Visible-Light-Driven Photoreduction of CO₂ to CH₄ over N,O,P-Containing Covalent Organic Polymer Submicrospheres

Solar-energy-driven photoreduction of CO₂ to hydrocarbon fuels is an interesting and challenging topic, which generally requires photocatalysts with the capability to capture and photoreduce CO₂ simultaneously. Herein, we demonstrate that a N,O,P-containing covalent organic polymer (NOP-COP) prepared via condensation of hexachlorocyclotriphosphazene with barbituric acid can capture CO₂ and further photocatalyze its reduction to CH₄ under visible-light irradiation. The characterization information indicates that the incorporation of phosphorus in the skeleton of NOP-COP promoted the absorption of visible light and improved the lifetime of the photoinduced carriers. As a result, NOP-COP exhibited enhanced efficiency for photoreduction of CO₂ compared with the N,O-containing polymer, affording CH₄ as the sole carbonaceous product with a rate of 22.5 μmol g_cat^-1 h^-1 and selectivity over 90%. This work provides insight into designing and fabricating polymeric photocatalysts for CO₂ photoreduction to fuels.