The diverse structures of Cd(ii) coordination polymers with 1,3,5-benzenetribenzoate tuned by organic bases

Abstract

The reaction of CdCl2·1.5H2O with 1,3,5-benzenetribenzoic acid (H3BTB) in DMF gave {[Cd3(BTB)2(DMF)4]·3DMF}n (1), while the reactions of Cd(Ac)2·2H2O with H3BTB in DMF/H2O (1 : 10) in the presence of py, bpy, and bib generated {(Hpy)[Cd(BTB)(py)]·0.5DMF·3H2O}n (2), {Cd[Cd2(BTB)2(bpy)]·2bpy·DMF·19H2O}n (3), and {[Cd3(BTB)2(bib)3(H2O)2]·4H2O}n (4), respectively (DMF = N,N′-dimethylformamide, py = pyridine, bpy = 4,4′-bipyridine, bib = 1,4-bis(imidazol-1-yl)butane). X-Ray single-crystal analyses reveal that 1 contains a two-dimensional bilayer structure based on a carboxylate and DMF bridged Cd3 cluster. In 2, two honeycomb-like [Cd(BTB)]nn− sheets are interpenetrated with each other to form a 2D network. In 3, the 2D [Cd(BTB)]nn− honeycomb-like sheets are pillared by bpy to form a 3D framework, and the 3D frameworks are three-fold interpenetrated to generate the framework of 3 with 1D open channels, which are occupied by disordered Cd ions, bpy, DMF and water molecules. Compound 4 consists of a 3D self-penetrated framework constructed by μ2-bib bridging five-fold interpenetrated 2D bilayers. The results of gas sorption measurements indicate that the desolvated 3 can selectively adsorb CO2 and H2 over N2, with a rare large hydrogen sorption hysteresis. The luminescent properties of 1–4 were also investigated.