Metal-organic frameworks based on rigid ligands as separator membranes in supercapacitor

Two thermally stable MOFs formulated as CoL(1,4-bdc)·2DMF (L = 3,5-bis(5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)pyridine), 1,4-H2bdc = 1,4-benzenedicarboxylic acid) (1) and CdL(4,4'-bpc)·3DMF (4,4'-H2bpc = 4,4'-biphenyldicarboxylic acid) (2) have been solvothermally synthesized and exhibit a similar uninodal 6-connected 3D architecture with {4(12)·6(3)}-pcu topology. MOF1 shows a non-interpenetrated network with larger channel, whereas MOF 2 exhibits a 3-fold interpenetrating framework with smaller pore size. When the two MOFs are used as separator membranes in a supercapacitor, the equivalent series resistance (Res) is larger than the Res in the blank supercapacitor, and the smaller the current density, the more the Res. After being charged and discharged at the low current density, the supercapacitor with MOF 1 as separator membrane (denoted as 1a) possesses a much larger specific capacitance (SC) than the blank supercapacitor, and the amorphous separator membrane 1a shows a more porous morphology than the original MOF membrane 1.