Selective oxidation of phosphonates to phosphates via direct photolytic cleavage of C-P bonds on BiOCl driven by...

Phosphonates, possessing stable carbon-phosphorus (C-P) bonds and strong complexing capability, pose significant challenges in total phosphorus control during wastewater treatment. Herein, we demonstrate an ultrafast and highly selective C-P bond cleavage strategy for phosphonate degradation through interfacial complexation in the UV/BiOCl system. This approach achieved 86.54 % conversion of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) to orthophosphate within 10 min, exhibiting steady efficiency over pH 4-10 despite high salinity (Cl⁻) and organic matter (TOC). XRD and Raman analyses revealed that the selective HEDP oxidation is coupled with surface phase transition and chemical coordination environment changes, primarily characterized by the reduction of Bi³⁺ to Bi⁰. Furthermore, XPS and UV-Vis DRS results demonstrated that the HEDP-BiOCl surface complexation structure mediated a unique interfacial phase transformation mechanism, distinct from conventional photocatalytic radical-based pathways. ICOHP calculations showed that HEDP preferentially forms strong Bi-O(P) coordination bonds (2.31 Å) on BiOCl(110) surface. This interfacial complexation weakens specific C-P bonds and promotes UV-induced ligand-to-metal charge transfer (LMCT), which results in photolytic C-P bond cleavage. LC-MS measurements identified the primary intermediate products to elucidate direct phosphonate-to-phosphate conversion (72.67 %) within the initial 2 min, confirming the targeted HEDP oxidation pathway. This interfacial complexation strategy provides molecular-level insights into C-P bond activation and a promising approach for phosphonate remediation in wastewater treatment, tackling environmental risks associated with organophosphorus pollutants.