MOF-on-MOF-derived CuO@In2O3 s-scheme heterojunction with core–shell structure for efficient photocatalytic CO2 reduction

Herein, a MOF-on-MOF-derived In2O3 nanosheets encapsulating CuO ortho-octahedral core–shell structure CuO@In2O3 S-Scheme heterojunction composite was designed and prepared by a new strategy of interfacial engineering integrating optical and catalytic activity centers, which endowed with the catalyst's dual properties of both highly efficient light absorption and charge separation. The In2O3 shell wraps around the CuO core in a tight coaxial contact, allowing them have the largest contact surface thus effectively promoting the transport of electrons and holes separated at the interface. More importantly, CuO@In2O3 formed a binuclear center could enhance the CO2 adsorption to facilitate the subsequent catalytic reaction and promote the charge transfer through Cu-O-In bonds. The successful construction of S-scheme heterojunction not only promotes the spatial separation of electron-hole pairs, but also maintains the strongest redox potentials of CuO and In2O3 at the conduction and valence band positions. Notably, the intermediates in the CO2 photoreduction process were probed by in situ infrared spectroscopy and a possible photocatalytic mechanism was hypothesized. Under visible light irradiation, the CuO@In2O3 rates of photocatalytic reduction of CO2 to produce CH4 and CO were 190.32 μmol g−1h−1 and 500.46 μmol g−1h−1, which are 2.1, 10.3 times and 2.4, 7.9 times higher than pristine CuO and In2O3, respectively. This work provides a feasible strategy for the design and synthesis of binuclear-centered photocatalysts with interfacial engineered modulation and application to the photocatalytic reduction of CO2.