Theoretical And Experimental Studies On Common Carboxylic Acids And Nitrogen-containing Ligands For Metal-organic Framework Compounds

The design and syntheses of metal organic frameworks(MOFs)have attracted growing research interest not ony because of their intriguing aesthetic architectures,but also owing to their promising applications in gas storage and separate,catalysis and sensing.But the water and thermal stability of MOFs limits their applications.The thesis is divided into four chapters.The introduction includes the MOFs definition,syntheses,synthetic factors,applications,hydrothermal stability and the developments in their theoretical calculations.And in chapter one,we also summarize the developments of MOFs based on the pyridine and pyrimidine ligands.In the second chapter,we use the Gaussian 09 program to calculate the pKa and NBO charges of 31 carboxylic acids ligands and 27 nitrogen heterocyclic ligands.Based on the calculation results and the strength and polarity of M-L,we successfully explain the experimental results of the hydrothermal stability of some of the MOF materials.Our calculation results not only can be used to choose suitable ligands to synthesize stable MOFs,but also can give some guidance to their synthetic procedure.In the third chapter,we synthesized two rigid tetrahedral polydentate nitrogen heterocyclic ligands,the TMPM and TPPM.According to our calculated results,we find the NBO charges of the former coordination atom is larger than that the later,which is consistent with the fact that all our effort to obtain MOFs with TPPM is unproductive.We used the TMPM to assemble with Mn(II),Co(Ⅱ)and Cu(Ⅱ)and obtained three 3D complexes {[(MnCl2)2(TMPM)](CH3CN)3}n(1),{[CoCl2(TMPM)](H20)}n(2)and{[CuCl2(TMPM)](DMF)2}n(3).The compound 1 is a new topological structure,and 2 and 3 are isomorphous.Since complex 1 is unstable,we did not study its property.We studied the hydrothermal stability of complexes 2 and 3.We found both 2 and 3 are stable in water.Comparing their thermal stability,the order is 2>3>1.The order of the stability is consistent with the order we proposed based on the charges and radius of metal ions assuming the coordination are to the same ligand and in the same manner.The order we proposed provides a guidance for the syntheses of stable MOFs.In the last chapter,we give a summary of the main findings of the thesis and prospects for future studies.