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

Abstract

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 (R_electron) 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.