Molybdenum trioxide-decorated carbon nanotubes: An efficient and reusable catalyst for cross-dehydrogenative coupling-type aza-Henry reaction in aqueous media

Abstract

Highly efficient and reusable heterogeneous molybdenum trioxide (MoO3) catalysts were prepared by anchoring MoO3 nanoparticles onto thiolated carbon nanotubes (CNTs). Transmission electron microscopy and X-ray diffraction analyses showed that the orthorhombic-structured MoO3 nanoparticles were successfully anchored onto the surface of the CNTs, and the average particle size was approximately 2.6 nm. We evaluated the applicability of the prepared catalyst in the cross-dehydrogenative coupling-type aza-Henry reaction of N-phenyl-1,2,3,4-tetrahydroisoquinoline with nitromethane. The catalyst showed very good reactivity in water; the used catalyst could be readily recovered by simple filtration and reused eight times with almost unchanged activity. The high reactivity and good reusability can be attributed to the high surface area of the nanosized catalysts and the strong adhesion between MoO3 and thiolated CNTs.