Hierarchical Micro/Mesoporous MCM-41@ZIF-8/Ni catalyst for accelerating the synthesis of spiro derivatives of pyrimido[4,5-b]quinolines and pyrazolo[3,4-b]quinolones

In this study, a new hierarchical micro/mesoporous catalyst is prepared via the synthesis of a metal-organic framework (ZIF-8/Ni) on mesoporous silica (MCM-41) and characterized by various analytical techniques including FT-IR, XRD, ICP, FESEM, EDX, TEM, TGA, and BET. The combination of MCM-41 and ZIF-8/Ni in a single catalytic system can provide a synergistic effect between the two porous structures, resulting in superior catalytic activity. The prepared catalyst was successfully applied to the synthesis of a series of spiro pyrimido[4,5- b ]quinoline and pyrazolo[3,4- b ]quinolone derivatives, several of which have not been previously reported. The studied reactions were performed using a water–ethanol solvent system under mild conditions, affording the desired products with high isolated yields without the need for column chromatography or tedious purification steps. Moreover, the catalyst exhibited excellent reusability and maintained high activity over several consecutive runs, highlighting its potential as a sustainable and reusable heterogeneous catalyst for environmentally friendly organic synthesis.