Catalytic Effect of Pd NPs Encapsulated in UiO-66(Zr) under Microenvironment Modulation for the Degradation of Trimethoprim in Fenton-like Reaction.

The large-scale production of iron sludge and the safety issues of HO usage are two limitations in the promotion and application of the Fenton reaction. To further solve the problems, an active hydrogen reduction strategy was proposed. Herein, the reducing property of active hydrogen was utilized to simultaneously generate HO in situ and accelerate the regeneration of ferric in the reaction process. The composite metal-organic frameworks (MOFs) Pd@UiO-66(Zr) and Pd@UiO-66(Zr)-2OH, which were stable under acidic conditions, were synthesized for hydrogen activation. Under the condition of only trace amounts of ferrous and hydrogen added, both catalysts showed excellent performance in the degradation experiments of trimethoprim. The of the Pd@UiO(Zr)-66-mediated system is 0.0487 min, which is 1.67 times that of Pd@UiO-66(Zr)-2OH. In the pollutant degradation reaction system constructed by these two materials, both of the hydroxyl radicals and singlet oxygen play a dominant role. The Bader charge analysis showed that the charge transfer from Pd to the MOF host was higher on Pd@UiO-66(Zr) than Pd@UiO-66(Zr)-2OH, which could be a key factor in distinguishing the catalytic activity of the catalysts. In addition, both catalysts showed excellent stability over six cycles. Nearly 100% degradation of trimethoprim could be achieved. This study provides some reference for the control of emerging pollutants by UiO-66(Zr) series materials.