Synthesis of Asymmetrical Organic Carbonates Catalyzed by Metal Organic Frameworks

Metal organic frameworks (MOFs) are a new class of materials that are formed by the copolymerization of organic ligands with transition metals.Because of their properties such as high surface areas,microporosity,and the ability to tune pore size,many applications have recently been developed in catalysis,separation,and gas storage.We prepared MOFs by three different methods and characterized them with scanning electron microscopy (SEM),X-ray diffraction (XRD),and infrared (IR) spectroscopy.MOFs prepared via the three methods are completely different in morphology and microstructure.We demonstrate that the MOFs prepared via the "direct mixing" method are very effective heterogeneous catalyst for the transesterification of diethyl carbonate with alcohols to prepare organic carbonates.We studied the effects of the amount of MOFs,the reaction time,and the reaction temperature on product yield.Asymmetric organic carbonates can be produced with moderate to high yields and 100% selectivity via the reaction of diethyl carbonate with aromatic,cyclic,heterocyclic,or aliphatic alcohols.The solid catalyst can be recovered simply by centrifugation and reused for at least two cycles.