The influence of solvent controlled morphology on capacitive properties of metal-organic frameworks based on polyaminocarboxybenzene ligands

Abstract

In order to overcome the low capacitive performance of traditional metal organic frameworks (MOFs) applied to supercapacitors, a novel conjugated small molecule monomer(3,5-diaminobenzoic acid, DABA) with amino and carboxyl groups was used as a ligand, and Ni and Co ions as metal nodes to construct novel highly electroactive bimetallic MOF(DABA-MOF) materials through a simple one-step solvothermal method. The structure and capacitive performance of obtained DABA-MOF in three organic solvents with different polarities and degrees of deprotonation (methanol, ethanol, N,N-dimethylformamide) was investigated, and it was found that with the increase of solvent deprotonation degree, the morphology of DABA-MOF with the coexistence of amino and carboxyl groups gradually changes from a smooth rod-shaped solid structure to a rough hydrangea-like structure, and the corresponding capacitive performance of DABA-MOF is also gradually enhanced. In particular, DABA-MOF synthesized in DMF can reach a maximum specific capacitance of 621 C g−1 at 1 A g−1, and the capacitance remains as high as 81.05% even after 5000 cycles, which exhibit excellent capacitance properties. This study shows that it has potential advantages to select the mixed coordination active MOF with amino and carboxyl groups as the electrode material for supercapacitor, and the deprotonation degree of solvent has a great influence on the structure and morphology of MOF with mixed active coordination sites.