Heterojunction T-ZIF-8/SnO₂ Composite Photocatalysts by Sol–gel Method for CO₂ Reduction

Artificial photocatalysis is widely used to capture CO₂ for conversion into a range of usable carbon-containing fuels. SnO₂ and T-ZIF-8 materials have attracted much attention due to their distinctive physicochemical properties. In this paper, addressing the low efficiency of SnO₂ and T-ZIF-8 in the photocatalytic reduction of CO₂, a novel heterojunction composite photocatalyst of SnO₂ and T-ZIF-8 was designed and synthesized using the sol–gel method. This approach combines the respective advantages of SnO₂ and T-ZIF-8 materials. The resulting composite material has good photoresponsivity in the range of 200 ~ 800 nm. The conversion of CO₂ to CO and CH₄ under visible light irradiation is improved in T-ZIF-8/SnO₂ composites compared to SnO₂ and T-ZIF-8. The CO production rate reaches up to 16.6 µmol·g⁻¹·h⁻¹, and the CH₄ production rate reaches up to 14.7 µmol·g⁻¹·h⁻¹, with a selectivity for CH₄ as high as 77%. Mechanistic analysis indicates that the T-ZIF-8/SnO₂ heterojunction significantly promotes the separation of photogenerated electron–hole pairs in the photocatalyst. This work presents an effective method for enhancing the catalytic activity of ZIF-based materials, opening up a new pathway for the environmentally friendly conversion of CO₂ into clean fuels.