ZIF-derived frame-in-cage hybrids of ZnSe–CdSe embedded within a N-doped carbon matrix for efficient photothermal conversion of CO2 into fuel

Abstract

Solar photocatalytic CO₂ reduction into valuable fuels shows great potential in solving the environmental and energy crises but remains a challenging goal. Herein, we present a strategy for the synthesis of frame-in-cage dodecahedral hybrids (ZnSe–CdSe@NC FC) composed of ZnSe–CdSe heterojunctions embedded within a nitrogen-doped carbon matrix through the simultaneous selenization and decomposition of a Zn-zeolitic imidazolate framework (ZIF-8) and the subsequent cation-exchange reaction with the assistance of ascorbic acid. The frame-in-cage microstructure of the dodecahedral particles can be obtained at a relatively low ramping rate (2 °C min⁻¹). The conversion from ZnSe@NC FC to ZnSe–CdSe@NC FC and CdSe@NC FC can be realized by extending the cation-exchange reaction time with the assistance of ascorbic acid. In the ZnSe–CdSe@NC FC catalyst, the ZnSe–CdSe heterojunction and the unique frame-in-cage structure could provide effective mass/charge transfer, abundant active sites, and enhanced incident light utilization. Meanwhile, the high light-to-heat conversion ability of nitrogen-doped carbon realizes a photothermal synergistic effect throughout the photocatalytic process. These advantages make the ZnSe–CdSe@NC FC with optimized composition exhibit superior activity and high stability in photo-thermocatalytic CO₂ reduction with a higher CO generation rate of 31.62 μmol h⁻¹ g⁻¹, which is much higher than that under single photocatalysis and thermocatalysis conditions. This work provides a promising strategy to design desired catalysts for photo-thermocatalytic CO₂ reduction.