Catechol‐Functionalized Carbon Nanotubes as Support for Pd Nanoparticles: a Recyclable System for the Heck Reaction

Abstract

AbstractCarbon nanotubes have been covalently functionalized with catechol moieties through the formation of the corresponding aryl radicals obtained by reacting 4‐aminocatechol with isoamyl nitrite. The functionalized multiwalled carbon nanotubes have been in turn used to immobilize Pd(II) ions on its surface forming catechol‐Pd complexes, which were reduced to Pd nanoparticles (NPs). The so‐obtained hybrid material has been characterized by means of thermogravimetric analysis coupled with differential scanning calorimetry (TGA‐DSC), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). This latter technique allowed to estimate the nanoparticle size (5.7±2.8 nm) whereas a palladium loading of 20.3 wt % has been found by inductively coupled plasma optical emission spectroscopy (ICP‐OES). The carbon nanotube‐catechol‐Pd hybrid was used as catalyst in two C−C coupling reactions, namely Suzuki and Heck reactions, resulting recyclable for at least 9 times in the latter process. During the reuse Pd nanoparticles increase their dimension to 19.3±11.7 nm.