Construction of Cu metal-organic frameworks with mixed valence sites for photoelectrocatalytic CO2 reduction

Transforming Cu 2 O into a semiconducting Cu(I)-BTC MOF integrated with rGO/TiO 2 created a photo-stable photocathode with improved carrier transport and visible-light response. The Cu(I)-BTC@rGO/TiO 2 system shows good CO selectivity and durability under illumination, offering a promising route to MOF-based PEC CO 2 RR. Cuprous oxide (Cu 2 O) is a promising photocathode material for photoelectrochemical CO 2 reduction (PEC CO 2 RR) owing to its narrow bandgap and intrinsic catalytic activity. However, its practical application is severely hindered by photocorrosion under illumination, which limits the photostability and performance. To address this, a novel strategy to replace Cu 2 O entirely with a semiconducting Cu-based metal-organic framework (MOF) was proposed. The low-coordinated Cu + centers, structural defects, anchoring on reduced graphene oxide (rGO), and TiO 2 endow the MOF with enhanced conductivity and visible-light response. The fabricated Cu(I)-Trimesic acid (BTC)@rGO/TiO 2 shows high CO Faradaic efficiency and much better photostability over 24 h compared with Cu 2 O. This work offers a new strategy to engineer stable, active MOF-based photocathodes for CO 2 conversion.