Nickel supported on magnetic biochar as a highly efficient and recyclable heterogeneous catalyst for the one‐pot synthesis of spirooxindole‐dihydropyridines

A multidentate copper complex on magnetic biochar nanoparticles as a practical and recoverable nanocatalyst for the selective synthesis of tetrazole derivatives

Waste recycling, novel and easy methods of recycling catalysts, use of green solvents, use of selective catalysts and preventing the production of by-products are the most important principles of green chemistry and modern technology. Therefore, in this work, biochar nanoparticles (B-NPs) were synthesized by the pyrolysis of chicken manure as a novel method for waste recycling. Subsequently, the B-NPs were magnetized by Fe(0) nanoparticles to improve the easy recovery of biochar. Then, the surface of biochar magnetic nanoparticles (FeB-MNPs) was modified by (3-chloropropyl)trimethoxysilane (3Cl-PTMS). Finally, a multidentate copper complex of 2,2'-(propane-1,3-diylbis(oxy))dianiline (P.bis(OA)) was immobilized on the surface of modified FeB-MNPs, which was labeled as Cu-P.bis(OA)@FeB-MNPs. Cu-P.bis(OA)@FeB-MNPs was investigated as a commercial, homoselective, practical, and recyclable nanocatalyst in the synthesis of 5-substituted-1H-tetrazole compounds through the [3 + 2] cycloaddition of sodium azide (NaN3) and organo-nitriles in polyethylene glycol 400 (PEG-400) as a green solvent. Cu-P.bis(OA)@FeB-MNPs was characterized using wavelength dispersive X-ray (WDX) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), vibrating-sample magnetometer (VSM), atomic absorption spectroscopy (AAS) and N2 adsorption-desorption (Brunauer-Emmett-Teller (BET) method) techniques. Cu-P.bis(OA)@FeB-MNPs was recovered and reused for several runs in the synthesis of tetrazoles.

Greener design and characterization of biochar/Fe3O4@SiO2-Ag magnetic nanocomposite as efficient catalyst for synthesis of bioactive benzylpyrazolyl coumarin derivatives

The study aimed to develop an efficient catalyst, biochar/Fe₃O₄@SiO₂-Ag magnetic nanocomposite, to synthesize bioactive benzylpyrazolyl coumarin derivatives through a one-pot multicomponent reaction. The catalyst was prepared using Ag nanoparticles synthesized with Lawsonia inermis leaf extract and carbon-based biochar obtained through pyrolysis of Eucalyptus globulus bark. The nanocomposite contained a silica-based interlayer, highly dispersed Ag nanoparticles, and a central magnetite core, which responded well to external fields. The biochar/Fe₃O₄@SiO₂-Ag nanocomposite showed excellent catalytic activity and could be easily recovered using an external magnet and reused five times without significant loss of performance. The resulting products were tested for antimicrobial activity and showed significant activity against various microorganisms.

Design and characterization of an urea-bridged PMO supporting Cu(II) nanoparticles as highly efficient heterogeneous catalyst for synthesis of tetrazole derivatives

In this work, a new periodic mesoporous organosilica with urea-bridges produced by the reaction of (3-aminopropyl)triethoxysilane and toluene-2,4-diisocyanate (APS-TDU-PMO) is introduced. The obtained APS-TDU-PMO was found to be an appropriate support for loading of Cu(II) nanoparticles to afford supramolecular Cu@APS-TDU-PMO nanocomposite. Uniformity and mesoporosity of both synthesized nanomaterials including APS-TDU-PMO and Cu@APS-TDU-PMO were proved by different spectroscopic, microscopic or analytical techniques including FTIR, EDX, XRD, FESEM, TEM, BET, TGA and DTA. Furthermore, the prepared Cu@APS-TDU-PMO nanomaterial was also used, as a heterogeneous and recyclable catalyst, for the synthesis of tetrazole derivatives through cascade condensation, concerted cycloaddition and tautomerization reactions. Indeed, the main advantages of this Cu@APS-TDU-PMO is its simple preparation and high catalytic activity as well as proper surface area which enable it to work under solvent-free conditions. Also, the introduced Cu@APS-TDU-PMO heterogeneous catalyst showed good stability and reusability for six consecutive runs to address more green chemistry principles.