Ruddlesden-Popper La2CoO4 with Surface Hydroxyl Engineering for Efficient Catalytic Hydrolysis of Organophosphate Esters and In Situ Phosphate Immobilization.

Organophosphate esters (OPEs) are persistent emerging contaminants whose hydrolysis is kinetically limited under environmentally relevant conditions, while the released phosphate poses a potential risk of secondary phosphorus pollution. Current catalytic strategies predominantly attribute organophosphate hydrolysis to Lewis acid activation, whereas the contribution of surface hydroxyls remains poorly understood. Herein, fuel chemistry was tuned during solution combustion synthesis to systematically tailor the surface hydroxyl abundance of Ruddlesden-Popper La2CoO4 and elucidate its role in organophosphate hydrolysis. Using p-nitrophenyl phosphate (p-NPP) as a model substrate, the optimized glycine-derived La2CoO4 catalyst (Gly-LCO) achieved a hydrolysis rate constant of 0.30 h-1 under neutral conditions, which was 6.1 and 15.8 times that of benchmark La2O3 and La(OH)3, respectively. Meanwhile, the released phosphate was effectively immobilized through stable La-O-P coordination, suppressing secondary phosphorus release. Spectroscopic characterization and density functional theory (DFT) calculations revealed that abundant surface hydroxyls enhance substrate adsorption, induce interfacial electron redistribution, and accelerate P-O bond cleavage. These findings identify surface hydroxyls as key regulators governing the coupling of organophosphate hydrolysis and phosphate immobilization, providing mechanistic insight into the design of multifunctional lanthanum-based catalysts for contaminant transformation and phosphorus management in aquatic environments.