Constructing Atomic\nTungsten-Based Solid Frustrated-Lewis-Pair\nSites with d‑p Interactions for Selective CO<sub>2</sub> Photoreduction

Solid frustrated Lewis pair (FLP) shows remarkable advantages\nin\nthe activation of small molecules such as CO<sub>2</sub>, owing to\nthe strong orbital interactions between FLP sites and reactant molecules.\nHowever, most of the currently constructed FLP sites are randomly\ndistributed and easily reunited on the surface of catalysts, resulting\nin a low utilization rate of FLP sites. Herein, atomic tungsten-based\nFLP (N···W<sub>SA</sub> FLP) sites are constructed\nfor photocatalytic CO<sub>2</sub> conversion through introducing W\nsingle-atoms into polymeric carbon nitride. In the atomically dispersed\nN···W<sub>SA</sub> FLP, the electron-deficient W single-atom\nacts as the Lewis acid (LA), and the adjacent electron-rich N atom\nacts as the Lewis base. Through the combination of various characterizations,\nincluding pyridine-IR, in situ diffuse reflectance infrared Fourier\ntransform spectroscopy, CO<sub>2</sub>-temperature programmed desorption,\nand theoretical calculations, the positive effects of N···W<sub>SA</sub> FLP on photocatalytic CO<sub>2</sub> reduction are well\nrevealed. The N···W<sub>SA</sub> FLP can effectively\nadsorb CO<sub>2</sub> to form an unusual W–O–C–N\nstructure with significant d-p orbital interactions, which leads to\nan interesting “push–push” electron transfer\neffect. The π back-donation from W 5d to the antibonding orbital\n(2π) of CO<sub>2</sub> realizes reverse electron transfer from\nthe W single-atom to the O site, while the electrons are transferred\nfrom the electron-rich N site to the electropositive C site via Lewis\nacid–base interactions, therefore effectively breaking the\nCO bond to activate CO<sub>2</sub> molecules and boost CO<sub>2</sub>-to-CO performance. This work provides a brand new route for\nthe research on high-efficiency activation of small molecules based\non single-atom-based FLP catalysts.