Multi-pathway and multiple-mechanism in action together: High-efficient visible-light photocatalytic oxidation and hydrolysis of CEES by a ligand-differentiated Zr-MOF

Abstract

It is always important to develop materials that are capable of fast catalytically degrading sulfur mustard (HD) by selective oxidation and/or hydrolysis to its nontoxic form. In this paper, ligand-defected UiO-66-NH₂ is firstly prepared using acetic acid as a coordinating modifier, and then 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin molecules are introduced by coordination and amidation reactions to form a new ligand-differentiated MOF UiO-66-NH-AA −TCPP. The new MOF achieves round-the-clock degradation of 2-chloroethyl ethyl sulfide (CEES, HD simulant) by visible-light photocatalytic oxidation and hydrolysis. Notably, the MOF degrades 97.8 % of CEES within 1 h with a half-life of 9.12 min via the cooperation of oxidation and hydrolysis. It is demonstrated that while TCPP increases the number of photoexcited electrons by enhancing visible-light absorption, the electron push–pull effect between –NH₂ and –COOH groups of TCPP through the coordination reaction facilitates electron transfer along the ligand–metal cluster–ligand direction, which improves photocatalytic yield of ¹O₂ for selective oxidation of CEES to sulfoxide. Meanwhile, the MOF shows a stronger ability to hydrolyze CEES than UiO-66-NH₂ due to the lipophilicity of porphyrin increasing the contact with CEES. Noteworthily, it is concluded that the MOF achieves efficient decontamination of CEES through a multi-pathway and multi-mechanism co-action strategy.