Selective Reduction of Bimetallic Metal-Organic Frameworks to Construct Bifunctional Photothermal Catalysts

The reduction of bimetallic metal-organic frameworks (MOFs) can provide a potent strategy to adjust both metal valence states and porous structure, thereby engendering considerably enhanced functionality. Herein, a selective reduction strategy was applied to a bimetallic CoMg-MOF due to the distinct reduction potentials of Co and Mg, wherein Co(II) is partially reduced to Co(0), while Mg(II) remains intact within the same building units. The resulting material, R-CoMg, retains the original MOF-74 crystal structure and hexagonal prismatic morphology while featuring a hierarchical micromesoporous architecture arising from partial dissociation of Co-ligand bonds. Specifically, the synergistic interplay between the bimetallic active sites, complemented by the reduction-generated low-valence cobalt species, contributes to enhanced catalytic performance of R-CoMg. Meanwhile, its porosity facilitates efficient mass transfer and, by prolonging photon propagation paths and boosting light absorption, gives R-CoMg excellent photothermal conversion capability. Leveraging these structural attributes, R-CoMg, as a bifunctional photothermal catalyst, achieved a 90.7% yield in the CO2 cycloaddition reaction and delivered 97.1% degradation of Congo red within 25 min via peroxymonosulfate activation under simulated solar irradiation. This work establishes a novel and feasible approach to selective reduction for constructing high-performance MOF-based catalysts through precise valence-state and porosity engineering, offering new insights into the design of multifunctional materials for environmental applications.