Metal-organic frameworks with dinuclear metal centers for synergistically boosting CO2 photoreduction

Abstract

Dinuclear metal synergistic catalysis (DMSC) has been proved powerful in boosting CO₂ reduction, while this has not been achieved in heterogeneous catalysts with long-range order structures. In this study, we, by introduction of metal catalytic centers into an indium-based metal-organic framework (MOF), obtained a series of isostructural In-MOFs, including three MOFs with mononuclear metal catalytic center (M-In), three MOFs with dinuclear homometallic catalytic centers (MM-In), and three MOFs with dinuclear heterometallic catalytic centers (MM′-In, M/M′ = Co(II), Ni(II), Zn(II)). It was found that all these MOFs can serve as catalysts for photochemical CO₂ reduction to CO. Compared with M-In, the catalytic activities of MM-In were obviously enhanced, and that of MM′-In was further significantly enhanced. For example, the CO yield of CoZn-In reaches a record value of 12,700 µmol g⁻¹ h⁻¹, which is 4.0, 8.1, 9.4, and 18.6-fold higher than that of CoCo-In, ZnZn-In, Co-In, andZn-In, respectively. Similarly, the catalytic activities of CoNi-In and NiZn-In also show different fold increase than those of corresponding dinuclear homometallic and mononuclear metallic MOFs. The results of control experiments and theoretical calculation reveal that the higher catalytic activities of MM-In over M-In can be ascribed to the DMSC effect, and the higher catalytic activity of MM′-In over MM-In can be ascribed to the strengthened DMSC effect. The work reveals the relationship between DMSC effect and bimetal centers in CO₂ reduction, which provides new insights into the DMSC and paves a new way to design highly active catalysts for photochemical CO₂ reduction.