Construction And Properties Of Metal-organic Coordination Polymers Based On N-containing Carboxylic Ligands

Metal-organic coordination polymers are a new kind of crystalline materials which are built by organic ligands and metal ions.They have attracted a great deal of attention not only because of their various structures and excellent properties derived from the variety of organic ligands and the rich coordination modes of the metal ions,but also for their potential applications in gas adsorption and separation,photoelectromagnetic,catalysis,the storage and drug delivery.In this paper,8 new coordination polymers materials have been constructed by hydrothermal and solvothermal methods,further more,we characterized their structures,explored their properties,and obtained some valuable conclusions.The main contents are as follows:(1)Based on the 5,5-(quinoxaline-5,8-diyl)-diisophthalate(H4L1),two novel three-dimensional(3D)porous coordination polymers(WN-1)and(WN-2)have been synthesized by solvothermal methods,and tested in catalytic reduction of p-nitrophenol.The obtained MOF(WN-1)is inert in the title reaction.A new type of Co-based catalyst(CoOx@CN)was prepared via thermal treating WN-1 under mild condition.The CoOx particles about 3-5 nm homogeneously embedded in the carbon matrix.The catalytic activity of the obtained catalyst(the substrate can be almost completely transformed within only 10 mins)was higher than that of cobalt oxide(the conversion of p-nitrophenol is 10% in 40 min reaction)and carbon supported cobalt oxide catalyst(the conversion of p-nitrophenol is 2% in 40 min reaction)in the hydrogenation of p-nitrophenol.Compared with the traditional Co-based catalysts,CoOx@CN,which wasobtained by fine-thermal treating coordination polymers(WN-1),showed higher catalytic activity in reduction process.(2)Four new metal-organic coordination polymers(WN-3 — WN-6)have been synthesized by hydrothermal and solvothermal methods based on the 6-(3-pyridyl)isophthalic acid(H2pip).With the help of the auxiliary ligands,we obtained three different crystal structures under similar conditions(WN-3 reveals a 0D mononuclear structure,WN-4 has a 2D layer structure while WN-5 displays a 3D network structure).Notably,WN-4 and WN-5 reveal high thermal(remain stable in boiling water for72 h)and aqueous stability(remain stable even in ethanol for72 h),suggested by TGA and PXRD data.Moreover,the magnetic measurements indicate WN-4 and WN-5 are both exhibit antiferromagnetic behavior.(3)Based on the 2-(pyridin-4-yl)terephthalic acid(H2pta),which is similar to H2 pip,two novel three-dimensional(3D)porous coordination polymers(WN-7)and(WN-8)have been synthesized by solvothermal methods.Both of them have bigger pore sizes,52.8% and 35.4%,respectively,which could be further explored for their adsorption properties.