Cobalt MOFs base on benzimidazol and varied carboxylate ligands with higher capacitance for supercapacitors and magnetic properties

Abstract

Five new three-dimensional (3D) cobalt-based metal-organic frameworks (MOFs), [Co(L)0.5(1,4-BDC)]n (1), [Co3(L)(1,2,4-TBC)2(H2O)4]n (2), [Co1.5(L)(1,2,4,5-HBTC)(H2O)2]n (3), [Co(L)(5-AIPC)]n (4), and [Co(L)(1,4-NDC)]n (5), (L = 3,6-bis(benzimidazol-1-yl)pyridazine; 1,4-H2BDC = terephthalic acid; 1,2,4-H3BTC = benzene-1,2,4-tricarboxylic acid; 1,2,4,5-H4BTC = benzene-1,2,4,5-tetracarboxylic acid; 5-H2AIPC = aminoisophthalic acid; 1,4-H2NDC = naphthalene-1,4-dicarboxylic acid) have been synthesized, and then characterized by IR spectroscopy, thermogravimetric analysis, elemental analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The structure analysis displays that complexes 1–5 have a 3D network, which 1 displays a 2-fold interpenetrating 3D framework structure with the point symbol of (412·63), 2 have a 8-connected 3D framework structure with the point symbol of (36·414·57·6) and 3 displays a 2,6-connected 3D new topological structure with the point symbol of (44·610·10)(6). Co-MOFs were evaluated as an electrode material for supercapacitors. Complex 1 displayed a higher specific capacitance of 281 F g−1 in 6 M KOH solution at a current density of 1 A g−1 and remained at 195 F g−1 after 2000 cycles at 2 A g−1. In addition, the magnetic properties of complexes 1–5 have been investigated and discussed.