The oxygen evolution reaction (OER) is a critical electrochemical reaction in water splitting and rechargeable metal–air batteries. It plays a pivotal role in achieving high-efficiency clean-energy production and energy storage in these devices. Transition metal-based bimetallic MOFs (TMB MOFs) with two different metal ions possess specific synergistic effects, which could exhibit OER performance and stability superior to those of the corresponding monometallic MOFs for water oxidation. Benefiting from the diversity of chemical composition and structural type, TMB MOFs can also serve as precursors and templates to obtain alloy-particle-decorated carbon materials with high surface area, or metal compounds such as bimetallic sulfides, phosphides, and hydroxides with atomic-level mixing of heterometallic elements. These materials with high-density active sites exhibit much improved catalytic activity in the water oxidation reaction. This article aims to review the recent progress with TMB MOFs and their derivatives in relation to applications as electrocatalysts in OER, including analysis of the mechanism of the OER process with the assistance of DFT calculations and in situ or operando techniques.

Novel polyaniline–graphitic carbon nitride (PANI–g-C₃N₄) composite photocatalysts with different PANI:g-C₃N₄ ratios were synthesized by “in situ” deposition oxidative polymerization of aniline monomer in the presence of g-C₃N₄ powder cooled in an ice bath. The resulting PANI–g-C₃N₄ composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The photoelectrochemical measurements were performed using several on–off cycles of visible light irradiation. The photocatalytic activities of the novel photocatalysts were evaluated using methylene blue as a target pollutant. The PANI–g-C₃N₄ composites exhibit obviously enhanced photocatalytic performance under visible light irradiation, which is much higher than that of TiO₂ (P25). The synergistic effect between PANI and g-C₃N₄ is found to lead to an improved photo-generated carrier separation. A possible photocatalytic mechanism of PANI on the enhancement of visible light performance is proposed to guide further improvement of their photocatalytic activity.

Photocatalytic conversion of CO₂ to methane faces challenges due to the stability of CO₂, unpredictable intermediates, and complex electron transfer steps. Herein, a spatial In₂S₃/In₂O₃ heterojunction with abundant S vacancies (ISIO(V_S)) is obtained through facile Polyvinylpyrrolidone (PVP) treatment to reach a methane yield of 16.52 µmol·g⁻¹·h⁻¹ with a selectivity of 95.93%, which is the highest among reported In₂S₃ and In₂O₃ based catalysts. The work function (W_f), differential charge density, and Kelvin Probe Force Microscopy (KPFM) results confirm that S vacancies strengthen the built‐in electric field (BEF) of In₂S₃/In₂O₃ (ISIO) heterojunctions, improving carrier separation. Density functional theory (DFT) calculations reveal that S vacancies induce electron redistribution, facilitating adsorption and activation of CO₂ and *CO intermediate, thus promoting hydrogenation to yield *CHO. The reaction pathway of photocatalytic CO₂ reduction is revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and Gibbs free energy (ΔG). The S vacancies modify electronic orbitals and the highest occupied molecular orbital (HOMO) of In atom, resulting in a stronger interaction between the catalyst and *CHO, which reduces ΔG_*CHO and regulates the selectivity of CH₄. This study paves a new avenue for the design of photocatalysts with highly selective reduction of CO₂ to CH₄ through defect engineering.

A novel and facile synthetic route toward Ag@AgCl nanoframe photocatalysts is developed. The AgCl nanoframes were initially prepared via a site-selected growth process. After light irradiation, the Ag@AgCl composite nanoframes with uniform distribution of Ag nanoparticles on the surface were successfully synthesized. The physical and photophysical properties of the Ag@AgCl composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) and photoluminescence spectroscopy (PL). The Ag@AgCl nanoframes showed superior photocatalytic activity and photo-generated charge carrier separation efficiency under visible light irradiation, when compared with pure AgCl and Ag@AgCl cubic structures. Furthermore, the Ag@AgCl nanoframes can maintain photocatalytic activity after 5 cycles. A possible mechanism for Ag@AgCl nanoframe structures is proposed. The enhanced photocatalytic activity of Ag@AgCl nanoframe structures can be attributed to the surface plasmon resonance (SPR) effect from Ag and the hybrid effect from AgCl.