Development of heterogeneous
catalysts from biomass-derived activated
carbon is a challenging task. Biomass-derived activated carbon possesses
a large specific surface area, highly porous structure, and good thermal/chemical
stability. Magnetic copper catalysts based on biomass-derived activated
carbon exhibited good catalytic activity in base-free Chan–Lam
coupling and oxidations. Herein, biomass-derived activated carbon
was prepared by the carbonization of neem dead leaves (abundant waste
biomass) followed by chemical activation with KOH. Such a porous carbon
material was used as a low cost and highly efficient support material
for the preparation of inexpensive and environmentally benign magnetic
catalysts [Cu@KF-C/MFe2O4, M = Co, Cu, Ni, and
Zn]. In addition, KF modification was done to impart basic character
to the catalyst that can perform C–N coupling under base-free
conditions. Initially, Brunauer–Emmett–Teller (BET)
analysis of the synthesized catalysts was carried out, which indicated
that Cu@KF-C/CoFe2O4 possess more surface area
as well as pore volume, and so accounting for the highest activity
among the other synthesized catalysts. Further, X-ray photoelectron
spectroscopy (XPS) analysis was performed, which inferred that Cu@KF-C/CoFe2O4 contains most of the copper in reduced form,
i.e., Cu(0), which is the active species responsible for better catalytic
activity toward Chan–Lam coupling reactions as well as oxidation
of alcohols and hydrocarbons. The physiochemical properties of the
most active catalyst, Cu@KF-C/CoFe2O4, was examined
by BET, XPS, Fourier transform infrared Spectroscopy (FTIR), thermogravimetric
analysis (TGA), field emission gun scanning electron microscopy (FEG-SEM),
high-resolution transmission electron microscopy (HR-TEM), energy
dispersive X-ray (EDX) mapping, energy dispersive X-ray (EDX), inductively
coupled plasma atomic emission spectroscopy (ICP-AES), powder X-ray
diffraction (XRD), and vibrating sample magnetometry (VSM). Moreover,
Cu@KF-C/CoFe2O4 shows excellent stability as
well as reusability and could be easily separated with the help of
an external magnet.
