Effective Combination of the Metal Centers in MOF-Based Materials toward Sustainable Oxidation Catalysts

Abstract

A successful encapsulation of Keggin-type polyoxomolybdate (H3[PMo12O40], PMo12) into metal-organic framework (MOF) materials with an identical framework but distinct metal centers (ZIF-8 with Zn2+ and ZIF-67 with Co2+) was accomplished by a straightforward room-temperature procedure. The presence of Zn2+ in the composite material PMo12@ZIF-8 instead of Co2+ in PMo12@ZIF-67 caused a remarkable increase in the catalytic activity that achieved a total oxidative desulfurization of a multicomponent model diesel under moderate and friendly conditions (oxidant: H2O2 and solvent: ionic liquid, IL). Interestingly, the parent ZIF-8-based composite with the Keggin-type polyoxotungstate (H3[PW12O40], PW12), PW12@ZIF-8, did not show the relevant catalytic activity. The ZIF-type supports present an appropriate framework to accommodate active polyoxometalates (POMs) into their cavities without leaching, but the nature of the metallic center from the POM and the metal present in the ZIF framework were vital for the catalytic performance of the composite materials.