Poly‐Phosphamide Catalyzed Visible‐Light‐Driven CH₄ and Dark‐Phase‐Mediated Cyclic Carbonate Productions Utilizing CO₂

Abstract A poly‐phosphamide (POP) with a band gap of 2.8 eV is used for the photochemical conversion of CO₂ into CH₄ and chemical conversion of CO₂ and organo‐epoxides into cyclic carbonates. The Tauc plot and Mott Schottky analyses indicate the conduction band potential at −1.49 V (vs NHE), much more negative than the multi‐electron CO₂ reduction potential and the lifetime of the photo‐excited electron is found 2.8 ns. On photoirradiation of 420 nm light, the POP in the presence of triethanolamine or ascorbic acid can selectively convert CO₂ into CH₄ (≈99%) with a yield of 4.6 mmol g⁻¹. On visible‐light irradiation, the drop of charge‐transfer resistance (R_ct) and an enhancement of cathodic current further confirm the photon‐harvesting efficiency of the POP. In situ, FTIR study identifies the CO₂ adsorption to the POP and possible reaction intermediate, like *‐CO, *‐CH₂OH. POP also behaves as a catalyst for CO₂ conversion to cyclic carbonates under solvent‐free conditions with more than 98% yield. After the light‐phase and dark‐phase reactions, POP can be successfully recycled at least five times without structural degradation. Herein, the POP acts as a bi‐functional, and recyclable polymeric organic material to convert CO₂ to essential feedstocks under mild reaction conditions.