Syntheses Of Novel Coordination Polymers Based On 4,6-bimidazide And Aromatic Carboxylic Acid And Its Catalytic Performance For CO Oxidation

Coordination polymers,also known as metal organic frameworks,have potential applications in catalysis,gas storage,selective adsorption and separation,optics and magnetism due to their structural diversity,controllable pore,high surface area and easy to functionalized.According to the principle of crystal engineering,for the purpose to investigate the coordination polymers based on pyridazine,the effects of synthesis conditions,metal centers and auxiliary ligands on the structure and properties of the products were studied.According to the structural characteristics of the as-prepared coordination polymer materials,we investigated their application in catalysis.The main results are as follows:?1?Under hydrothermal or solvent conditions,twelve new coordination polymers were successfully prepared by different metals reacted with bmp and auxiliary aromatic polycarboxylic acids.Compounds 1 and 2 are nickel and copper based coordination polymers prepared from terephthalic acid as the auxiliary ligands,respectively.1 bears the dia network with fivefold interpenetration and has better thermal stability.2 is a 3D coordination polymer with CdSO₄ topology.Compound 3is a 3D nickel based coordination polymer prepared by using isophthalic acid as the auxiliary ligand,it also is a CdSO₄ topology.Using 5-Nitroisophthalic acid as the auxiliary ligand,the isostructral 4 and 5 were obtained by employing nickel nitrate and cobalt nitrate as metal sources respectively,they possesses CdSO₄ topology and have good thermal stability.Under the similar conditions,using trimesic acid as the auxiliary ligand,6 with 1D chain structure was obtained,where two carboxyl groups of trimesic acid are unprotonated.By using 1,2,4,5-benzenetetracarboxylic acid as the auxiliary ligand,two isostructral 2D coordination polymers?7 and 8?were successfully prepared,their thermal stability temperature is above 360?.When using the larger aromatic polycarboxylic acid?3,3',4,4'-biphenyltetracarboxylic acid?as the auxiliary ligand,four coordination polymers?compounds 9-12?were obtained.Compounds 9 and 10 are isostructral 3D coordination polymers where the metal centers are zinc and cobalt and one carboxyl group of HBPTC3-is unprotonated,and their topology is a rare nbo-x-d/I m-3 m->I m m 2.11 is a 3D cadmium based coordination polymer with sqc111 topology,where the oxalate is derived from the in-situ oxidation of ethanol.Compound 12 is a copper based coordination polymer with the bilayer structure.?2?Several CuO-CeO₂ catalysts were prepared by using porous copper based coordination polymer?compound 2?as precursor.The catalysts were characterized by PXRD,TEM,Raman,H2-TPR,XPS and so on.And they were used to catalyze the oxidation of CO.The effects of the calcination temperature and the Cu/Ce ratio on the catalytic activity were investigated.The results showed that the catalysts prepared by using coordination polymer material as precursor could effectively inhibit the agglomeration of CuO and CeO₂,and they exhibited better dispersion.When the temperature rises to an appropriate temperature,there is strong interaction between CuO and CeO₂,which give more active interface between copper and cerium,and thus they showed the best catalytic activity for CO oxidation.With the increase of Cu/Ce ratio,the catalytic activity of CO firstly increased and then decreased.When the Cu/Ce ratio is 5:5,the reduced temperature moves towards the higher temperature,some highly dispersed copper oxide amasses and grew into larger particles,and thus the catalytic activity decreases.The reduced temperature of all Cu species of the catalysts was lower than that of pure CuO,indicating that the presence of CeO₂ could obviously promote the reduction of CuO.The CuCe600-3:7 shows the best catalytic activity,and the CO can be completely conversed at 85?,which resulting from the the more active species of CuO on surface of the catalyst and the high dispersion?3?A series of Co₃O₄-CeO₂ catalysts were prepared by the calcination method using different cobalt based coordination polymers as precursors.The catalysts were characterized by PXRD,XPS and so on,and applied to CO oxidation.The results showed that the Co₃O₄-CeO₂ catalyst prepared by using 6 as the precursor showed the best catalytic activity,which may be due to the better ability to activate CO.The effect of preparation conditions on the catalytic performance of Co₃O₄-CeO₂ catalysts was further investigated.It is found that the calcination temperature has a great influence on the growth and catalytic activity of Co₃O₄:the catalytic activity of CoCe?6?400-3:7 is lowest,while CoCe?6?500-3:7 is best,and CO could achieved100%conversion of at 140?,mainly resulting from its better activation ability for CO and higher surface area.The catalytic activity decreased with the increase of CeO₂ content,and the order of catalytic activity coincided with that of H₂-TPR and XPS.The introduction of CeO₂ improved the catalytic performance of Co₃O₄ for CO oxidation,which resulted in complete oxidation of CO at lower temperature.?4?Four Pd-loaded catalysts were prepared by immobilized Pd particles to four different nickel based coordination polymers with different structures and high thermal stability,and were further characterized by TEM,IR,PXRD,TG,BET and so on.The results showed that the structure of Pd-loaded samples remained intact after loading Pd.Pd nanoparticles were successfully loaded onto the supports.Of these,5-Pd catalyst were distributed uniformly on the carriers without agglomeration.XPS results show that the Pd nanoparticles exists in Pd⁰ form.The catalytic activity showed that the size of Pd nanoparticles is responsible for catalytic activity instead of the surface palladium content.Four Pd-loaded catalysts show certain catalytic activity for CO oxidation.Among them,5-Pd exhibits the best catalytic activity,and CO can be completely conversed at 180?.