Cobalt-Based 3D Metal-Organic Frameworks: Useful Candidates for Olefin Epoxidation at Ambient Temperature by H2O2

Abstract

Two new 3D metal-organic frameworks (MOF), [Co(H-2-DHBDA)(bpe)](n) (1) and [Co(H-2-DHBDA)(bpee)](n) (2) [H-2-DHBDA = 2,5-dihydroxy-1,4-benzenediacetate, bpe = 1,2-bis(4-pyridyl)ethylene, bpee = 1,2-bis(4-pyridyl)ethane], were synthesized hydrothermally. Both compounds have a similar 3D structure. The secondary building unit is a Co-2 dimer with a CoCo distance of 4.02 angstrom. The hydroxy groups remain free on the surface of the compounds, and they participate in the intramolecular hydrogen bonding. A detailed structural analysis revealed that the structure is a 7-c uninodal net with the Schlafli symbol 3(3).4(13).5(4).6 and the vertex symbol [3.3.3.4.4.4.4.4.4.4.4.4.4.4.4.*.*.*.*.*.*]. The compound is catalytically active towards epoxidation reactions in heterogeneous medium with H2O2 as an oxidant. They catalyze the epoxidation of almost all types of olefinic substrates with good efficiency. After the reaction, the catalysts can be recovered quite easily, and they can be used for further reactions without any loss of activity for several cycles.