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

Abstract

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 {4¹²·6³}-pcu topology. MOF 1 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 (R_es) is larger than the R_es in the blank supercapacitor, and the smaller the current density, the more the R_es. 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.