Bifunctional Au@UiO-67-bpy-Cu Plasmonic Nanostructures for the Solar-Driven CO2 Reduction to Methanol

Abstract

Photocatalytic CO₂ reduction is gaining more interest as a sustainable route to produce methanol, a key starting material in the synthesis of many chemicals and a potential energy carrier. Here, metal-organic frameworks (MOFs) are used as platforms to integrate plasmonic Au nanospheres and Cu active centers in joint bifunctional hybrid photocatalysts. The methodology followed in obtaining stable Au@UiO-67-bpy-Cu MOFs is based on synthesizing Au@UiO-67-bypiridine (bpy) MOFs through a core-shell procedure, and then modifying them with Cu ions after their coordination with the bpy ligands. This gains the final structure regular coverage of active metal centers that can be excited by the interaction with the plasmonic nanospheres. In the absence of Au, the system demonstrates selectivity toward the formation of methanol under hole scavenger-free conditions owing to the excitation of the bpy-Cu complex with visible light. The obtained yield duplicates upon Au nanospheres incorporation as a result of the injection of hot electrons, excited by surface-mediated intraband processes, to the bpy-Cu states, thus increasing their CO₂ reduction efficiency. Additionally, the catalytic activity remains stable during four consecutive cycles.