Highly selective photocatalytic CO reduction into CH enabled by metal-organic framework-derived catalysts with high Cu content.

The highly selective conversion of CO into valuable CH is a highly important but particularly challenging reaction. Herein, the metal-organic frameworks MOF-74(Cu) with infinite Cu(II)-O chains and Cu-BTC (BTC=benzene-1,3,5-tricarboxylate) with paddle-wheel binuclear Cu(II) clusters are used as precursors. These MOFs are reduced by NaBH to obtain Cu/Cu-based photocatalysts denoted as R-MOF-74(Cu) and R-Cu-BTC, respectively. Significantly, R-MOF-74(Cu) achieves a high selectivity of 90.2 % for CH with a yield rate of 6.5 μmol g within 5 h due to its high Cu content. To the best of our knowledge, this CH product selectivity is a record high among all the photocatalysts reported so far for photocatalytic CO reduction. In contrast, R-Cu-BTC only forms CO as a product with a cumulative yield of 0.7 μmol g within 5 h. Photoelectrochemical characterization and electron paramagnetic resonance results show that R-MOF-74(Cu) has low interfacial transfer resistance, high photogenerated electron separation efficiency, and excellent CO activation and water oxidation performance. In addition, in situ Fourier transform infrared spectroscopy is used to determine the possible reaction pathway from CO to CH over R-MOF-74(Cu). This work demonstrates the great potential of MOF-derived photocatalysts for the conversion of CO into CH and provides guidance for future photocatalyst development.