Ultrathin cerium phenylphosphonate nanosheets for photocatalytic cycloaddition of carbon dioxide to epoxides

2D cerium phenylphosphonate nanosheets were prepared through a facile hydrothermal procedure. Analysis revealed the monoclinic phase of cerium(IV)-bis(phenylphosphonate) with an ultrathin sheet like morphology and +3 and +4 oxidation states of cerium. Notably, the nanosheets exhibited light absorption at around 325 nm, suggesting a band gap value of 3.0 eV. Mott-Schottky analysis provided additional insight, revealing a CB position at -0.123 V_RHE and a VB position at 2.877 V_RHE. The photocurrent analysis and Nyquist plots demonstrated the nanosheets' ability to generate photoelectrons when exposed to light and effectively separate holes and electrons. The catalytic efficiency of the nanosheets was evaluated in a cycloaddition reaction involving several epoxides and CO₂, resulting in the production of five-membered cyclic carbonates. Remarkably, in a solvent-free environment, the nanosheets achieved a product yield of over 90%. A series of meticulously controlled experiments were conducted to elucidate the mechanism, revealing that the reaction proceeds through a radical pathway. These findings indicate that these nanosheets can act as a highly efficient catalyst for the CO₂ fixation reaction, displaying high yield and recyclability.