Construction of Cu(ii), Zn(ii) and Cd(ii) metal–organic frameworks of bis(1,2,4-triazol-4-yl)ethane and benzenetricarboxylate: syntheses, structures and photocatalytic properties

Abstract

Three coordination polymers {[Cu₄(OH)₂(btre)(1,2,3-btc)₂(H₂O)₂]·2H₂O}_n (1), {[Zn₄(OH)₂(btre)(1,2,3-btc)₂(H₂O)₄]·4H₂O}_n (2) and {[Cd₃(btre)(1,2,3-btc)₂(H₂O)₃]·3H₂O}_n (3) were synthesized by the hydrothermal method using 1,2-bis(1,2,4-triazol-4-yl)ethane (btre), 1,2,3-benzenetricarboxylate (1,2,3-btc) and metal ions (Cu(II), Zn(II), and Cd(II)). 1 shows a (3,8)-connected 3D metal–organic framework based on the tetranuclear copper(II) cluster [Cu₄(μ₃-OH)₂] with the point symbol of (4·5²)₃(4⁴·5⁵·6¹²·7³·8³·9). 2 exhibits a (3,8)-connected 3D metal–organic framework based on the tetranuclear zinc(II) cluster [Zn₄(μ₃-OH)₂] with the point symbol of (4²·6)₃(4⁶·6¹⁸·8³·10). In 3, each [Cd₃(1,2,3-btc)₂(H₂O)]_n chain connects four adjacent identical [Cd₃(1,2,3-btc)₂(H₂O)]_n chains through the btre bridges in four different directions, leading to an unusual 3D network. 3 shows a 4-connected 6⁶dia topological net based on the [Cd₃(H₂O)(COO)₄] trimer Cd(II) clusters. The diverse structures demonstrate that the central metal ions play the key role in the assembly of coordination polymers. 1 and 2 show good photocatalytic activity for the degradation of methyl orange. The luminescence of 2 and 3 was investigated.