Photocatalytic CO2 conversion has been paid great attention in an effort to produce renewable hydrocarbon fuels in a sustainable manner using solar energy. However, new catalytic materials still need to be developed to improve the conversion efficiency, selectivity, and stability for practical applications. Here we report a ruthenium-based asymmetric catalyst immobilized onto a plasmonic Au/TiO2 heterostructure to efficiently and selectively convert CO2 into formic acid in an aqueous solution. The plasmonic heterostructure promotes multi-electron transfer towards the catalyst through efficient charge separation at a Schottky junction. The ruthenium complex is stably immobilized onto the heterostructure by two phosphonate groups, and the catalytic centre is stabilized by bidentate pi-backbonding. The photocatalytic structure exhibits a high turnover frequency of 1200 h(-1) at 360 mW cm(-2), a superior selectivity towards formic acid (similar to 95%) even at a low pH (similar to pH 3), and a remarkable reusability over 50 hours without loss of the catalytic activity.