Sulfonated multiwalled carbon nanotubes (MWCNTs) as a new, efficient, and recyclable heterogeneous nanocatalyst for the synthesis of amines

Abstract

Sulfonated multiwalled carbon nanotubes (MWCNTs) were synthesized by chemical vapor deposition (CVD) as a new and facile one-pot method using acetylene (as the CNT precursor), thiophene (as the sulfur precursor), and ferrocene (for in situ liberation of metal nanoparticles as the CNT nanocatalyst). A low catalytic amount of the resulting sulfonated MWCNTs with a turnover number (TON) up to 980 and a turnover frequency (TOF) up to 11 160 h–1 was utilized as a new and recyclable heterogeneous nanocatalyst for the efficient one-pot synthesis of various amines (secondary and tertiary) by direct reductive amination of aldehydes and ketones using NaBH4. The catalyst was easily isolated from the reaction mixture by simple filtration and reused at least five times without significant degradation in activity.