Rational assembly of functional Co-MOFs via a mixed-ligand strategy: synthesis, structure, topological variation, photodegradation properties and dye adsorption

Abstract

Four novel Co(II) metal–organic frameworks, namely [Co₂(4,4′-cpmb)₂(1,1′-bbi)₂]_n (1), [Co(4,4′-cpmb)(4,4′-bbibp)]_n (2), {[Co(4,4′-cpmb)(tib)]·3(H₂O)}_n (3) and {[Co(4,4′-sdc)(tib)]·(H₂O)}_n (4) (flexible 4,4′-cpmb = 4-(4-carboxylphenylmethylthio)benzoic acid, rigid 4,4′-sdc = 4,4′-stilbenedicarboxylic acid, flexible 1,1′-bbi = 1,1′-(1,4-butanediyl)bis(imidazole), rigid 4,4′-bbibp = 4,4′-bis(benzoimidazo-1-ly)biphenyl and rigid tib = 1,3,5-tris(1-imidazolyl)benzene) were synthesized employing a rational design approach under solvothermal conditions and further characterized by elemental analysis, IR spectra, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. The four Co-MOFs display different interpenetrated structures due to the flexibility of O/N-donor ligands. Single-crystal X-ray diffraction analysis reveals that complex 1 displays a 6-fold interpenetrating class Ia net with the point Schläfli symbol of (6⁶). Complex 2 shows a 3-fold interpenetrating sqc5 net with the point Schläfli symbol of (6⁶·8). Complexes 3 and 4 exhibit a 2-fold interpenetrating 4-connected sql topology with the point Schläfli symbol of (4⁴·6²). The photodegradation properties and dye adsorption capacity of complexes 1–4 are investigated, and the framework integrity of complexes 1–4 can be well-retained.