Ecological recycling
of waste materials by converting them into
valuable nanomaterials can be considered a great opportunity for management
and fortification of the environment. This article deals with the
environment-friendly synthesis of Fe2O3 nanoparticles
(composed of α-Fe2O3 and γ-Fe2O3) using waste toner powder (WTP) via calcination. Fe2O3 nanoparticles were then
coated with silica using TEOS, functionalized with silane (APTMS),
and immobilized with Co(II) to get the desired biocompatible and cost-effective
catalyst, i.e., Co(II)-NH2-SiO2@Fe2O3. The structural features in terms of
evaluation of morphology, particle size, presence of functional groups,
polycrystallinity, and metal content over the surface were determined
by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction
(P-XRD), field emission gun-scanning electron microscopy (FEG-SEM),
energy-dispersive X-ray analysis (EDX), high resolution-transmission
electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS),
thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM),
Brunauer–Emmett–Teller (BET) analysis, and inductively
coupled plasma-atomic emission spectroscopy (ICP-AES) studies. XPS
confirmed the (II) oxidation state of Co, and ICP-AES and EDX supported
the loading of Co(II) over the surface of the support. P-XRD proved
the polycrystalline nature of the Fe2O3 core
and even after functionalization. In comparison to previously reported
methods, Co(II)-NH2-SiO2@Fe2O3 provides an eco-friendly procedure for the synthesis of polyhydroquinoline
and quinazoline derivatives with several advantages such as a short
reaction time and high yield. Polyhydroquinoline and quinazoline derivatives
are important scaffolds in pharmacologically active compounds. Moreover,
the developed nanocatalyst was recyclable, and HR-TEM and P-XRD confirmed
the agglomeration in the recycled catalyst resulted in a decrease
in yield after the fifth run. The present protocol provides a new
strategy of recycling e-waste into a heterogeneous nanocatalyst for
the synthesis of heterocycles via multicomponent
reactions. This made the synthesized catalyst convincingly more superior
to other previously reported catalysts for organic transformations.
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