Adsorption Electro-Neutralization of Ionic Liquids in Thorium-MOFs for Enhanced Photocatalytic CO2 Reduction

Abstract

Artificial photocatalytic CO2 conversion to energy fuels is highly sought due to the carbon-neutral plan. However, resolving the sluggish photogenerated charge separation and migration in photocatalysts remains a challenge. Herein, we present an adsorption electro-neutralization confinement strategy in ionic liquid (IL)-tailored thorium-based metal–organic frameworks (Th-MOFs) for boosting interfacial charge migration while integrating the merits of enhanced CO2 adsorption and activation by dual sites (Th-MOF and ILs). The introduction of ILs via adsorption electro-neutralization has prolonged the excited charge lifetime from 26.45 ps to an exceptionally high value of 293.70 ps and reduced the exciton binding energy from 88.11 to 72.06 meV. The surface potential distribution of the photocatalysts, obtained using in situ Kelvin probe force microscopy (KPFM), corroborates the enhanced surface charge migration. Consequently, 1-(4-bromobutyl)-3-methyl-imidazolium bromide ([BMIMBr]Br)-derived Th-MOF-[BMIMBr]Br delivers CO with a yield of 408.43 μmol g–1 h–1, being 1.5 times higher than the pristine Th-MOF (274.11 μmol g–1 h–1). Computational investigations revealed that the IL-Th-MOF can significantly lower the Gibbs free energy of the *COOH intermediate, which may account for the superior photocatalytic performance. This work expands the Th-based MOF chemistry and its applications in photocatalysis, providing a new strategy for enhancing surface charge transfer.