Four new complexes, namely, Cu₂(O-cpia)(btb)_0.5·(OH) (1), Cu₃(O-cpia)₂(bpy)₂ (2), [Ni₂(O-cpia)(phen)·(OH)·H₂O]·2H₂O (3) and [Ni₃(O-cpia)₂(bpy)₃·2H₂O]·2H₂O (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 [Cu₄(μ₃-OH)₂] as SBUs, linked with Cu(1)O₄N and Cu(2)O₅ polyhedra by O-cpia/btb mixed linkers. 2 also exhibits a 3D structure based on trinuclear clusters [Cu₃(COO)₄] SBUs, bridged with Cu(1)O₃N₂ and Cu(2)O₄ polyhedra via O-cpia/bpy mixed ligands. 3 shows a 2D network consisting of tetranuclear clusters [Ni₄(μ₃-OH)₂] SBUs, which are bridged with Ni(1)O₄N₂ and Ni(2)O₆ through O-cpia ligands. It is worth noting that 4, with a 3D structure, is generated from the binuclear clusters [Ni₂(COO)₄] (Ni(1)O₄N) and mononuclear metal Ni(2) cores (Ni(2)O₄N₂) 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.