Boosting Photocatalytic CO₂ Cycloaddition with Epoxide over Facet-Dependent Cu₂O@Cu₃(HHTP)₂ Heterojunctions

The design of organic–inorganic heterojunctions can facilitate the separation of photoinduced charge carriers by modulating the electronic structure at the surface and interface states, showing promising applications in the field of photocatalytic CO2 cycloaddition. However, the details of the surface/interface effects between these two components are still poorly understood. Herein, Cu2O@Cu3(HHTP)2 (HHTP = 2, 3, 6, 7, 10, 11-hexahydroxytriphenylene) heterojunctions were synthesized, where Cu2O nanoparticles (NPs) featuring distinct crystal facets were utilized as substrates for the in situ growth of the copper-based metal–organic framework (Cu3(HHTP)2). Among them, t-Cu2O@Cu3(HHTP)2, centered on t-Cu2O with {111} and {100} facets, exhibits superior performance toward photocatalytic CO2 cycloaddition to chlorinated propylene carbonate, with a conversion efficiency of 372 mmol g–1 h–1 under light. Notably, single-particle spectroscopy reveals a more efficient photogenerated carrier transfer between t-Cu2O and Cu3(HHTP)2. The results confirm that crystalline facet dependence is a key factor in semiconductor photocatalysis and an important strategy for optimizing the reactivity of photocatalysts, which provides a way to improve the photocatalytic CO2 cycloaddition performance by modulating the interfacial states of organic–inorganic heterojunction structures.