Assembly of a series of d10 coordination polymers based on W-shaped 1,3-di(2′,4′-dicarboxyphenyl)benzene: from syntheses, structural diversity, luminescence, to photocatalytic properties

Abstract

Solvothermal reactions of W-shaped 1,3-di(2′,4′-dicarboxyphenyl)benzene (H₄DDB) and zinc(II) or cadmium(II) salts in the presence or absence of three ancillary bridging imidazole linkers afford six CPs, namely, [Zn(H₂DDB)(H₂O)₂(μ₂-H₂O)]_n (1), [Zn₂(DDB)(1,4-bimb)]_n (2), [Zn₂(DDB)(1,3-bimb)]_n (3), {[Zn₄(DDB)(HDDB)(1,3-bmib)₂Cl]·H₂O}_n (4), {[Cd₂(DDB)(1,3-bimb)]·H₂O}_n (5), and {[Cd₂(DDB)(1,3-bmib)(H₂O)_0.5]·H₂O}_n (6), (1,3-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, 1,4-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene, and 1,3-bmib = 1,3-bis(2-methylimidazol-1-ylmethyl)benzene). Complex 1 is composed of [Zn(H₂DDB)(H₂O)₂(μ₂-H₂O)]_n chains, which are further extended to a 3D supramolecular structure via hydrogen bonds. Complexes 2 and 3 exhibit the same (3,4,6)-connected net with the Schläfli symbol (5²·6²·8·9)(5²·6)₂(5⁴·6⁴·7²·8³·9·10) built from two kinds of SBUs: [Zn₂(COO)₄] and [Zn₂(COO)₂], while complex 4 is another (3,4,6)-connected net with the Schläfli symbol (3·4·5·6²·7)(3·4·5·6⁷·7³·8²)(3·7²), based on the same [Zn₂(COO)₂] and [Zn₂(COO)₄] SBUs. The two Cd^II complexes of 5 and 6 display 3D (3,10)-connected (4¹⁰·6³²·8³)(4³)₂ nets, consisting of {Cd₄(COO)₈} and [Cd₄(COO)₈(μ₂-H₂O)] SBUs, respectively. The thermal stability and luminescence properties of complexes 1–6 have been investigated. In addition, complexes 1–6 show excellent photocatalytic activity for methylene orange (MO) dye degradation in aqueous solution under UV light. And complexes 2–6 exhibit relatively good chemical stability in aqueous solutions with pH regulated from 2 to 12.