MOF-based ternary nanocomposites for better CO2 photoreduction: roles of heterojunctions and coordinatively unsaturated metal sites

Abstract

Semiconductors are the most widely used catalysts for CO₂ photoreduction. However, their efficiencies are limited by low charge carrier density and poor CO₂ activation. Towards solving these issues, a metal–organic framework (MOF)-based ternary nanocomposite was synthesized through self-assembly of TiO₂/Cu₂O heterojunctions via a microdroplet-based approach followed by in situ growth of Cu₃(BTC)₂ (BTC = 1,3,5-benzenetricarboxylate). With increased charge carrier density and efficient CO₂ activation, the hybrid ternary nanocomposite exhibits a high CO₂ conversion efficiency and preferential formation of CH₄. Systematic measurements by using gas chromatography, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, and time-resolved in situ diffuse reflectance infrared Fourier transform spectroscopy reveal that the semiconductor heterojunction and the coordinatively unsaturated copper sites within the hybrid nanostructure are attributable to the performance enhancements.