Actinyl-Modified g-C3N4 as CO2 Activation Materials for Chemical Conversion and Environmental Remedy via an Artificial Photosynthetic Route.

Abstract

With the reported CO2 activation for the oxidation of benzene to phenol (-ENE → -OL) by the graphitic carbon nitride g-C3N4 (CN) via an artificial photosynthetic route as inspiration, high-valent actinyls (AnmO2)n+ (An = U, Np, Pu; m = VI, V; n = 2, 1) have been introduced for its further modification. Our calculations indicate thermodynamic spontaneity in the feasibility of g-C3N4-(AnmO2)n+ (CN-Anm) formation. The magnificent structural and electronic properties of CN-Anm are utilized for CO2 activation in terms of the rarely studied -ENE → -OL conversion. The calculated free energies show that most steps of the catalytic cycle are favored by CN-Anm complexes. The first step (carbamate formation) is slightly endothermic in all cases, where CN-U is 0.51 eV higher than CN and CN-Pu is -0.01 eV lower. All benzene addition reactions release energy, with that for CN-U being the lowest. The phenolate formation is favored by some actinyl complexes over CN, and CN-U is only 0.23 eV higher. The phenol release (resulting in formamide complexes) and CO desorption are exothermic for all CN-Anm. The overall process suggests the improved catalytic performance of actinyl-modified CN materials, and the slightly depleted uranyl-carbon nitride could be one of the promising catalysts.