Highly selective photocatalytic CO₂ reduction into C₂H₄ enabled by metal-organic framework-derived catalysts with...

The highly selective conversion of CO₂ into valuable C₂H₄ 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 NaBH₄ to obtain Cu⁰/Cu^δ+-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 C₂H₄ with a yield rate of 6.5 μmol g^-1 within 5 h due to its high Cu⁺ content. To the best of our knowledge, this C₂H₄ product selectivity is a record high among all the photocatalysts reported so far for photocatalytic CO₂ reduction. In contrast, R-Cu-BTC only forms CO as a product with a cumulative yield of 0.7 μmol g^-1 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 CO₂ activation and water oxidation performance. In addition, in situ Fourier transform infrared spectroscopy is used to determine the possible reaction pathway from CO₂ to C₂H₄ over R-MOF-74(Cu). This work demonstrates the great potential of MOF-derived photocatalysts for the conversion of CO₂ into C₂H₄ and provides guidance for future photocatalyst development.