Exploitation of missing linker in Zr-based metal-organic framework as the catalyst support for selective oxidation of benzyl alcohol

Abstract

Extensive studies have been done on the modification of the organic linkers with different functional groups for ameliorating the properties of Zr-based metal-organic frameworks (MOFs). In contrast, little effort has been devoted to Zr MOF modification at the –OH group arising from the incomplete coordination of Zr with the organic linkers. We focused on covalently immobilizing redox-active iron to the –OH group in the node of a Zr-based MOF for selective oxidation of benzyl alcohol to benzaldehyde, which is an important reaction in organic synthesis, pharmaceutical, and industrial areas. In this work, iron acetylacetonate was incorporated into Zr6(μ3-O)4(μ3-OH)4(HCOO)6(1,3,5-benzenetricarboxylate)2 or MOF-808. The air-stable Fe-anchored MOF-808 (Fe-MOF-808) was subjected to screening for the selective oxidation of benzyl alcohol to benzaldehyde. Fe-MOF-808 showed enhanced conversion and selectivity to benzaldehyde as well as catalytically outperforming the pristine MOF-808 in the reaction. The prepared solid catalyst also displayed the robustness without the leaching of the active site during the reaction, along with at least four-time recyclability of use without significant deactivation.