Construction Of Triphenylamine-Based Metal-Organic Coordination Polymers And Their Application In Catalysis

Metal-organic coordination polymers,as a new type of inorganic-organic hybrid materials,have special advantages of capture,sequestration and conversion of small-molecule gases due to their intrinsic nature of large surface area and high porosity.Triphenylamine molecules usually possess structural rigidity,good chemical stability,excellent photoactivity and can be easily modified.We introduced polar groups,thiophene moieties or pyridyl rings into the backbones of triphenylamine(TPA)molecules to gain materials with large cavity,strong adsorption and photoactive properties which contribute to carbon dioxide(CO2)capture and conversion.In this dissertation,a series of ligands with large size,visible light absorption performance or multi-coordination modes were synthesized.We constructed a series of porous metal-organic coordination polymer catalysts through the assembly of the as-synthesized ligands and the active transition metals.These catalysts possess large pore channels,photocatalysis activity or strong CO2 activation property,which can achieve the combination of CO2 capture and conversion in one pot,i.e.,the direct trifluoromethylation of aromatic heterocyclic compounds and trifluoromethyl free radical-assisted CO2 reduction.Enlightened by the unique promotiorn of acylamide groups on CO2 adsorption,we proposed a new way of extending the TPA ligand by introducing para-amino carboxylic benzene moieties.Two metal-organic coordination polymers,Zn-NTTA and Cu-NTTA with(3,28)and(3,24)connected units,were successfully synthesized consequently.The high uptake of CO2(115.6 cm3·g-1)and selectivity over N2(30:1)at 273 K indicates that Cu-NTTA is an excellent candidate for post-combustion CO2 isolation and capture.Zn-NTTA exhibited high catalytic activity,rapid transformation dynamics and excellent stability in the cycloaddition of carbon dioxide with epoxides.The combination of the selective capture and catalytic transformation in one-pot enables the direct use of raw power plant flue gas without further separation and purification.The construction of layered porous coordination polymer Zn-TCTA with visible light harvesting ability(400-600 nm)used for direct trifluoromethylation without pre-functionalization of the aryl precursors was achieved by enlarging the ?-system of a triphenylamine-based ligand through the incorporation of thiophenes.The X-ray diffraction results manifests well-defined non-covalent interaction between the pores and adsorbed substrates.This interaction provides the possibilities of enhancing the oxidation of the radical adduct in the pores of Zn-TCTA and preventing over trifluoromethylation of products.A photoactive ligand H2SPyTCA with pyridine and carboxylic acid coordination groups was synthesized based on the above research on photocatalytic trifluoromethylation.The incorporation of H2SPyTCA and Zn2+ ions obtained a coordination polymer Zn-SPyTCA-1 with large one-dimension hexagonal channels(the side length,13.4 A).The effective pore volume was 31587 A3,and the porosity was 77.5%.Combining Zn-SPyTCA-1(photosensitizer)with cobaltoximes catalyst,new types of heterogeneous catalytic systems have been developed.The coupling reaction of photocatalytic hydrogenation and oxidation of benzyl alcohol showed that Zn-SPyTCA-1 possessed good stability and photoactivity.The photocatalytic radical-assisted reduction of CO2 was achieved through the synergistic effect between the photosensitizer and the catalyst by lowering the activation energy of CO2.