| In this paper,a series of new metal-organic frameworks(MOFs)constructed from double bond tetraacid ligands and nitrogen-containing heterocyclic polyacid ligands,with alkaline earth metal ions and transition metal ions have been synthesized and characterized under solvothermal conditions.The regulation of different factors on the structure and properties of MOFs was studied,and its topological structure,magnetic properties,fluorescence and ion recognition,adsorption properties,frontier molecular orbital theory,and Hirshfeld surface analysis were analyzed and discussed.2.Thirteen new MOFs based on 1,2-bis(5-isophthalate)ethylene(H4L1),namely,[Co(L1)]n(1),[Mn0.5(L1)0.5]n(2),[Sr(H2L1)(H2O)2]n(3),[Ca(H2L1)(H2O)2]n(4),[Mn(H2L1)(H2O)2]n(5),[Co(H2L1)(4,4?-bipy)0.5(H2O)]n(6),[Co(H2L1)1.5(1,10-phen)(H2O)2]n(7),[Ni(H2L1)1.5(1,10-phen)(H2O)2]n(8),{[Co(H2L1)(dib)]·2H2O}n(9),{[Ni(H2L1)(dib)]·2H2O}n(10),{[Ni(L1)0.5(bix)]·H2O}n(11),[Co(L1)(dpa)0.5(H2O)]n(12),[Ni(L1)(dpa)0.5(H2O)]n(13)have been prepared under the different synthesized conditions with alkaline earth metals Ca(II)and Sr(II),and transition metals Mn(II),Ni(II)and Co(II)in the presence or not of N-donor ancillary ligands(1,10-phen,4,4?-bipy,dib,bix and dpa).The magnetic test results show that the larger negative?values and the decrease of?MT with decreasing temperature in MOFs 1-2,7-8,and 11-12 all indicate that there is antiferromagnetic interaction between adjacent metal ions in the above-mentioned MOFs.The fluorescence test shows that the photoluminescence of MOFs 3-4 has a certain degree of blue shift compared with the free ligand.Among them,MOF 4 has unique optical properties and has a significant recognition effect on Fe3+,which can be used as choose a fluorescent probe that senses Fe3+.The study of PXRD and thermogravimetric analysis of MOFs shows that MOFs have better purity and higher stability.Further through DFT calculation and Hirshfeld surface analysis,it can be seen that MOFs are stable in the ground state,and there are a large number of short-range interactions in MOFs,which makes MOFs more stable.2.Five novel MOFs derived from the 2,4-[6-(4-carboxyphenyl)pyrazin-2-yl]benzoic acid(H2L2)ligand have been constructed under the different conditions with transition metal Co(II)and Ni(II)ions in the presence of N-donor ancillary ligands(4,4?-bipy and dib),namely,[Co2(L2)2(4,4?-bipy)]n(14),[Ni3(L2)2(4,4?-bipy)2(NO3-)2(H2O)4]n(15),[Ni(L2)(4,4?-bipy)0.5]n(16),{[Co(L2)(dib)0.5(H2O)2]·H2O}n(17),[Ni(L2)(dib)0.5(H2O)2]n(18).Through magnetic test analysis,there is antiferromagnetic coupling interaction between adjacent metal ions in MOFs14 and 18.The study of PXRD and thermogravimetric analysis of MOFs shows that the temperature at which the MOFs framework begins to collapse is around 400°C,indicating that these MOFs have good stability and high phase purity.Through DFT calculation and Hirshfeld surface analysis,it can be known that MOFs are stable in the ground state.3.Two rigid imidazole carboxylic acid ligands were designed and synthesized:2-(4-carboxy-phenyl)-1H-imidazole-4,5-dicarboxylic acid(H3L3),2-(3-carboxy-phenyl)-1H-imidazole-4,5-dicarboxylic acid(H3L4).Using the hydrothermal method to react with Cd(II)ions with the participation of auxiliary ligands to obtain two MOFs,namely,[Cd2(HL3)2(1,10-phen)2(H2O)2](19),{[Cd(L3)(dib)0.5(H2O)2]·2H2O}n(20).Since the cadmium ion with d10configuration has good luminescence properties,the fluorescence test of MOFs 19-20 was performed at room temperature,and it was found that compared with the free ligand H3L3,the fluorescence intensity of MOFs 19-20 was weakened and blue shift.The PXRD pattern shows that the purity of MOFs is high,and the crystal configuration does not change at room temperature.The TG curve shows that MOFs have good thermal stability.In addition,studies on the frontier molecular orbital theory of MOFs and Hirshfeld surface analysis show that the orbital energies occupied by the HOMO-LUMO of the obtained MOFs are all negative,indicating that MOFs are stable in the ground state,and there are a large number of short-range mutual The effect makes MOFs more stable. |
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