A Copper Metal-Organic Framework as an Efficient and Recyclable Catalyst for the Oxidative Cross-Dehydrogenative Coupling of Phenols and Formamides

A crystalline porous metal-organic framework Cu-2(BPDC)(2)(BPY) (BPDC=4,4-biphenyldicarboxylate, BPY=4,4-bipyridine) was synthesized and characterized by several techniques including XRD, SEM, TEM, thermogravimetric analysis, FTIR, atomic absorption spectrophotometry, hydrogen temperature-programmed reduction, and nitrogen physisorption measurements. The Cu-2(BPDC)(2)(BPY) could be employed as a heterogeneous catalyst for the copper-catalyzed cross-dehydrogenative coupling reaction of DMF with 2-substituted phenols to form organic carbamates through CH activation under oxidative conditions. The Cu-2(BPDC)(2)(BPY) offered higher catalytic activity than common copper salts such as Cu(OAc)(2), CuCl, CuCl2, CuI, and Cu(NO3)(2) as well as other Cu-MOFs such as Cu-3(BTC)(2), Cu(BDC), and Cu(BPDC). The Cu-2(BPDC)(2)(BPY) catalyst could be facilely separated from the reaction mixture, could be recovered and reused several times without significant degradation in catalytic activity.