3D semiconducting Co–MOFs based on 5-(hydroxymethyl)isophthalic acid and imidazole derivatives: syntheses and crystal structures

Abstract

Two three-dimensional cobalt-based metal–organic frameworks with 5-(hydroxymethyl)isophthalic acid (H2HIPA), namely poly[[μ2-1,4-bis(2-methyl-1H-imidazol-1-yl)benzene-κ2 N 3:N 3′][μ2-5-(hydroxymethyl)isophthalato-κ2 O 1:O 3]cobalt(II)], [Co(C9H6O5)(C14H14N4)] n (1), and poly[tris[μ2-1,4-bis(1H-imidazol-1-yl)benzene-κ2 N 3:N 3′]bis[μ3-5-(hydroxymethyl)isophthalato-κ2 O 1:O 3:O 5]dicobalt(II)], [Co2(C9H6O5)2(C12H10N4)3] n (2), were synthesized under similar hydrothermal conditions. Single-crystal X-ray diffraction analyses revealed that 5-(hydroxymethyl)isophthalate (HIPA2−) and 1,4-bis(2-methyl-1H-imidazol-1-yl)benzene (1,4-BMIB) are simple linkers connecting cobalt centres to build a fourfold interpenetration dia framework in complex 1. However, complex 2 is a pillared-layer framework with a (3,6)-connected network constructed by 1,4-bis(1H-imidazol-1-yl)benzene (1,4-DIB) linkers, 3-connected HIPA2− ligands and 6-connected CoII centres. The above significant structural differences can be ascribed to the introduction of the different auxiliary N-donor ligands. Moreover, UV–Vis spectroscopy and Mott–Schottky measurements confirmed that complexes 1 and 2 are typical n-type semiconductors.