Environmental challenges prompt researchers to explore innovative and sustainable methods to address crises caused by human activities. One promising approach for ensuring a sustainable future is to investigate safe chemical reactions and processes. In this research, a carbon-based heterogeneous catalyst was constructed from graphene oxide, 2-aminopyrimidine, and methanesulfonic acid. Initially, nanostructured single-layer graphene oxide was prepared using modified Hummers method. The functionalization of graphene oxide was performed using 2-aminopyrimidine, followed by modification with methanesulfonic acid. The structure of the catalyst was confirmed through various analytical procedures, including Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDAX), and X-ray diffraction (XRD). The characterization process provides substantial evidence regarding the structure of the catalyst. The semi-empirical PM6 method, was employed to enhance the understanding of the catalyst and its precursors. The calculations indicate that methanesulfonic acid is adsorbed onto the catalyst's surface via hydrogen bonding, with no proton transfer occurring. To explore the catalytic ability, the production of benzimidazoles from 1,2-phenylenediamine and aldehydes was studied. This study demonstrates that the reported catalyst is highly efficient for the production of benzimidazoles, yielding high outputs without the use of solvents and under sustainable conditions.