The Synthesis,Structures And Proton Conductivity Properties Of 3,6-Carbazole Dicarboxylic Acid Based MOFs

Solid-state proton conductive materials have become hotspot for their wide range application.MOFs materials have become new proton-conducting materials for their regular arrangement,high crystallinity,and the controllability of guest molecules.The anion-framework carboxylic acid-based In3+-MOFs materials will features of[(CH3)2NH2]+cations present in the pores,which will promote proton conductivity.The 3,6-carbazole dicarboxylic acid is the linker which characterized as an angle of 90° between the planes of carboxylic groups.In this research,a series of In(?)carboxylate based MOFs were synthesized by choosing 3,6-carbazole dicarboxylic acid as the first ligand and the effect of structural differences on the proton conductivity properties was investigated.First,three ligands with different structures(4,4'-bibenzonic acid,1,4-benzene dicarboxylic acid,1,4-cyclohexane dicarboxylic acid)were chosen to participate the construction of In3+-MOFs,for regulating the proton conductivity of mono-ligand-In3+-MOFs.The participation of the second ligand does not change the manner in which the mononuclear metal indium cheats to the carboxyl group but changes the structure which converts double-interpenetrating three-dimensional structure to the two-dimensional layered structure.Among them,The BDC participated In3+-MOFs exhibit the best proton conductivity properties with the highest conductivity value of 9.72×10-4 S cm-1,under anhydrous conditions;and that value of BPDC participated In3+-MOFs following but higher that of Vono-ligand-In3+-MOFs.The ligand CHD participation makes a negative effect on the proton conductivity.Secondly,the ligand 1,3,5-benzenetricarboxylic acid was chosen to participate in the construction of In3+-MOFs.But the chiral mono-ligand-In3+-MOFs(MROF-30)magically got with outstanding structural features as follows.1)There is a rare triple helix metal oxygen chain with a pitch of 21.370 A and a screw hole diameter of 10.7713 A;2)The metal-organic linker bridged helical chains to construct the pioneer 3D framework,with a pore size of 44.276 A,which is the largest among reported In3+-MOFs.Next,the method coating mixing matrix was proposed to improve the humidity stability of MROF-30.The prepared films have a high proton conductivity of up to 4.62 ×10-2 S cm-1 at 70 ? and 90%RH,and more importantly,the framework of the MROF-30 remains.