In the present study, the synthesis of 3 and 4-dihydropyrimidinone and thiones was investigated by Biginelli reaction in the presence of carbon dioxide nanoparticles (MWCNT COOH) as a catalyst. The use of carbon nanotubes has many advantages, including ease of product separation, catalyst recovery capability, and environmental compatibility compared to liquid acidic catalysts. These catalysts are insoluble in most organic solvents and cause little corrosion. In addition, the catalyst is recovered without any reduction in its activity. Therefore, these catalysts can be used as a substitute for catalysts such as sulfuric acid. To investigate the effect of the catalyst on the organic reaction mentioned and to find the optimal conditions, first the synthesis of a derivative is selected as the reaction model and the effect of different reaction conditions such as the amount of catalyst, solvent type and temperature on it is examined. Other derivatives were then prepared under optimal conditions. In most cases, high product efficiency was achieved in a relatively short period of time. Comparing the conditions and results of the reactions performed in this study with other methods reported in the articles shows that the catalyst studied in this study was able to make the conditions of the reaction discussed in terms of time and efficiency, simple separation of products possible.