Self-assembly of a heterogeneous microreactor with carbon dots embedded in Ti-MOF derived ZnIn2S4/TiO2 microcapsules for efficient CO2 photoreduction

The assembly of the heterogeneous microreactor is a promising approach for CO2 photoreduction attributed to its abundant microchannel, intimate contact, high exposed surface area, and favorable heat-mass transfer. Herein, we developed a metal–organic framework (MOF) derived in situ transformation strategy to construct a carbon dot (CD)-decorated ZnIn2S4/TiO2 (CDs/ZIS/TiO2) microreactor. Taking advantages of this hierarchical structure, the CDs/ZnIn2S4/TiO2 microreactor exhibits significantly enhanced photocatalytic CO2 reduction activity with a CH4 yield of 14.9 μmol g−1 h−1 and CH4 selectivity of 75.6% in the absence of a sacrificial agent, where the electron consumption rate (Relectron) of 157.6 μmol g−1 h−1 is 1.9 and 18.3 times higher than those of ZIS(60)/TiO2 and bare ZnIn2S4, respectively. The combination of transient photo-induced voltage (TPV), in situ Fourier transform infrared and electron spin resonance (ESR) spectra illustrate the photocatalytic mechanism and the effect of CDs on the electron transfer behavior. This work emphasizes a facile technique for developing a CD-based microreactor to achieve high-efficiency photocatalytic CO2 reduction performance.