A novel 3D coordination polymer {[Cu_4.5 (BTZE)_1.5 (μ₃-OH)₃(μ-OH)(SO₄)(H₂O)_1.5·4H₂O]}_n (1) was synthesized by a solvothermal reaction of 1,2-bis(tetrazol-5-yl) ethane (BTZE) with copper sulfate. Compound (1) contained triangular [Cu₃(μ₃-OH)] cluster based magnetic Δ-chains linked with in situ generated μ₂-BTZE ligands to form a 2D cyclic annular layer. This 2D layer structure was further modified with sulfate and symmetry-related μ₃-OH groups, extending to a 3D coordination framework structure. The magnetic performance of (1) was characterized in the temperature range of 2–300 K in terms of direct-current and alternating-current magnetic susceptibilities, revealing that (1) was a canted ferromagnet with a critical temperature (T_c) of 9.5 K. Notably, (1) behaved as a hard magnet with a coercive field of 2.3 kOe at 2 K, showing significant unique characteristics compared to those of the reported spin canting systems based on pure Cu(II) ions.