Self-Supporting Triphase Photocatalytic CO2 Reduction to CH3OH on Controllable Core–Shell Structure with Tunable Interfacial Wettability

Enhancing the CO2 mass transfer and proton supply in the photocatalytic reduction of CO2 with H2O into CH3OH (PRC-M), while avoiding the hydrogen evolution reaction (HER), remains a challenge. Herein, we propose an approach to control the surface coverage of CO2 and H2O by modifying interfacial wettability, which is achieved by modulating the core-shell structure to expose either hydrophobic melamine-resorcinol-formaldehyde (MRF) or hydrophilic NiAl-layered double hydroxides (NAL). Characterizations reveal that an insufficient proton supply leads to the production of competing CO, while excessive coverage of H2O results in undesired HER. The NAL-MRF integrates hydrophobic and hydrophilic interfaces, contributing to the CO2 mass transfer and H2O adsorption, respectively. This combination forms a microreactor that facilitates the triphase photocatalysis of CO2, H2O, and catalyst, allowing for high local concentrations of both *CO and *H without competing binding sites. Importantly, the formation of covalent bonds and a Z-type heterojunction between hydrophilic NAL and hydrophobic MRF layers accelerates the charge separation. Furthermore, the density functional theory results indicate that the NAL linking promotes the continuous hydrogenation of *CO. As a result, an enhanced CH3OH yield of 31.41 μmol g-1 h-1, with selectivity of 93.62%, is achieved without hole scavengers or precious metals.