The valorization of petroleum waste into high-performance catalytic materials is a major frontier of sustainable chemistry. This paper reports the preparation of a robust, highly active asphaltene oxide (AO) solid-acid catalyst via controlled oxidation with nitric acid. In contrast to the destructive Hummers approach, which results in a disastrous loss of carbon (16.58

To address the critical need to improve metal-support interactions and prevent palladium agglomeration in heterogeneous catalysis, this study reports a novel strategy for designing graphene oxide frameworks (GOFs) using tridentate organic linkers with varying heteroatom densities. Two palladium-functionalized nanocatalysts, Pd@GOF1 and Pd@GOF2, were successfully synthesized by cross-linking graphene oxide (GO) via amide formation with 1,3,5-tris(4-aminophenyl)benzene, and per-hydroxylated GO via esterification with nitrogen-rich 4,4′,4′′-s-triazine-1,3,5-triyltri-p-aminobenzoic acid, respectively. FT-IR analysis confirmed the successful framework assembly and the formation of N–Pd coordination bonds (at 530 cm⁻¹). Notably, Atomic Absorption Spectrometry (AAS) demonstrated that the nitrogen-dense triazine linker in GOF2 led to a significantly higher palladium loading of 31.92 wt

In the current study, a graphene organic framework (GOF-TDA) was successfully synthesized under mild conditions by cross-linking nanosheets of graphene oxide (GO) with 5-(4-nitrophenyl)-1,3,4-thiadiazol-2-amine (TDA) as the pillaring agent. The characterization of GOF-TDA has been conducted using various techniques, including FT-IR spectroscopy, FE-SEM, EDX, PXRD, TGA, and BET methods. The oxygenic functional groups in GO, the nitrogen atom in the amide groups, and the sulfur of the thiadiazole ring in TDA give mesoporous GOF-TDA a strong affinity for iodine molecules. This affinity occurs due to the formation of charge-transfer complexes between the host framework's oxygen, nitrogen, and sulfur atoms and the guest iodine molecules. Therefore, GOF-TDA demonstrated a high adsorption capacity of 835.2713 mg g-1 for uptaking iodine from a cyclohexane solution. Additionally, GOF-TDA also exhibited exceptional chemical, thermal, and structural stability towards iodine, with an excellent capacity of 153 wt% for volatile iodine. To the best of our knowledge, rare studies have specifically examined iodine uptake using a GOF constructed with a sulfur-based ligand, highlighting the importance of our research. This study also aimed to investigate the antibacterial properties of GOF-TDA (10 mg mL-1) against four species of bacteria, including two Gram-positive (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative (Escherichia coli and Pseudomonas aeruginosa). The results indicated that GOF-TDA was effective against all bacterial species, with noticeable growth inhibition in Gram-positive bacteria. Moreover, GOF-TDA demonstrated impressive growth inhibition and multiplication against two other Bacillus species, Bacillus tequilensis strain (T28) and Priestia endophytica (T25), from the initial hours of treatment as indicated by time-kill kinetic studies. Our study paves the way for the development of metal-free, eco-friendly, cost-effective, and stable multifunctional GOFs to meet critical needs in environmental protection and public health.

In the present study, a graphene organic framework (GOF-L-S) was successfully prepared by cross-linking nanosheets of graphene oxide (GO) with dimethyl-4,4 '-(methylenebis (2-thioxo-2,3-dihydro-1H-imidazole-3,1-diyl)) dibutyrate (L-S) as a pillaring agent via a transesterification process. GOF-L-S have been characterized by various analyses, such as Fourier transform infrared, BET, powder X-ray diffraction, energy-dispersive X-ray, thermogravimetric analysis, and FE-SEM. The oxygenic functional groups in GO and the sulfur atoms of L-S give mesoporous GOF-L-S a strong affinity for iodine molecules due to the formation of charge-transfer complexes between the host framework's sulfur and oxygen atoms and the guest iodine molecules. Therefore, GOF-L-S exhibited a high adsorption capacity of 1315.105 mg/g for removing iodine from the iodine/cyclohexane solution. In addition, GOF-L-S also displayed extraordinary stability toward iodine, with an excellent capacity of 232 wt % for volatile iodine. To the best of our knowledge, this is the first report aiming at iodine uptake with a GOF built on a thioamide-based ligand. This study also aimed to investigate the antibacterial properties of GOF-L-S. The antibacterial activity of GOF-L suspensions (80 mu g/mL) was tested against four species of bacteria, including two Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and two Gram-positive (Bacillus subtilis, Staphylococcus aureus). The results indicated that the GOF-L-S were effective against all bacterial species, with especially remarkable growth inhibition against Gram-positive bacteria. In addition, GOF-L-S demonstrated promising results in controlling antibiotic-resistant strains of E. coli and S. aureus in the environment. This study will contribute to the development of a cost-effective, metal-free, stable, and environmentally friendly multifunctional framework for the remediation of iodine-containing pollutants and the control of bacterial infections, addressing critical needs in environmental protection and public health.

A novel chelating adsorbent was successfully synthesized by cross-linking of 4, 4', 4''-s-triazine-1, 3, 5-triyltri-p-aminobenzoic acid as a linker with nanosheets of graphene oxide to provide a 3-dimensional framework. Therefore, the adsorption process of Cd+2 and Pb+2 on the adsorbent was investigated by employing an ultrasonic bath. The optimum condition containing the small amount of adsorbent (10 mg) for both metals at pH=8 for Cd+2 and pH=5 for Pb+2, and a short time of two minutes caused gaining an absorption capacity at a high level. The presence of nitrogen-functionalized groups in the porous Graphene Oxide Framework (GOF) contributed to the absorption of lead and cadmium ions. The kinetic models of pseudo-first-order and pseudo-second-order were used to define the kinetic process. The experimental adsorption datum was properly suited to the kinetic model of the pseudo-second-order (R-2 = 0:990). It indicated that adsorbing ions of heavy metals onto GOF happens through a chemical process, and adsorption isotherms of Cd+2 and Pb+2 ions were in high-grade accordance with the Longmuir model. Eventually, because of the rapid adsorption kinetics, high removal capacity, perfect stability, and being reusable, this GOF can be used as a remediation adsorbent with high-performing heavy metals removal from aqueous solutions. (c) 2023 Sharif University of Technology. All rights reserved.

A 3D framework was effectively created by cross-linking graphene oxide nanosheets with 2,5-bis(((3-mercaptopropyl)dimethoxysilyl)oxy)terephthalohydrazide as a sulfur-containing linker, resulting in a successful synthesis of a novel chelating adsorbent. The resulting material showed remarkable efficiency in removing Hg2+ ions from polluted water, with a high adsorption capacity of 204.08 mg g−1 at pH 6 and 25 °C. The adsorption process followed a monolayer model described by the Langmuir isotherm, and the kinetics followed a pseudo-second-order model, indicating a chemical adsorption mechanism. The material demonstrated rapid adsorption and desorption, maintaining its performance even after multiple regeneration cycles. Overall, the synthesized 3D GOF stands out as an exceptional adsorbent due to its porous structure, efficient chelating functional groups, and robust efficacy in eliminating Hg2+ ions from contaminated water sources.

Benzimidazole functionalized mesoporous silica nanoparticles immobilized Pd(0)/Pd(II) has been proposed as an efficient catalyst for the one-pot preparation of biaryls via Suzuki–Miyaura cross-coupling reaction and for reduction of nitro-arenes to aromatic amines. Firstly, mesoporous silica nanoparticles (MSNs) were prepared by using soft template strategy. After template removal and subsequent functionalization by 3-aminopropyl trimethoxy silane (APS), further grafting was achieved via terephthalaldehyde (ALD) and 2-aminobenzimidazole (BzIm). Lastly palladium chloride was added to prepare the nanocatalyst. MSN-APS-ALD-BzIm-Pd has been characterized by Fourier-transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) surface area analysis, powder X-Ray diffraction (PXRD), energy dispersive X-ray analysis, high-resolution transmission electron microscopy, field emission scanning electron microscope, thermogravimetric analysis, X-Ray photoelectron spectroscopy and Inductively coupled plasma-optical emission spectroscopy (ICP-OES). After successful characterization, MSN-APS-ALD-BzIm-Pd was evaluated as a nanocatalyst in Suzuki–Miyaura cross-coupling reaction and in reduction of nitroarenes. According to the obtained results, both processes are performed in a short time and with high turnover frequency (TOF) and efficiency. Other advantages include heterogeneous and recyclable catalyst, green reaction conditions, small amounts of catalyst, facile work-up and user-friendly procedure.

3-Chloropropyltrimethoxysilane (CPTMS) was grafted on the surface of silica coated Fe3O4 core (Fe3O4@MCM-41) and then condensed with thiocarbohydrazide (TCH) to obtain Fe3O4@MCM-41-CPS-TCH. Then the heterogeneous Fe3O4@MCM-41-CPS-TCH-Pd nanocatalyst was synthesized by adding palladium(II) chloride to functionalized Fe3O4@MCM-41. The resultant nanomaterials were characterized using several techniques such as FT-IR, XRD, FE-SEM, HRTEM, EDS, BET, VSM, XPS, AAS and TGA. Then, the efficiency of this Palladium based magnetic nanocomposite was examined as catalyst for the preparation of biaryl derivatives using the Suzuki coupling of phenylboronic acid with various aryl halides in H2O/EtOH as a green solvent. The as-synthesized nanocomposite was also checked for the Heck–Mizoroki coupling reaction of various aryl halides and styrene. This catalytic system was easily retrieved by a magnetic field and reused for several times without distinct reduction in catalytic activity.

A new method was developed for producing a catalyst involving a Pd nanoparticle (NP) embedded in a graphene oxide framework (Pd@GOF) with ordered macro‐ and mesoporous structures. First, 5,5′‐diamino‐2,2′‐bipyridine was selected as cross‐linking for covalent modification of GO nanosheets to prepare a three‐dimensional (3D) framework with interlayer spaces in which well‐dispersed and ultra‐small Pd NPs in situ grew and embedded the framework. The synthesized nanopores 3D Pd@GOF can act as nanoreactors to help the reaction substrates thoroughly come into contact with the surface of Pd NPs, thereby exhibiting high activity toward the Heck reaction, rarely reported concerning Pd NPs supported on one‐side functionalized graphene. The Pd@GOF catalyst can be used 10 times without any significant loss in the catalytic activity, confirming the long‐term stability of this catalyst. Therefore, the covalently assembled GOF was proposed as a universal platform for hosting noble metal NPs to construct the desired metal@GOF nanocatalyst with improved activity and stability that can be used in a broad range of practical applications.

Magnetic mesoporous silica nanocomposite, Fe3O4@MCM-41, was prepared and functionalized with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS). Then Schiff base grafted nanoparticles were synthesized by the condensation of 5,5'-methylene bis (salicylaldehyde) and then benzhydrazide with Fe3O4@MCM-41-AEAPS. Finally, by adding Cu (CH3COOH)(2).H2O, the magnetic nanoparticles (MNPs) functionalized with Cu (II) Schiff base complex were synthesized. The new organic-inorganic hybrid nanocomposite was characterized by FT-IR, PXRD, AAS, BET, TGA, VSM, FE-SEM, HRTEM and EDX techniques. Then, the performance of this copper based magnetic nanocatalyst was investigated for the synthesis of 5-substituted 1H-tetrazole derivatives using one pot three-component reactions of various aldehydes, hydroxyl amine hydrochloride and sodium azide. The catalyst can be easily isolated from the reaction mixture by applying an external magnet and reused for at least 5 times without significant loss in catalytic activity. Also, the antibacterial activity of the streptomycin loaded magnetic nanoparticles against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria in the presence and absence of a magnetic field were studied. Results revealed that when these materials exposed to the magnetic field, bacteriostatic activity of nanocomposites was increased. Furthermore, the enzyme immobilization ability of the synthesized compounds was investigated and the results showed that these nanoparticles efficiently immobilized amylase enzyme.

A series of heteroleptic mononuclear cyclopalladated benzo[h]quinolinate complexes of general formula [Pd(bzq)(Ph2PCH2PPh2C(H)C(O)C6H4-p-R)ClO4 (bzq = 7,8-benzoquinoline; R = Cl (C-1), Br (C-2), NO2 (C-3), OCH3(C-4)), were synthesized by the reaction of [Pd(bzq)(mu-Cl)](2) with 0.5 equiv of phosphorus ylides [Ph2PCH2PPh2C(H)C(O)C6H4-p-R] in CH2Cl2 solvent at room temperature. Bridge splitting with stabilized phosphorus ylides afforded new mononuclear palladacycle derivatives with two five-membered rings. The formation of the complexes was ascertained by elemental analysis, IR, UV-visible and NMR spectroscopic methods. All of the complexes exhibited absorption bands at high energy due to the intraligand transitions [(IL)-I-1 pi ->pi*] and absorptions at lower energy, which are attributed to MLCT transition [(Pd,4d) pi ->pi* (bzq)]. The influence of the R substituent and different solvents on the UV-visible absorption of all complexes was also investigated. Furthermore, palladacycle C-3 was employed as an efficient catalyst in the Suzuki-Miyaura coupling reactions of various aryl halides and phenylboronic acids in the mixed EtOH/H2O media. (C) 2020 Elsevier Ltd. All rights reserved.

Magnetic mesoporous silica nanocomposite, Fe3O4-MCM-41, was functionalized with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS) and then condensed with 5,5′-methylene bis(salicylaldehyde), followed by N(4)-phenylthiosemicarbazide to produce a ONS Schiff base grafted nanocomposite. Finally, by adding palladium(II) acetate, the palladium Schiff base complex was immobilized on magnetic nanocomposite. The characterization of new nanocomposites was carried out by means of several techniques such as FT-IR, XRD, FE-SEM, HRTEM, EDS, BET, VSM, XPS, DRS and TGA. The new nanocatalyst, Fe3O4@MCM-41-SB-Pd, was used in synthesis of symmetrical and unsymmetrical biaryl compounds via the Suzuki–Miyaura cross-coupling of phenylboronic acid with aryl halides. This catalyst was easily recovered by applying an external magnetic field and reused for several times without significant loss of its catalytic activity. Also the ability of synthesized mesoporous nanocomposites for enzyme immobilization was investigated and results showed that they efficiently immobilized α-amylase enzyme.

In the present study, nickel nanoparticles (Ni-NPs) immobilized on graphene oxide-chitosan (GO-Chit-Ni) have been synthesized and characterized as a catalyst for reduction of nitroarenes in water. For this purpose, GO has been functionalized with chitosan (GO-Chit). Then, Ni-NPs were immobilized on the surface of GO-Chit using a simple method. The GO-Chi-Ni nanocomposites were characterized using Fourier Transforms Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), X-Ray Diffraction Measurements (XRD), and Atomic Adsorption Spectrometry (AAS). The GO-Chi-Ni nanoparticles demonstrated appropriate catalytic activity in reducing nitroarenes to aryl amines in the existence of sodium borohydride (NaBH4) aqueous solution as a hydrogen source at 80oC. This catalytic system applies environmentally benign water as a solvent that is cheap, easily accessible, non-toxic, non-volatile, non-flammable and thermally stable. This type of catalyst can be applied several times with no considerable change in its performance.

In this work, graphene oxide was functionalized with chitosan (GO-Chit) followed by a simple approach for immobilization of palladium nanoparticles onto a chitosan grafted graphene oxide surface. The Pd-nanocomposite (GO-Chit-Pd) was characterized using Transmission Electron Microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) measurements. The catalytic activity of the prepared heterogeneous graphene oxide functionalized chitosan-palladium (GO-Chit-Pd) was investigated in term of C-N coupling reaction (Buchwald-Hartwig amination reaction of aryl halides) yielding products of N-arylamines. The easy purification, convenient operation, and environmental friendliness, combined with a high yield, render this method viable for use in both laboratory research and larger industrial scales. Studying the reusability of the catalyst in this work showed that it could be reused for five times without obvious loss in catalytic activity.

A very simple and efficient procedure for the preparation of primary amides is described from carboxylic acids using Mukaiyama reagent/KNCO in aqueous acetonitrile. Availability of the reagents, simplicity, and easy workup of the reaction crude make this method attractive for organic chemists.

Graphene oxide was functionalized with chitosan for palladium immobilization (GO–Chit–Pd), which was used as an efficient catalyst for the reduction of aromatic nitro compounds using sodium borohydride in water. To achieve the best catalytic efficacy, various parameters such as temperature, solvent, mole ratio of hydrogen sources, and the amount of catalyst were optimized. The method has been applied to the reduction of a broad range of nitroarenes with different properties. The easy purification, convenient operation, environmental friendliness, and high product yields render this method viable for use. The nanocatalyst can be easily separated and efficiently recovered and reused for multiple cycles without appreciable loss in its catalytic activity.

The nitration of aromatic compounds is one of the most important industrial processes and is the subject of a large body of literature. In this study, the use of N-bromosuccinimide in the presence of NaNO2 and wet SiO2 as a mild and safe method was studied for the nitration of aromatic compounds. These reactions occur under mild, neutral and heterogenic conditions. This system can be applied to a wide range of acid-sensitive substrates in comparison to traditional methods.

Graphene oxide was functionalized with benzimidazole for palladium immobilization. The resultant graphene–benzimidazole-supported palladium composite (G-BI-Pd) was characterized using infrared and Raman spectroscopies, transmission electron microscopy and energy-dispersive X-ray spectroscopy. G-BI-Pd showed excellent catalytic activity and fast reaction kinetics in the aqueous-phase Suzuki–Miyaura reaction of aryl iodides and bromides with phenylboronic acid under relatively mild conditions (5–25 min, 80 °C). The catalyst can be used several times without any significant loss of its catalytic activity.

Background: A rapid and efficient synthesis of amides via Beckmann rearrangement of ketoximes with good to excellent yields has been carried out using Mukaiyama reagent/Et3N system. The procedure is mild and suitable for both aromatic and cycloaliphatic substrates affording the products in good to quantitative yields with short reaction times.Methods: A suspension of acetophenone oxime (0.135 g, 1 mmol), Mukaiyama reagent (0.383 g, 1.5 mmol), and Et3N (0.21 mL, 1.5 mmol) in CH3CN (3 mL) was magnetically stirred at room temperature. After completion of the reaction (monitored by TLC) and evaporation of CH3CN, aqueous HCl (5%, 10 mL) was added and the organic layer extracted with CH2Cl2 (3 x 5 mL). The combined organic extracts were dried over Na2SO4, filtered, and concentrated. Purification of the crude product by short column chromatography on silica gel (n-hexane/EtOAc, 5/2) provided N-phenylacetamide (0.120 g, 89%) as a white solid: mp 112 degrees C (lit. 113-115 degrees C); 1 H NMR (CDCl3, 250 MHz) 8.03 (brs, 1H), 7.52 (d, J= 8.0 Hz, 2H), 7.28 (t, J= 7.8 Hz, 2H), 7.09 (t, J= 7.4 Hz, 1H), 2.15 (s, 3H).Results: In a continuation of our studies on the use of the Mukaiyama reagent in organic transformations, we became interested in evaluating it as a reagent in the presence of triethylamine as a base for the conversion of ketoximes into corresponding N-substituted amides under mild conditions. To optimize the reaction conditions and find the best base and solvent using benzophenone oxime as a model substrate, a few experiments were carried out with Mukaiyama reagent and various bases and solvents at room temperature. The optimum conditions of reaction involved benzophenone oxime (1 mmol), Mukaiyama reagent (1.5 mmol), triethylamine (1.5 mmol), CH3CN (3 mL) at room temperature. Under the optimized conditions, a series of N-substituted amides were studied to establish the scope and limitations of this method. A wide range of substituted ketoximes derived from various aromatic, cycloaliphatic, and heterocyclic ketoximes gave desired products in good to excellent yields.Conclusion: We have disclosed a mild procedure for obtaining amides from the corresponding ketoximes via Beckmann rearrangement using Mukaiyama reagent. Among the attractive features of this protocol are its use of inexpensive and commercially available reagent, mild reaction conditions, simplicity, general applicability, relatively short reaction time, high yield and good selectivity.

The combination of the Mukaiyama reagent and sodium nitrite in the presence of wet SiO2 was found to be an effective system for the conversion of amines into N-nitrosamines and hydrazines into azides. The heterogeneous reaction proceeded in good to excellent yields and possesses advantages such as the use of non-hazardous reagents, and simple reaction work-up.