Zn-MOFs-Derived Carbon Materials Applied In Electric Double-layer Capacitors

Metal-organic frameworks?MOFs?is a novel porous of materials with larger specific surface,tunable pore size and highly ordered architecture,which has attracted the attention of many researchers in recent years.Due to their structure and function can be tailored for on demand applications,MOFs can be used as precursors for the preparation of multi-functional carbon materials.MOF-derived carbon materials exhibit excellent specific surface area,hierarchical pore structure,high porosity and good electrical conductivity,and these outstanding properties make them attractive to be used in various applications such as purification of environment,energy storage systems and catalysts.In this paper,six zinc metal-organic frameworks?Zn-MOFs?,have been obtained from the reactions of 4,4?-bis?imidazol-1-yl?-biphenyl?bibp?with a series of zinc metal salts under solvent-diffusion method.And we utilized these Zn-MOFs as precursors to further prepare porous carbon materials and carbon aerogels?PCs and CAs?through the calcination-thermolysis procedure.These MOFs derived carbon as electrode materials in the supercapacitor display excellent electrochemical properties of electric double-layer capacitors?EDLCs?.The research contents have been summarized as following:1.Five Zn-MOFs 1-5 crystals with different anions have been synthesized via solvent-diffusion method,which based on 4,4?-bis?imidazol-1-yl?-biphenyl as the organic ligand and five zinc metal salts[ZnCl₂,Zn?BF₄?₂,Zn?CF₃SO₃?₂,ZnSO₄,and ZnBr₂].Due to the in situ activation affect of ZnCl₂ in MOF 1,PC-1 poesseses the highest specific surface area(1999.4 m² g^-1).B,N-codoped carbon material?PC-2?was obtained by the influence of anionic BF₄^-in Zn-MOF 2.For Zn-MOF 3-4,ZnS particles were obtained because of in-situ sulfurization effect after calcination,which affected the pore-forming effect of zinc on the derived carbon materials.Overall,it is found that anion not only affect the topological structure of MOF,but also play an important role in the specific surface area and surface functional properties of its derived porous carbon materials?PCs 1-5?,which makes it have great difference in electrochemical properties of supercapacitors.Importantly,PC-1 also exhibits the highest specific capacitance of 199 F g^-1 at 0.5 A g^-1 in the electric double-layer capacitors.2.We integrate the puffing effects of perchlorate ion and zinc species,and ingeniously synthesized Zn-MOF 6 with the ClO₄^-ion.By simulating the charcoaling procedure,we press Zn-MOF 6 powder into pellets and then carry out the calcination-thermolysis process to obtain one monolithic CAs?CA-1?MOF?.CA-1?MOF displays large specific surface area,low density(5.6 mg·cm^-3),high inherent porosity,optimized pore distribution?concomitance of micro/meso/macropores?and good conductivity.CA-1?MOF exhibits the higher specific capacitance of 313 F g^-1 at 5 mV s^-1,and the corresponding symmetric supercapacitor cell?SSC?achieves remarkable energy density of 20.7 Wh Kg^-1 at power density of 350 W Kg^-1.Furthermore,CA-1?MOF shows excellent cycling stability and reversibility,and the loss of capacitance is only 4.8%even after 10000 cycles at 1 A g^-1.