Cu(I) nanoparticles (NPs) on modified poly(styrene-co-maleic anhydride) was prepared via a facile procedure. In this regard the modified co-polymer (SMA) was initially synthesized from the reaction of poly(styrene-co-maleic anhydride) with 3-aminopyridine. Upon the treatment of CuI with SMA, Cu(I) NPs were immobilized on SMA. This immobilized Cu(I) NPs was fully characterized by FTIR, SEM and EDAX analysis methods. Moreover, the interaction of Cu cations with 3-aminopyridine modified SMI catalyst via density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) computationally was studied. Our calculated results demonstrated that among 2,3 and 4 substituted aminopyridines for the modification of SMA, the 3-amnopyridine has the weakest ligand and Cu(I) interaction. However, the SMI image showed a suitable size of nanoparticles and inductively coupled plasma (ICP) analysis showed a higher Cu content in comparison with those of 2 and 4-substituted pyridines. The catalytic activity and reusability of this nanocatalyst system of 3-substituded aminopyridines was examined in the Huisgen 1,3-dipolar cycloaddition via click reaction. The reactions proceeded smoothly leading to regioselective synthesis of 1,4-disubstitued 1,2,4-triazole derivatives in excellent yields under mild reaction conditions. This heterogeneous catalytic system was separated easily by simple filtration and was reused without pre-activation at least in five runs without appreciable loss in its activity.