Lactic acid photosynthesis via C-C cross-coupling over atomically dispersed Ba

Photocatalytic carbon-carbon coupling offers a route for converting plastic-derived chemicals into valuable multi-carbon products, yet uncontrolled coupling of intermediate limits efficiency and selectivity. Here, we report atomically dispersed barium species on titanium dioxide that act as frustrated Lewis pairs, enabling efficient and selective generation intermediates during the co-oxidation of ethylene glycol and methanol toward lactic acid. The barium species create interstitial states near the Fermi level, enhancing charge separation and surface redox activity. Meanwhile, barium sites promote the formation of transient •CHOHCH₂OH radicals from ethylene glycol, while lattice O generates stable *CH₃ intermediates from methanol. Their directed cross-coupling yields lactic acid at rate of 2.04 ± 0.08 mmol g^-1 h^-1 with 81.8 ± 2.4 % carbon selectivity, alongside H₂ evolution at 5.85 ± 0.23 mmol g^-1 h^-1. In this work, we show an alkaline-earth frustrated Lewis pairs for selective solar-driven cross-coupling reaction.