Conjugating proline derivatives onto multi-walled carbon nanotubes: Preparation, characterization and catalytic activity in water

Three proline-based organocatalysts were synthesized by conventional methods and then conjugated onto amino-mOdified multi-walled carbon nanotubes (MWCNTs). The newly prepared MWCNT-based hybrid materials were fully characterized by complementary spectroscopic, thermal and microscopy means and their catalytic activity in the aldol reaction between acetone and 4-nitrobenzaldehyde, in different organic solvents, was evaluated. Although the yield of the reaction was rather low in dimethylsulfoxide, methanol and dichlororomethane, the aldol products were almost quantitatively formed, though with low enantioselectivity, in water. Importantly, the MWCNT-based hybrid materials were recovered by filtration, reused in subsequent catalytic cycles and found retaining their catalytic activity. (C) 2015 Elsevier B.V. All rights reserved.