Fe3O4@C@MCM41-guanidine core–shell nanostructures as a powerful and recyclable nanocatalyst with high performance for synthesis of Knoevenagel reaction

Abstract

In this study, preparation, characterization and catalytic application of a novel core–shell structured magnetic with carbon and mesoporous silica shells supported guanidine (Fe3O4@C@MCM41-guanidine) are developed. The Fe3O4@C@MCM41-guanidine was prepared via surfactant directed hydrolysis and condensation of tetraethyl orthosilicate around Fe3O4@C NPs followed by treatment with guanidinium chloride. This nanocomposite was characterized by using Fourier transform infrared spectroscopy, vibrating sample magnetometry, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analysis, wide-angle X-ray diffraction and low-angle X-ray diffraction techniques. This nanocomposite have high thermal, chemical stability, and uniform size. Fe3O4@C@MCM41-guanidine catalyst demonstrated high yield (91–98%) to prepare of Knoevenagel derivatives under the solvent free conditions at room temperature in the shortest time. Also, this catalyst was recovered and reused 10 times without significant decrease in efficiency and stability. Fortunately, an excellent level of yield (98–82%) was observed in the 10 consecutive catalyst cycles.

Highly Efficient One-Pot Conversion of Glucose to 5-Hydroxymethylfurfural over Acid–Base Bifunctional MCM-41 Mesoporous Silica under Mild Aqueous Conditions

“…The FT-IR spectra of MCM-41 and MCM-41/NH-SO 3 H are represented in Figure . For pure MCM-41, the asymmetric and symmetric stretching vibrations of Si–O–Si at 1067 and 806 cm –1 along with the bending mode of Si–O–Si at 462 cm –1 were observed . In the FT-IR spectrum of MCM-41/NH-SO 3 H, beside the characteristic bands of MCM-41, the C–H stretching vibrations of 3-CPTES (2851 and 2954 cm –1 ), the C–C stretching vibrations in the aromatic ring (1415–1445 cm –1 ), the N–H bending vibration of secondary amine (691 cm –1 ), and the S = O stretching vibrations of sulfonic acid groups (1175 cm –1 ) can be further seen. , In parallel, the peak at 958 cm –1 corresponding to the bending mode of Si–OH vanished in the FT-IR spectrum of MCM-41/NH-SO 3 H, demonstrating that 3-CPTES was covalently grafted onto MCM-41 via silylation of surface Si–OH groups .…”

Novel butane sulfonic acid-functionalized core–shell magnetic nanocatalysts for ultrasound-assisted coumarin synthesis

“…[31][32][33][34][35][36][37][38][39][40] Carbon shells were picked out in this work due to their favorable dispersion, high saturation magnetism, and excellent biocompatibility. 27,[41][42][43][44][45][46][47] The shell also makes it possible to modify the surface of nanoparticles with different moieties. 25,27,[31][32][33][34][35][36]41,45,46,48 In light of the aforementioned aspects, novel Fe 3 O 4 @C@PrNH@BuSO 3 H NPs were engineered and manufactured for the first time using a straightforward approach following our prior investigations.…”