Novel coordination polymers of Zn(ii) and Cd(ii) tuned by different aromatic polycarboxylates: synthesis, structures and photocatalytic properties

Abstract

Tuned by different aromatic polycarboxylates, six fascinating coordination polymers (CPs), namely, [Cd(pbmb)(p-bdc)]_n (1), {[Zn₃(pbmb)₂(1,3,5-btc)₂]·6H₂O}_n (2), {[Cd₃(pbmb)₃(1,3,5-btc)₂(H₂O)]·3H₂O}_n (3), {[Zn₂(pbmb)(1,2,3-btc)(μ₂-OH)]·H₂O}_n (4), [Cd(pbmb)(1,2,4,5-btec)_0.5]_n (5), and {[Cd(pbmb)(sdba)]·2H₂O}_n (6) (pbmb = 1,1′-(1,3-propane)bis-(2-methylbenzimidazole), p-H₂bdc = 1,4-benzenedicarboxylic acid, 1,3,5-H₃btc = 1,3,5-benzenetricarboxylic acid, 1,2,3-H₃btc = 1,2,3 benzenetricarboxylic acid, 1,2,4,5-H₄btec = 1,2,4,5-benzenetetracarboxylic acid, H₂sdba = 4,4′-sulfonyldibenzoic acid), have been ideated and synthesized by hydrothermal reaction methods. Structural analyses reveal that complexes 1–3 feature three-dimensional (3D) structures (1: 4-connected 6⁶ topology, 2: (3,4,6)-connected (6⁵·7)(4·6²)₂(4²·6⁶·8⁵·10²) topology and 3: (2,3,4)-connected (6⁵·8)₂(6³)₂ topology), and the remaining CPs 4–6 exhibit 2D networks. The thermal stability and powder X-ray diffraction for 1–6 have been investigated as further properties. The optical band gaps are analyzed by diffuse-reflectance UV-vis spectra. Moreover, all of the materials manifest good photocatalytic activities for the degradation of methylene blue (MB) (1: 74%, 2: 41%, 3: 37%, 4: 76%, 5: 46%, 6: 75%, respectively) in water under the irradiation of a high-pressure mercury lamp.