H2O as intermediate medium achieve the photocatalytic conversion of methane and carbon dioxide

Methane (CH 4 ) and carbon dioxide (CO 2 ) are the most prominent greenhouse gases. Their simultaneous photocatalytic conversion presents an effective strategy for advancing sustainable chemical transformations. In this study, a nanocomposite photocatalyst composed of Keggin-type phosphomolybdate (CsNiPMO) and TiO 2 nanosheets was synthesized to enable the co-conversion of CH 4 and CO 2 at room temperature. Specifically, CH 4 was oxidized to form formaldehyde (HCHO), while CO 2 was reduced to CH 4 . The formaldehyde yield reached 4284 μmol·g −1 ·h −1 , with a selectivity of 98.3 %. Mechanistic investigations revealed that water serves as a crucial intermediate medium. Hydroxyl radicals (·OH), generated via water oxidation, were identified as the primary active oxygen species responsible for CH 4 oxidation. Additionally, the hydrogen ions (H + ) generated during water oxidation served as the hydrogen source for the CO 2 reduction. The introduction of CsNiPMO has facilitated the efficient charge separation within TiO 2 , enabling spatially separated redox reactions: CO 2 reduction occurred predominantly on CsNiPMO, while CH 4 oxidation was confined to TiO 2 nanosheets. This work demonstrates a highly efficient photocatalytic system for selective CH 4 oxidation and CO 2 reduction under mild conditions, providing a novel and sustainable approach for the high-selectivity conversion of methane.