<p>In this study, we examined the potential ability of the sulfonated melamine–formaldehyde resin (SMFR) as an acidic heterogeneous catalyst in the multicomponent synthesis of 3, 4-dihydropyrimidine. The incorporation of sulfonic acid groups into the melamine–formaldehyde resin framework resulted in a highly active and recyclable catalyst, promoting reactions under mild and environmentally friendly conditions. Key advantages of this method include short reaction times, high product yields, and efficient catalysis with minimal catalyst loading. The synthesized compounds were structurally confirmed through FT-IR, ¹³C NMR, and ¹H NMR spectroscopy, demonstrating the efficiency and reliability of the catalytic system under green synthesis conditions.</p> Graphical Abstract <p></p>