Built-In Electric Field Directs Electron Transport at Ultrathin Ni(OH)2/Metal–Organic Framework Interface for Efficient Photocatalytic CO2 Reduction

Rational design of heterojunctions as photocatalysts that can help alleviate the energy and environmental crisis relies on the efficient electron transfer to the catalytically active sites. In this work, a robust metal–organic framework (MOF)-based heterostructured catalyst for the CO2 reduction reaction (CRR) was reported, taking advantage of a synergy effect between ultrathin (1.5 nm thickness) Ni-rich Ni(OH)2 nanosheets (NSs) and the highly stable and conductive Fe-rich Prussian blue (PB). This Ni(OH)2/PB photocatalyst can attain an optimal CO evolution rate of 108.8 mmol h–1 g–1 and a high CO selectivity (88.2–95.0%) in the CRR. The stable PB helps atomically thin Ni(OH)2 NSs to be well-dispersed and exposed in the heterojunction. A built-in electric field found at the interface of the bulk-sized PB and the ultrathin Ni(OH)2 further directs the electron transfer. Intriguingly, the conductive PB can quickly capture the electrons from the Ru-based photosensitizer and then rapidly sends them to the CRR-active Ni(OH)2 in the Z-scheme Ni(OH)2/PB system, accounting for its high efficiency and high selectivity over CO2 reduction into CO. The findings underline the versatility and the mechanistic response of MOFs in constructing advanced catalysts.