kinetics, which provides new guidelines for the rational design of high-performance MOF/sulfide photocatalysts toward solar hydrogen production.
Tingting Yu, Yi-Qing Ran, Picheng Gong et al.· Journal of Colloid and Inter...· 0 citations
To address common challenges in photocatalytic water splitting for hydrogen (H2) production, such as slow hole consumption kinetics and uncontrolled oxidative side reactions, we have designed an innovative Zn0.5Cd0.5S/bimetallic cobalt/nickel polyphthalocyanine (denoted as ZCS/CoNiPPc) photocatalyst that forms a Schottky heterojunction. Notably, the ZCS/CoNiPPc-2 composite achieves highly efficient photocatalytic H2 evolution coupled with selective oxidation of benzyl alcohol to benzaldehyde (BAD), delivering high production rates of 40.3 mmol g-1 h-1 for H2 and 56.1 mmol g-1 h-1 for BAD, which are 3.7 and 1.6 times greater than that of pristine ZCS, respectively. Furthermore, experimental and density functional theory results confirm that the synergistic combination of the bimetallic polyphthalocyanine and the Schottky heterostructure enables directional spatial separation and rapid transport of photogenerated charge carriers while preserving the innate reduction capability of CoNiPPc and the oxidation selectivity of ZCS. This work offers a new route toward integrated photocatalytic systems capable of simultaneous hydrogen fuel generation and high-value-added organic synthesis.
