Syntheses, Structures, and Properties of Four Metal–Organic Frameworks Based on a N‑Centered Multidentate Pyridine-Carboxylate Bifunctional Ligand

Four new metal–organic frameworks have been synthesized under hydrothermal conditions by the self-assembly of a N-centered multidentate bifunctional ligand (H₂L: 4,4′-((4-(pyridin-4-yl)­phenyl)­azanediyl)­dibenzoic acid) with different N-containing heterocyclic coligands (BIMB = 4,4′-bis­((imidazol-1-yl)­methyl)­biphenyl, BPY = 4,4′-bipyridine, BIP = 1,4-bis­(imidazol-1-yl)­phenyl) and transition metal salts (Co­(NO₃)₂·6H₂O, Zn­(NO₃)₂·6H₂O). They are [Co­(L)­(BIMB)_0.5­(H₂O)]·2DMF (<b>1</b>), [Co­(L)­(BPY)_0.5­(H₂O)₂]­·3DMF­·2H₂O (<b>2</b>), [Zn₂(L)₂]­·4DMF­·3H₂O (<b>3</b>), and [Zn₂(L)₂(BIP)]­·2DMF­·2H₂O (<b>4</b>). Compound <b>1</b> is an infrequent 3,4-connected self-penetration three-dimensional (3D) architecture. Compound <b>2</b> has been classified as a trinodal (3,4,4)-connected 3D <b>sqc69</b> framework. Compound <b>3</b> displays a 2-fold interpenetrating 3D net based on the [Zn₂(CO₂)₄] units which are connected by L^2– ligands. For compound <b>4</b>, the larger potential voids lead to a 4-fold interpenetration, which can be classified as type <b>IIIa</b>. In addition, their thermal stability, the adsorption isotherms, and optical properties have been studied in detail