Variation of topologies and entanglements in metal–organic frameworks with mixed tris[4-(1H-imidazol-1-yl)phenyl]phosphine oxide and dicarboxylate ligands

Abstract

Six metal–organic frameworks with the combination of a novel tripodal ligand tris[4-(1H-imidazol-1-yl)phenyl]phosphine oxide (tipo) and different polycarboxylates, namely [Zn₂(bpdc)₂(tipo)(H₂O)]·5H₂O (1), [Cd(tipo)₂][Cd₂(bdc)₃]·4H₂O (2), [Cd₂(ndc)₂(tipo)₂]·3H₂O (3), [Cd₂(bpedc)₂(tipo)₂]·15H₂O (4), [Cd₂(hfdc)₂(tipo)₂]·10H₂O (5) and [Ni₂(tipo)₂(bpedc)(H₂O)₄]·2NO₃·2DMF (6), were synthesized and structurally characterized. Compound 1 featured a 2D → 3D parallel polycatenation of a 3,3,4-connected net with an unusual 4 degrees of catenation and an index of separation of 2. Compound 2 showed an unprecedented polycatenation of charged networks 2D kgd and 3D pcu constructed by different organic ligands. Compound 3 exhibited a combination of a 2D → 3D parallel polycatenation of the sql net and polythreading. Compound 4 featured a 4-fold interpenetration of a 3,5-connected 3,5T1 net. Compound 5 displayed an unusual 2-fold interpenetration of the sdd net. Compound 6 presented a 2-fold interpenetration of the 3,4-connected bey net with a cationic framework. The luminescence properties of 1–5 in the solid state were investigated. Also, compound 6 showed a tendency for rapid selective dye capture and highly efficient Cr₂O₇²⁻ removal from aqueous solution.