Engineering a polyoxometalate-based metal organic framework with more exposed active edge sites of Ag for visible light-driven selective oxidation of cis-cyclooctene

Abstract

Epoxides are an extremely important class of chemical intermediates in the chemical industry due to the versatility of epoxides in preparing many fine and specialty chemicals. However, designing more active and selective heterogeneous catalysts in epoxidation is still a priority and a challenge. In this work, we demonstrate the synthesis of two new Ag/polyoxometalate-based coordination polymers (Ag₈(mttz)₄(H₂O)[PW^VW^VI₁₁O₄₀]·H₂O (1) and Ag₈(mttz)₄(H₂O)[PMo^VMo^VI₁₁O₄₀] (2), mttz = 5-methylthio-2H-tetrazole) that are highly active for the selective oxidation of cis-cyclooctene to epoxycyclooctane under mild conditions (solvent-free, atmospheric pressure, 70 °C with H₂O₂ as the oxidant under visible light). It is worth noting that compound 1 possesses abundant exposed active edge sites of Ag, resulting in the catalytic performance achieved in the selective oxidation of cis-cyclooctene to epoxycyclooctane being superior to its components (metal, polyoxometalates and ligand) and compound 2 with the conversion/selectivity to epoxycyclooctane of 70.15/99.68%, respectively. The excellent photocatalytic activity of compound 1 should be attributed to the synergy of the components after coordination polymerization and its structure with exposed active edge sites of Ag.