Cu(ii)/Ni(ii)–organic frameworks constructed from the homometallic clusters by 5-(2-carboxyphenoxy)isophthalic acid and N-ligand: synthesis, structures and visible light-driven photocatalytic properties

Four new complexes, namely, Cu(2)(O-cpia)(btb)(0.5)·(OH) (1), Cu(3)(O-cpia)(2)(bpy)(2) (2), [Ni(2)(O-cpia)(phen)·(OH)·H(2)O]·2H(2)O (3) and [Ni(3)(O-cpia)(2)(bpy)(3)·2H(2)O]·2H(2)O (4) (O-cpia = 5-(2-carboxyphenoxy)isophthalic acid, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, bpy = 4,4′-bipyridine) were successfully isolated under hydrothermal conditions. The four complexes exhibit different architectures constructed from different homometallic clusters varying from mononuclear, binuclear to tetranuclear metal(ii) polyhedra as Second Building Blocks (SBUs). 1 features a 3D framework constructed from the tetranuclear clusters [Cu(4)(μ(3)-OH)(2)] as SBUs, linked with Cu(1)O(4)N and Cu(2)O(5) polyhedra by O-cpia/btb mixed linkers. 2 also exhibits a 3D structure based on trinuclear clusters [Cu(3)(COO)(4)] SBUs, bridged with Cu(1)O(3)N(2) and Cu(2)O(4) polyhedra via O-cpia/bpy mixed ligands. 3 shows a 2D network consisting of tetranuclear clusters [Ni(4)(μ(3)-OH)(2)] SBUs, which are bridged with Ni(1)O(4)N(2) and Ni(2)O(6) through O-cpia ligands. It is worth noting that 4, with a 3D structure, is generated from the binuclear clusters [Ni(2)(COO)(4)] (Ni(1)O(4)N) and mononuclear metal Ni(2) cores (Ni(2)O(4)N(2)) as SBUs, and bridged by O-cpia/bpy mixed ligands. Meanwhile, the degradation of dyes (RhB) by the complexes under visible light irradiation was studied. 1–4 are semiconducting in nature, with E(g) of 1.30 eV (1), 1.78 eV (2), 2.85 eV (3) and 2.14 eV (4). Cu(ii) complexes 1 and 2 are highly efficient photocatalysts for the degradation of RhB under visible light irradiation.