| With the rapid development of crystal engineering and material chemistry,metal-organic frameworks(MOFs)have received extensive attention in the field of proton conduction due to their adjustable structures,high crystallinity,porosity,and rich hydrogen bonds.Since N-heterocyclic carboxylate ligands have the advantages of strong coordination ability,variable coordination modes and can be used as proton sources,the research on the proton conductivities of MOFs constructed by such ligands is a recent hotspot.Five N-heterocyclic carboxylate ligands,2-(2-carboxyl phenyl)-4,5-imidazole dicarboxylic acid(o-CPhH2IDC),2-(4-pyridyl)-4,5-imidazole dicarboxylic acid(4-H3PyIDC),2-(3-pyridyl)-4,5-imidazole dicarboxylic acid(3-H3PyIDC),4-(2,4,6-tricarboxyphenyl)-2,2 ',6 ',2 ' '-terpyridine(H3tpt),3,4-bis-[1,2,4]triazole-1-methyl-thieno[2,3-b]thiophene-2,5-dicarboxylic acid(H2ttc)were selected to prepare nine MOFs and one HOF,1D {[Cd(o-CPhH2IDC)(4,4 '-bipy)0.5(H2O)2]·3H2O}n(1),0D {[Cd2(o-CPhH2IDC)2(H2O)6]·4H2O}n(2),3D[Ba(o-CPhH2IDC)]n(3),3D[Cd(4-HPyIDC)(H2O)]n(4),1D[Mn(3-HPyIDC)(H2O)2]n(5),3D {[(H3tpt)]·4H2O}n(6),1D {[Cu(H2tpt)Cl]·CH3OH}n(7),1D {[Cu(H2tpt)(H2O)]·1/2SO4·2H2O}n(8),0D {[Ni(H2tpt)2]·3H2O}(9),3D{[Co2(ttc)2(H2O)]·2DMF·4H2O}n(10).Firstly,their molecular structures were determined by powder X-ray diffraction(PXRD)or single crystal X-ray diffraction(SXRD),infrared(IR),elemental analysis(EA)and so on.Then,thermal analysis(TG),scanning electron microscope(SEM),PXRD and other methods were used to confirm their thermal stability,water stability and chemical stability.N2 saturated adsorption and BET surface areas were determined by N2 adsorption and desorption tests,and the water vapor saturated adsorption of these compounds was determined as well.Then,the AC impedance tests for temperature and humidity gradients of 1-10 were carried out to obtain their proton conductivity under 68%-98%RHs and 30-100?.The results show that the conductivity of 1-10 increases with the increase of temperature and humidity.They are typical temperature and humidity dependent proton conductors,and the highest proton conductivity almost reaches more than 10-4 S·cm-1.Their optimal conductivities are as follows:2,87 × 10-4 S·cm-1,1.68 × 10-4 S·cm-1,3.08 × 10-4 S·cm-1,0.78 × 10-4 S·cm-1,1.49 × 10-4 S·cm-1,5.32 × 10-4 S·cm-1(98%RH,80?,3.65 × 10-4 S·cm-1,4.23 × 10-4 S·cm-1,4.00 × 10-4 S·cm-1,1.97×10-4 S·cm-1.Obviously,a large number of free carboxyl groups and hydrogen bond networks exist in the frameworks,which consisted of coordination water molecules or lattice water molecules,and are very conducive to the protons,so that they have good proton conductivities.It should be emphasized that the three-dimensional HOF 6 was prepared through solvothermal method,which can not only be stable in water solutions,but also in acid solutions.It is a highly stable crystalline material.Through the AC impedance test,it is found that 6 is also a typical temperature-and humidity-dependent proton conductor.Under 80? and 98%RH,the optimal proton conductivity can reach 5.32× 10-4 S·cm-1.It provides a new idea for the design of proton conductors with excellent performance. |
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