In this article, the mesoporous silica framework of KIT‐6 was synthesized and, then its surface was modified using 3‐aminopropyltrimethoxysilane (APTMS). The new KIT‐6@DABP@Cu nanocatalyst was then prepared by anchoring the copper complex on modified mesoporous KIT‐6. The nanocatalyst was identified using several techniques, including FT‐IR, WDX, AAS, SEM, TGA, XRD, EDS, and BET. The physical properties, such as size, shape, and morphology of the nanocatalyst were studied by SEM analysis. The elemental composition of KIT‐6@DABP@Cu nanocatalyst was described using wavelength dispersive X‐ray spectroscopy (WDX) and EDS. FT‐IR spectroscopy was used to characterize the functional groups in the structure of the nanoparticles. The stability of KIT‐6@DABP@Cu nanocatalyst was studied by TGA at high temperatures. Also, the surface area, total volume, and average diameter of pores of the nanocatalyst were determined using Brunauer–Emmett–Teller (BET) analysis. The KIT‐6@DABP@Cu catalyst was found to be a new, highly effective, and green catalyst for the synthesizing of 5‐substituted‐tetrazoles using nitriles and sodium azide (NaN3) catalyzed in polyethyleneglycol‐400 (PEG‐400) as a green solvent. This heterogeneous catalyst showed good recyclability for up to five consecutive cycles without notable loss of its catalytic efficiency.