Elucidating the charge redistribution in bimetallic metal–organic frameworks: High-electron-density reactive center for removal of organic micropollutants in water

For the elimination of pharmaceutical and personal care products (PPCPs) from water, various methods and materials have been designed, while the removal effect of PPCPs is still mediocre due to the limitation of trace concentration. Therefore, constructing high-electron-density reactive centers (HRCs) for effective processing is urgent due to the potential threat to human health posed by PPCPs in water. Herein, a bimetallic metal–organic framework (BMOF-Ti/Zr6%) was synthesized by a solvothermal method with enhanced adsorption and photocatalytic capacity to address the issue. The Zr doping in metal clusters elevated the adsorption capacity of 2,2′,4,4′-tetrehydroxybenzophenone (BP-2) on BMOF-Ti/Zr6% to 4032 μmol/g, and the photocatalytic rate was more than 6 times higher than that of the pristine metal–organic framework. The enhanced adsorption and photodegradation of PPCPs on BMOFs was ascribed to the charge redistribution between Ti and Zr inducing the formation of HRCs. The electrons accumulated on HRCs altered the adsorption performance of metal sites and facilitated the generation of reactive oxygen species, which was further confirmed by theoretical calculations and indirectly validated by the interface behaviors of dissolved organic matter (DOM). Moreover, the possible reaction pathway of BP-2 degradation was explored. In addition, the BMOF-Ti/Zr6% retained more than 90% of initial adsorption capacity in photocatalytic regeneration experiments, demonstrating the potential for application in natural water matrix. These findings reinforce the understanding of charge behaviors in bimetallic materials and contribute to understand the impact of DOM in water remediation processes.