Recent Advances on Heteroatom-Doped Porous Carbon/Metal Materials: Fascinating Heterogeneous Catalysts for Organic Transformations.

Design and preparation of low-cost, effective, and novel catalysts are important topics in the field of heterogeneous catalysis from academic and industrial perspectives. Recently, heteroatom-doped porous carbon/metal materials have received significant attention as promising catalysts in divergent organic reactions. Incorporation of heteroatom into the carbon framework can tailor the properties of carbon, providing suitable interaction between support and metal, resulting in superior catalytic performance compared with those of traditional pure carbon/metal catalytic systems. In this review, we try to underscore the recent advances in the design, preparation, and application of heteroatom-doped porous carbon/metal catalysts towards various organic transformations.

Diphenyl diselenide grafted onto a Fe3O4-chitosan composite as a new nanosorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction.

Diphenyl diselenide was immobilized on chitosan loaded with magnetite (Fe3O4) nanoparticles to give an efficient and cost-effective nanosorbent for the preconcentration of Pb(II), Cd(II), Ni(II) and Cu(II) ions by using effervescent salt-assisted dispersive magnetic micro solid-phase extraction (EA-DM-µSPE). The metal ions were desorbed from the sorbent with 3M nitric acid and then quantified via microflame AAS. The main parameters affecting the extraction were optimized using a one-at-a-time method. Under optimum condition, the limits of detection, linear dynamic ranges, and relative standard deviations (for n = 3) are as following: Pb(II): 2.0 ng·mL-1; 6.3-900 ng·mL-1; 1.5%. Cd(II): 0.15 ng·mL-1; 0.7-85 ng·mL-1, 3.2%; Ni(II): 1.6 ng·mL-1,.6.0-600. ng·mL-1, 4.1%; Cu(II): 1.2 ng·mL-1, 3.0-300 ng·mL-1, 2.2%. The nanosorbent can be reused at least 4 times. Graphical abstract Fe3O4-chitosan composite was modified with diphenyl diselenide as a sorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction.

N/Se co-doped porous carbon catalyst derived from a deep eutectic solvent and chitosan as green precursors: Investigation of catalytic activity for metal-free oxidation of alcohols.

Heteroatom-doped porous carbon-based materials with high surface area compared to their metal-based homologs are considered environmentally friendly and ideal catalysts for organic reactions. In this paper, a new method for the convenient fabrication, cost-effective, and high efficiency of nitrogen/selenium co-doped porous carbon-based catalysis (marked as N/SePC-T) was designed. The N/SePC-T catalysts were created from the direct pyrolysis of a eutectic solvent containing choline chloride/urea as the nitrogen-rich carbon source, selenium dioxide as a source of heteroatom and chitosan as a secondary carbon source in different temperatures (T). The efficacy of the carbonization temperature on the pore structure, morphology, and catalytic activity of the N/SePC-T materials was investigated and displayed, the N/SePC-900 (having a surface area of 562.01 m2/g and total pore volume of 0.2351 cm3 g-1) has the best performance. The morphology, structure, and physicochemical properties of N/SePC-900 were characterized using various analyses including XRD, TEM, TGA, FE-SEM, EDX, FT-IR, XPS, and Raman. The optimized N/SePC-900 catalyst indicated excellent catalytic performance in the oxidation of benzylalcohols to corresponding aldehydes in very mild conditions.

Copper oxides supported sulfur-doped porous carbon material as a remarkable catalyst for reduction of aromatic nitro compounds.

Synthesis and manufacturing of metal-organic framework derived carbon/metal oxide nanomaterials with an advisable porous structure and composition are essential as catalysts in various organic transformation processes for the preparation of environmentally friendly catalysts. In this work, we report a scalable synthesis of sulfur-doped porous carbon-containing copper oxide nanoparticles (marked CuxO@CS-400) via direct pyrolysis of a mixture of metal-organic framework precursor called HKUST-1 and diphenyl disulfide for aromatic nitro compounds reduction. X-ray diffraction, surface area analysis (BET), X-ray energy diffraction (EDX) spectroscopy, thermal gravimetric analysis, elemental mapping, infrared spectroscopy (FT-IR), transmission electron microscope, and scanning electron microscope (FE-SEM) analysis were accomplished to acknowledge and investigate the effect of S and CuxO as active sites in heterogeneous catalyst to perform the reduction-nitro aromatic compounds reaction in the presence of CuxO@CS-400 as an effective heterogeneous catalyst. The studies showed that doping sulfur in the resulting carbon/metal oxide substrate increased the catalytic activity compared to the material without sulfur doping.

SnO2 nanoparticles: A recyclable and heterogeneous catalyst for Pechmann condensation of coumarins and Knoevenagel condensation-Michael addition of biscoumarins.

Recyclable SnO2 nanoparticles catalyze the Pechmann condensation between phenolic alcohols and ß-ketoesters at room temperature in ethanol leading to coumarins. Also, in another study the synthesis of biscoumarins catalyzed by SnO2 nanoparticles in the reaction between 4-hydroxycoumarin and aldehydes under same condition reactions. The corresponding coumarins and biscoumarins were produced efficiently with facility and excellent yields (93-98%). These approaches display the advantages of benign reaction conditions, non-chromatographic purification procedure, appropriate functional group tolerance and valuable process.

Organoselenium functionalized SBA-15 as a new catalyst for the cyanide-free conversion of oximes to nitriles.

BACKGROUND: Here we report a new selenium-based heterogeneous catalyst, which was prepared from the immobilization of diphenyl diselenide on amine-functionalized Santa Barbara Amorphous-15 (SBA-15). The catalyst characterization study has been confirmed by different analysis methods including Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction patterns (XRD), field-emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. RESULTS: The newly designed catalyst was successfully applied in the green dehydration reaction of oximes to corresponding nitriles in the presence of hydrogen peroxide/air. To demonstrate the role of the catalyst in this study, the model reaction was also carried out in the absence of the catalyst and a trace yield of the relevant product was achieved. CONCLUSION: In this way, a series of nitrile derivatives were obtained with 72-96% yields, also, the catalyst could be separated easily and recycled for four consecutive runs with no obvious drop in catalytic activity.

Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts.

The development of cost-effective, efficient, and novel catalytic systems is always an important topic for heterogeneous catalysis from academia and industrial points of view. Heteroatom-doped carbon materials have gained more and more attention as effective heterogeneous catalysts to replace metal-based catalysts, because of their excellent physicochemical properties, outstanding structure characteristics, environmental compatibility, low cost, inexhaustible resources, and low energy consumption. Doping of heteroatoms can tailor the properties of carbons for different utilizations of interest. In comparison to pure carbon catalysts, these catalysts demonstrate superior catalytic activity in many organic reactions. This review highlights the most recent progress in synthetic strategies to fabricate metal-free heteroatom-doped carbon catalysts including single and multiple heteroatom-doped carbons and the catalytic applications of these fascinating materials in various organic transformations such as oxidation, hydrogenation, hydrochlorination, dehydrogenation, etc.

Pd NPs supported on halloysite functionalized with Schiff base as an efficient catalyst for Sonogashira reaction.

A hybrid system was designed and synthesized through reacting modified halloysite (Hal-Cl) with Schiff base (DAB-PC) and applied as catalytic support for anchoring Pd NPs to afford Pd@Hal-DAB-PC catalyst. The resultant material was well identified by various analyses including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction patterns (XRD), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and inductively coupled plasma-optical emission spectrometry (ICP-OES) and revealed outstanding catalytic activity in the Sonogashira reaction in aqueous media. Also, This nanocatalyst was simply collected and recycled up to six runs with a slight drop in efficiency, indicating the durability of Pd@Hal-DAB-PC.

Diphenyl diselenide immobilized on magnetic nanoparticles: A novel and retrievable heterogeneous catalyst in the oxidation of aldehydes under mild and green conditions.

In the present study diselenide stabilized on silica coated Fe3O4 magnetic nano particles asa novel, highly efficient and magnetically retrievable heterogeneous catalyst was designed, synthesized and introduced. Full characterization of the newly prepared magnetic nanocatalyst was authenticated using several physico-chemical characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction patterns (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). Thereafter, the catalytic performance of this (Fe3O4@SiO2-Se)2 nanocatalyst was investigated in oxidation of aldehydes using H2O2 as the clean oxidant under aqueous conditions. Under the title conditions, a range of both aromatic and aliphatic aldehydes can be converted into the corresponding carboxylic acid products with excellent yields. Additionally, the magnetic nanoparticles could be conveniently recovered using an external magnetic field and reused four times without discernible decrease of efficiency. Some of the other outstanding features of this methodology are short reaction times, simple and easy work-up procedure, eco-friendly nature and cost effectiveness that make it economic, sustainable and in agreement with some green chemistry protocols.

Magnetic chitosan composite as a green support for anchoring diphenyl diselenide as a biocatalyst for the oxidation of sulfides.

Development of efficient, inexpensive and recyclable catalysts for a reaction under mild and green reaction conditions is still a very marvelous topic. In this work, diphenyl diselenide stabilized on magnetic chitosan as a novel, highly efficient, ecologically safe, cost-effective and magnetically recoverable heterogeneous nano-biocatalyst was prepared and characterized by different techniques, such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM). Then, the catalytic activity of resultant nano-biocatalyst was effectively appraised for the chemoselective oxidation of sulfides to sulfoxides using H2O2 as a green oxidant at ambient temperature with a good to high yields without use any organic solvents. Additionally, the easily preparation from cheap and commercially available reagent, carrying out the reactions in the eco-friendly and mild conditions, short reaction times, easy separation from reaction mixture, recoverability and reusability of catalyst for four consecutive cycles without a significant degradation in catalytic activity, are some prominent advantages of this novel catalyst. These advantages make it a potential candidate to address the industrial needs and economic and environmental concerns.