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.