CO Photoreduction by HO: Cooperative Catalysis of Palladium Species on Poly(triazine imide) Crystals.

Photocatalytic CO reduction coupled with HO oxidation has been pursued extensively, albeit facing challenges in efficiency and selectivity. Herein, we develop a Pd/PTI catalyst by co-anchoring atomic and nanoparticulate Pd species on poly(triazine imide) crystals, which exhibits high activity, selectivity, and stability for CO reduction to CO using HO as the reductant. Combined experimental and theoretical studies reveal that the dual Pd species synergistically enhance charge separation and transfer while promoting CO activation, CO desorption, and HO dissociation. Photo-stimulated electrons migrate to Pd nanoparticles to reduce CO, and holes oxidize Pd sites to Pd species that catalyze HO splitting to OH* and H*. The resulting H* spills onto adjacent Pd nanoparticles to support proton-coupled CO reduction, whereas OH* is oxidized by Pd to evolve O, regenerating Pd, and closing the catalysis cycle. Importantly, the photoinduced Pd sites dynamically modulate the local adsorption environment, weakening *CO binding on nearby Pd nanoparticles. This facilitates *CO desorption and hampers its hydrogenation to CH, enabling high CO selectivity. The optimal catalyst achieves a CO yield rate of 22.2 mmol g  h with 95.7% selectivity, stably operating over 30 h.