Design and synthesis of graphene-supported molybdenum complexes as efficient catalysts for the Hantzsch reaction

Two innovative molybdenum-based catalysts, designated as Mo-1-f-AP-f-GO (3) and Mo-2-f-AP-f-GO (4), were synthesized by anchoring molybdenum complexes onto aminopropyltriethoxysilane (APTES)-functionalized graphene oxide (GO). These catalysts were prepared through the reaction of aminated graphene oxide (NH₂-f-GO) with molybdenum complexes [(MoO₂)₂(L^Cl-sacyl)₂(H₂O)₂] (1) and [(MoO₂)₂(L^Cl-hap)₂(H₂O)₂] (2) in equimolar ratios. Comprehensive characterization of the synthesized materials was performed utilizing a suite of analytical methods. These analyses confirmed the successful functionalization of GO and the effective immobilization of the molybdenum complexes. The catalytic performance of these materials was evaluated in a single closed vessel, three-component Hantzsch reaction, involving ethyl acetoacetate (EAA), benzaldehyde, and ammonium acetate (NH₄OAc) in the presence of oxidant. The reaction proceeded efficiently, yielding pyridine derivatives with high conversion rates. After the reaction, the catalysts were easily recovered through washing and drying, and demonstrated consistent activity over multiple catalytic cycles, highlighting their potential for sustainable and recyclable catalytic applications.