Mixed-Metal Metal–Organic Frameworks as Catalysts for Liquid-Phase Oxidation of Toluene and Cycloalkanes

A series of isostructural mixed-metal metal–organic frameworks (MM-MOFs) of 1,3,5-benzenetricarboxylate (BTC), M–Zn–BTC, where M = Cu(II), Co(II) and Fe(II) have been synthesized using the post-synthetic exchange method. The catalytic activities of the M–Zn–BTC have been investigated for the oxidation of toluene and cycloalkanes in the presence of hydrogen peroxide as oxidant. The M–Zn–BTC catalysts show improved activity and selectivity for toluene oxidation. The introduction of the second metal to the node of the MOFs improved the toluene conversion from 22 to 70% and the selectivity of benzaldehyde improved from 22 to 57%. The Fe–Zn–BTC showed the best activity in terms of benzaldehyde selectivity for the oxidation of toluene. However, Cu–BTC gave the highest conversion for cyclohexane and methylcyclohexane oxidation.