Hydrophobic Interface Engineering Enables Solar‐Driven CO Hydrogenation to Long‐Chain Hydrocarbons Under Ambient Pressure

ABSTRACT Water formed during solar‐driven CO hydrogenation induces surface hydroxylation and oxidation of active sites, leading to catalyst deactivation and altered product selectivity. Here, we report a hydrophobic C‐Fe 2 O 3 /Cu catalyst constructed by carbon doping, which tailors the surface chemistry to construct a water‐repellent interface, thereby suppressing H 2 O adsorption and preventing Cu deactivation. Under light irradiation and ambient pressure (0.1 MPa), the optimized 550C‐Fe 2 O 3 /Cu delivers 30.1% CO conversion with 86.0% C 2+ and 50.3% C 5+ hydrocarbon selectivity, while CH 4 is suppressed to below 9%, and stable operation is sustained for 70 h. Operando and ex situ characterizations indicate that the optimized hydrophobic catalyst (water contact angle 115.9°) regulates the local water microenvironment, thereby suppressing CO 2 formation and maintaining a CO 2 selectivity below 4.0%. Concomitantly, CO‐ and H 2 ‐ programmed temperature desorption/reduction reveal enhanced CO uptake and a favorable surface adsorption balance for C─C coupling. In situ optical spectroscopy and density functional theory suggest that the hydrophobic interface strengthens CO adsorption and thermodynamically favors key C─C coupling steps, including *CHO formation and *CH 2 CH 2 evolution. This hydrophobic‐surface strategy enables efficient and durable solar‐driven photothermal CO hydrogenation to long‐chain hydrocarbons under ambient pressure, providing a practical route toward sustainable liquid fuel synthesis.