Mechanism of condensed-phosphate recovery based on an electrocatalytic coupling adsorption system using metal–organic framework–derived Mg/O dual-vacancy MgO

Phosphate ore reserves are insufficient for sustained human use, and the resource recovery of condensed phosphates in water bodies remains challenging. Herein, nanomagnesia (AA-MgO) with coexisting magnesium and oxygen vacancies was synthesized via the sacrificial template method using metal–organic frameworks. AA-MgO achieved efficient condensed-phosphate catalysis and simultaneous orthophosphate recovery in an electrocatalytic coupling adsorption system. Its unique dual-vacancy structure considerably enhanced its electrocatalytic performance. Under optimal conditions, AA-MgO showed adenosine triphosphate (ATP) and pyrophosphate (P ∼ P) removal rates of 98.75% and 98.20%, respectively, exhibiting 2.06–13.23 times better pseudo-first-order kinetics than commercially available MgO. After being regenerated thrice, AA-MgO maintained a > 70% removal rate, demonstrating excellent structural stability. Quenching and radical-trapping experiments confirmed that the catalytic process involved radical and nonradical pathways, with ·OH playing a dominant role in catalyzing ATP, while the nonradical pathway involving 1 O₂ contributed more significantly to P ∼ P degradation. Density functional theory calculations showed that the ATP adsorption energy was higher on the V Mg  + V o surface than on the V o surface. Moreover, the energy barrier of the rate-determining step in P ∼ P degradation was lower on the former, indicating that this surface favored condensed-phosphate degradation. Finally, differential charge and electrochemical characterization revealed that AA-MgO exhibited superior electron transfer rates than MgO.