A series of ternary copper(II) complexes were synthesized using a tri‑nitrogen ligand alongside different anionic ligands (Cl , NO3 , AcO , and SO4 2 ). Structural characterization revealed that the geometry of the Cu(II) centers varies significantly with the type of anionic ligand. Positron annihilation techniques demonstrated a direct correlation between the material’s microstructure and the specific anionic ligand bound to copper(II) center. Solid-state analysis showed distinct, highly porous morphologies for each complex, with microstructural prop- erties strongly dependent on the coordinated anionic ligand. These structural differences directly influenced catalytic performance. The complexes exhibited catechol oxidase-like activity in both homogeneous and het- erogeneous systems, with catalytic efficiency correlating with both the microstructural features and the overall structural configuration of the complexes. This study establishes a clear link between anion-modulated structure, solid-state properties, and catalytic function in Cu(II) assemblies.