The Potential Application Research Of Electrode Materials Based On Bis(imidazole) Cd-MOFs Precursors In Supercapacitors

Metal-organic frameworks(MOFs)have emerged as a new kind of multifunctional materials that not only possess many advantages,such as highly ordered architectures,large specific surfaces and tunable pore sizes,but also can be used as precursors to prepare porous materials,which is attracting considerable attention in many fields such as gas absorption,optical,magnetic and supercapacitors.In this paper,nine new cadmium metal-organic frameworks(Cd-MOFs),have been constructed from the reactions of Cd(NO3)2·4H2O with 1,4-benzenedicarboxylate(p-H2bdc),1,3-benzenedicarboxylate(m-H2bdc)and structure-related bis(imidazole)ligands(1,4-bis(imidazol-1-yl)-benzene(bib),1,4-bis(benzoimidazol-1-yl)-benzene(bbib),4,4'-bis(imidazol-1-yl)-biphenyl(bibp)and 4,4'-bis(benzoimidazol-1-yl)-biphenyl(bbibp))under solvothermal conditions.Considering the pore-forming effect of cadmium vapor,as the first time,we utilized these Cd-MOFs as precursors to further prepare porous carbon materials(PCs)through the calcination-thermolysis procedure,which show different porous features corresponding to the topological structures of Cd-MOFs.Furthermore,the as-synthesized PCs were processed with KOH to obtain activated porous carbon materials(APCs)with higher specific surface area and porosity,which greatly promote the energy storage.It has potential applications in supercapacitors.The main contents have been summarized as following:1.Four new Cd-MOFs 1-4 with different bis(imidazole)ligands have been synthesized under solvothermal conditions.The structural diversity indicates that the backbone of bis(imidazole)-ligand(including the terminal group and spacer)plays a crucial role in the assembly of mixed-ligand frameworks.Significantly,it is found that the specific surface area and capacitance of PC are tuned by the Cd/C ratio of MOF.After being fully characterized,we found that APC-bib displays the largest specific surface area(1290 m2 g-1)and total pore volume(1.37 cm3 g-1)among the series of carbon materials.Consequently,APC-bib demonstrates the highest specific capacitance of 164 F g-1 at the current density of 0.5 A g-1.2.New Cd-MOFs 5-9 with different topology structure have been synthesized under five different solvent conditions.The structural diversity indicates that carboxylate ligand adopts the distinct coordination modes and bridging modes to afford different mixed-ligand frameworks and guest-evacuated porosity under different solvent conditions.Significantly,it is found that the specific surface area of PCs is tunned by the porosity of Cd-MOFs,where the later is highly dependent on the solvent.After being fully characterized,we found thatAPC-dmf with the largest specific surface area and total pore volume demonstrates the highest specific capacitance of 156 F g-1 at the current density of 0.5 A g-1.