Microporous hierarchically Zn-MOF as an efficient catalyst for the Hantzsch synthesis of polyhydroquinolines

2D Cerium-Organic Frameworks as an Efficient Heterogeneous Catalyst for the Synthesis of 1,4-Dihydropyridines via Hantzsch Reaction

Herein, a new two-dimensional (2D) Ce-organic frameworks (referred to as SLX-4) was achieved by traditional solvothermal conditions. Initial studies of SLX-4 toward Hantzsch reaction showed that good catalytic activity can be obtained under mild conditions, giving the desired 1,4-dihydropyridines in moderate to high yields. The catalyst could be reused at least 4 times keeping good catalytic activity. Moreover, compared to the previously reported MOFs catalysts for Hantzsch reactions, SLX-4 was stable in most acidic and basic environment, and gave comparable yield.

Zr-based metalloporphyrin MOF probe for electrochemical detection of parathion-methyl

An electrochemical (EC) sensor based on metalloporphyrin metal-organic framework (MOF) for the detection of parathion-methyl (PM) has been developed. The prepared MOF-525(Fe) exhibits great signal enhancement toward the electrochemical detection of PM owing to its unique structural properties and electrochemical activities. Under optimal experimental conditions, the as-prepared MOF-525(Fe) based EC sensor exhibited excellent PM sensing performance with a wide linear detection range (0.1 μM-100 μM) and low limit of detection (LOD, 1.4 nM). Compared to its corresponding Fe metalloporphyrin (linker), MOF-525(Fe) exhibited a superior sensitivity (28.31 μA cm-2·μM-1), which is 3.7 times higher than the sensitivity of FeTCPP linker (7.56 μA cm-2·μM-1) towards PM. The improved performance is associated with the high specific surface area and the large pore channels of MOF-525(Fe) facilitating a better interaction between PM and the Fe metalloporphyrin active sites, especially in the lower concentration range. Moreover, a possible affinity of the PM molecules toward Zr6 clusters may also contribute to the selective enrichment of PM on MOF-525(Fe). This EC sensor further demonstrated high selectivity in the presence of interfering molecules. The recovery results further confirm accurate PM sensing in actual samples, which suggests promising applications for the rapid detection of environmental organophosphates by metalloporphyrin MOFs.

Magnetic BiFeO3 nanoparticles: a robust and efficient nanocatalyst for the green one-pot three-component synthesis of highly substituted 3,4-dihydropyrimidine-2(1H)-one/thione derivatives

In this research, magnetic bismuth ferrite nanoparticles (BFO MNPs) were prepared through a convenient method and characterized. The structure and morphological characteristics of the prepared nanomaterial were confirmed through analyses using Fourier-transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), elemental mapping, powder X-ray diffraction (XRD), N2 adsorption-desorption isotherms and vibrating sample magnetometry (VSM) techniques. The obtained magnetic BFO nanomaterial was investigated, as a heterogeneous Lewis acid, in three component synthesis of 3,4-dihydropyrimidin-2 (1H)-ones/thiones (DHPMs/DHPMTs). It was found that the BFO MNPs exhibit remarkable efficacy in the synthesis of various DHPMs as well as their thione analogues. It is noteworthy that this research features low catalyst loading, good to excellent yields, environmentally friendly conditions, short reaction time, simple and straightforward work-up, and the reusability of the catalyst, distinguishing it from other recently reported protocols. Additionally, the structure of the DHPMs/DHPMTs was confirmed through 1H NMR, FTIR, and melting point analyses. This environmentally-benign methodology demonstrates the potential of the catalyst for more sustainable and efficient practices in green chemistry.

Dual-State Red-Emitting Zinc-Based MOF Accompanied by Dual-Mode and Dual-State Detection: Color Tonality Visual Mode for the Detection of Tetracycline

Red-emitting metal-organic frameworks (MOFs) are still mostly based on the use of lanthanides or functionalization with red fluorophores. However, production of transition-metal-based MOFs with red-emitting is scarce. This work reports on the synthesis of a novel dual-state red-emitting Zn-based MOF (denoted as UoZ-7) with the capability to detect target molecules in dual state, in solution, and as solid on paper. UoZ-7 gives strong red emission when excited in the solution and in the solid state with 365 nm ultraviolet (UV) lamp irradiation. Coordination-induced emission is the mechanism for the red emission enhancement in the MOF as a restriction of intramolecular rotation occurred to the ligand within the framework structure. UoZ-7 was successfully used for tetracycline (TC) using dual-mode detection, fluorescence-based ratiometry, and color tonality, in the dual state, in solution, and on the paper. TC molecules adsorb on the red-emitting UoZ-7 surface, and a yellow-greenish color emerges due to aggregation-induced emission between TC and UoZ-7. Concurrently, the inner filter effect diminishes the red emission of UoZ-7. The dual-mode or dual-state detection platform provides a simple and reliable fast method for the detection of TC on-site in various environmental and biomedical applications. Moreover, red-emitting UoZ-7 will have further luminescence-based biomedical applications.

Postsynthetic Modification of Amine-Functionalized MIL-101(Cr) Metal-Organic Frameworks with an EDTA-Zn(II) Complex as an Effective Heterogeneous Catalyst for Hantzsch Synthesis of Polyhydroquinolines

The present work aims at preparing the EDTA-Zn(II) complex-supported on the amine-functionalized MIL-101(Cr) MOF-as a new and effective heterogenized catalyst. The optimization of the hydrothermal process shows that 120 °C is the best condition to grow the MIL-101(Cr)-NH2 MOF crystals. Moreover, regarding the use of the postsynthetic modification (PSM) method, hexadentate EDTA was grafted on this support via a simple aminolysis process before further coordinating it with Zn ions to create the corresponding Zn(II) catalytic complex. The catalytic activity of this compound was then investigated in the context of a one-pot synthesis of polyhydroquinolines. This approach has a number of advantages including the following: the use of a solvent that is not hazardous, applying a porous catalyst that is inexpensive, secure, and recyclable; rapid reaction times, high levels of efficiency, and the simplicity of MOF catalyst separation. Accordingly, the process in question can be given the label of "green chemistry".

Chitosan-based GOx@Co-MOF composite hydrogel: A promising strategy for enhanced antibacterial and wound healing effects

A novel composite hydrogel was synthesized via Schiff base reaction between chitosan and di-functional poly(ethylene glycol) (DF-PEG), incorporating glucose oxidase (GOx) and cobalt metal-organic frameworks (Co-MOF). The resulting CS/PEG/GOx@Co-MOF composite hydrogel was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and energy-dispersive X-ray spectroscopy (EDS). The results confirmed successful integration and uniform distribution of Co-MOF within the hydrogel matrix. Functionally, the hydrogel exploits the catalytic decomposition of glucose by GOx to generate gluconic acid and hydrogen peroxide (H2O2), while Co-MOF gradually releases metal ions and protects GOx. This synergy enhanced the antibacterial activity of the composite hydrogel against both Gram-positive (S. aureus) and Gram-negative bacteria (E. coli), outperforming conventional chitosan-based hydrogels. The potential of the composite hydrogel in treating wound infections was evaluated through antibacterial and wound healing experiments. Overall, CS/PEG/GOx@Co-MOF hydrogel holds great promise for the treatment of wound infections, paving the way for further research and potential clinical applications.

Synthesis of hydrazone-based polyhydroquinoline derivatives - antibacterial activities, α-glucosidase inhibitory capability, and DFT study

In recent years, polyhydroquinolines have gained much attention due to their widespread applications in medicine, agriculture, industry, etc. Here, we synthesized a series of novel hydrazone-based polyhydroquinoline derivatives via multi-step reactions. These molecules were characterized by modern spectroscopic techniques (1H-NMR, 13C NMR, and LC-HRMS) and their antibacterial and in vitro α-glucosidase inhibitory activities were assessed. Compound 8 was found to be the most active inhibitor against Listeria monocytogenes NCTC 5348, Bacillus subtilis IM 622, Brevibacillus brevis, and Bacillus subtilis ATCC 6337 with a zone of inhibition of 15.3 ± 0.01, 13.2 ± 0.2, 13.1 ± 0.1, and 12.6 ± 0.3 mm, respectively. Likewise, compound 8 also exhibited the most potent inhibitory potential for α-glucosidase (IC50 = 5.31 ± 0.25 μM) in vitro, followed by compounds 10 (IC50 = 6.70 ± 0.38 μM), and 12 (IC50 = 6.51 ± 0.37 μM). Furthermore, molecular docking and DFT analysis of these compounds showed good agreement with experimental work and the nonlinear optical properties calculated here indicate that these compounds are good candidates for nonlinear optics.

Fabricating pentaazatetraethylene modified sulfonated polyacrylamide for dye adsorption from aqueous media: isotherms and kinetics models

In this study, pentaazatetraethylene-modified sulfonated polyacrylamide (PAm-SO3-N5) was synthesized and used as a novel efficient adsorbent to remove calmagite from aqueous media. To this end, a central composite design (CCD) was applied to reduce the number of reaction variables (i.e., adsorbent concentration, temperature, initial concentration, and pH) on calmagite removal. The results showed that calmagite was entirely adsorbed by the PAm-SO3-N5 within 30 min. In addition, a pseudo-second-order (PSO) model was prepared as the optimum formula to fit the kinetics information. The modeling results revealed that film diffusion and adsorption are rate-limiting stages to remove the dyes. Using a Langmuir isotherm to fit the equilibrium data, the highest equilibrium adsorption was calculated to be 1732.5 mg/g. In the present study, the ΔH value indicates that the adsorption is of chemical type. Also, the negative sign of ΔS° shows that PAm-SO3-N5 removes calmagite during a relatively stable process with randomness in the system. The increase in ΔG° values with increasing temperature indicates a descending trend in the feasibility degree of calmagite adsorption. Eventually, recycling the adsorbent for 7 cycles to adsorb calmagite dye showed no remarkable activity loss.

Laser-Driven Rapid Synthesis of Metal-Organic Frameworks and Investigation of UV-NIR Optical Absorption, Luminescence, Photocatalytic Degradation, and Gas and Ion Adsorption Properties

In this study, we designed a platform based on a laser-driven approach for fast, efficient, and controllable MOF synthesis. The laser irradiation method was performed for the first time to synthesize Zn-based MOFs in record production time (approximately one hour) compared to all known MOF production methods with comparable morphology. In addition to well-known structural properties, we revealed that the obtained ZnMOFs have a novel optical response, including photoluminescence behavior in the visible range with nanosecond relaxation time, which is also supported by first-principles calculations. Additionally, photocatalytic degradation of methylene blue with ZnMOF was achieved, degrading the 10 ppm methylene blue (MB) solution 83% during 1 min of irradiation time. The application of laser technology can inspire the development of a novel and competent platform for a fast MOF fabrication process and extend the possible applications of MOFs to miniaturized optoelectronic and photonic devices.

Significance of Zn Complex Concentration on Microstructure Evolution and Corrosion Behavior of Al/WS2

Corrosion is a harmful processes which by definition is a chemical or electrochemical reaction between a substance (usually a metal) and the environment which leads to a change in the properties of the substance and has destructive effects. In this study, new composites consisting of Al/WS2/ZnTerp-2TH with 5 and 10 wt.% ZnTerp-2TH were prepared and the results were fully compared. Al/WS2 played the role of matrix and ZnTerp-2TH played the role of reinforcement. In other words, as a novelty to prevent the corrosion of Al/WS2, ZnTerp-2TH is designed and synthesized and showed good results when the corrosion ratio was reduced by the existence of ZnTerp-2TH. Furthermore, the NMR and mass analysis of ZnTerp-2TH were carried out, and the thermal properties, X-ray diffraction, Fourier-transform infrared (FTIR) spectroscopy, morphology, energy-dispersive X-ray spectroscopy (EDX) analysis and corrosion behavior of the composites were also discussed in detail. The crystal size values of composites were calculated by the modified Scherrer method 34, 26 and 27 nm for Al/WS2, Al/WS2/5 wt.% ZnTerp-2TH and Al/WS2/10 wt.% ZnTerp-2TH, respectively. The microstructural examination of the specimens showed that the reinforcing phase (ZnTerp-2TH) has a favorable distribution on the surface of Al/WS2 when it covers the cracks and holes. In addition, the corrosion investigation results showed that the addition of ZnTerp-2TH to Al/WS2 can improve the corrosion resistance when the Ecorr and Icorr values of Al/WS2/10 wt.% ZnTerp-2TH were recorded in tandem -724 mV/decade and 5 uA cm-2.

Amino-induced cadmium metal-organic framework based on thiazole ligand as a heterogeneous catalyst for the epoxidation of alkenes

Selective epoxidation of olefins is of high interest in the chemical industry due to the many applications of epoxides. This study reports on the synthesis of Cd-MOF, [Cd(DPTTZ)(5-AIP)] (IUST-1) (where DPTTZ = 2, 5-di (pyridine-4-yl) thiazolo [5, 4-d] thiazole, 5-AIP = 5-Aminoisophthalic acid), by a reflux method, which can be considered as a fast and simple process. The morphology and structure of the synthesized IUST-1 were determined by using FE-SEM (Field Emission Scanning Electron Microscopy), EDX (Energy Dispersive Analysis of X-ray), Mapping (Elemental Mapping), CHNS (Elemental analysis), XRD (X-Ray Diffraction), FT-IR (Fourier Transform Infrared), and TGA (Thermo Gravimetric Analysis). The epoxidation of cyclooctene was investigated using the activity of catalytic IUST-1. The results showed that in the presence of tert-butyl hydroperoxide and CCl4 in a 1:2 alkene/oxidant ratio, a high epoxide yield (99.8%) was obtained. In addition, IUST-1 can be easily separated by simple filtration and recycled five times successfully with a slight decrease in activity. This compound has some advantages such as high yield, short reaction time, and ease of reuse, which make it a suitable heterogeneous catalyst for the epoxidation of cyclooctene.

Marine carrageenan‐based NiO nanocatalyst in solvent‐free synthesis of polyhydroquinoline derivatives

This study presents the preparation of nickel oxide nanoparticles (NiO NPs) in the presence of marine seaweed kappa‐carrageenan (κ‐carrageenan) polysaccharide as a green stabilizer and coating agent under optimal conditions. Thermal gravimetric analyzer (TGA) and Fourier transform infrared (FTIR) results revealed thermal stability and the presence of functional groups of κ‐carrageenan‐coated NiO (NiO@κ‐Car) NPs. The color change of the solution from green to black and advent peak at 320 nm primitively confirmed the formation of NiO NPs. Further, transmission electron microscopy (TEM) images of NiO@κ‐Car demonstrate rather irregular spherical and cubic morphology, showing an average size of 18 ± 1.5 nm. Further, X‐ray diffraction (XRD) analysis confirms that NiO NPs appear as cubic crystal structures with a crystallite size of 23.7 nm. According to the turnover number (TON) and turnover frequency (TOF) results, green NiO@κ‐Car exhibits superior catalytic efficiency in one‐pot multicomponent synthesis of polyhydroquinoline derivatives under free‐solvent conditions. Hydrogen‐1 (1H) and carbon‐13 (13C) nuclear magnetic resonance (NMR) spectra indicated the successful synthesis of various organic products. The key advantages of the proposed efficient synthetic protocol include reusability of the catalyst (four runs), simple workout, high yield of the products, environmental sustainability, and solvent‐free reaction condition. A possible mechanism was also suggested, indicating the role of NiO@κ‐Car as a proficient heterogeneous nanocatalyst in the reaction.

A sustainable protocol for selective alcohols oxidation using a novel iron-based metal organic framework (MOF-BASU1)

The selective oxidation of active and inactive alcohol substrates is a highly versatile conversion that poses a challenge in controlling the functionality and adjustments on MOFs. On the other hand, it offers an attractive opportunity to expand their applications in designing the next generation of catalysts with improved performance. Herein, a novel iron-based MOF containing sulfonamide (MOF-BASU1) has been fabricated by the reaction of 1,3-benzene disulfonylchloride linker and FeCl3·6H2O. Based on the results, the active surface area of the synthesized MOF is large, which highlights its unique catalytic activity. Optimum conditions were reached after 0.5-2 h, with 15 mg loading of the synthesized MOF under optimal conditions. Furthermore, the turnover frequency was 18-77.6 h-1, which is comparable to values previously reported for this process. Overall, the high catalytic activity observed for MOF-BASU1 might be because of the obtained high surface area and the Lewis acidic Fe nodes. Furthermore, the MOF-BASU1 revealed a remarkable chemoselectivity for aldehydes in the presence of aliphatic alcohols. Overall, the high product yields, facile recovery of nanocatalysts, short reaction times, and broad substrate range make this process environmentally friendly, practical, and economically justified.

Green synthesis of thiourea derivatives from nitrobenzenes using Ni nanoparticles immobilized on triazine-aminopyridine-modified MIL-101(Cr) MOF

Nanohybrid metal-organic frameworks (MOF) have recently been considered next-generation catalysts regarding their unique features like large surface-to-volume ratio, tailorable geometry, uniform pore sizes, and homogeneous distribution of active sites. In this report, we address the triazine-aminopyridine-modified 3D Cr-centred MOF MIL-101(Cr)-NH2 following a post-synthetic modification approach. The excellent chelating ability of triazine-aminopyridine was applied to immobilize Ni ions over the host matrix MOF. The as-synthesized material was physicochemically characterized using various analytical techniques like FT-IR, electron microscopy, EDS, elemental mapping, XRD, and ICP-OES. Subsequently, the material has been catalytically employed in synthesizing new thiourea derivatives by reacting to nitrobenzene derivatives and phenyl isocyanate. The catalyst was isolated by centrifugation and recycled in 6 consecutive runs without momentous loss of its reactivity.

Ultrasound-Promoted preparation and application of novel bifunctional core/shell Fe3O4@SiO2@PTS-APG as a robust catalyst in the expeditious synthesis of Hantzsch esters

In this work, D-(-)-α-phenylglycine (APG)-functionalized magnetic nanocatalyst (Fe₃O₄@SiO₂@PTS-APG) was designed and successfully prepared in order to implement the principles of green chemistry for the synthesis of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives under ultrasonic irradiation in EtOH. After preparing of the nanocatalyst, its structure was confirmed by different spectroscopic methods or techniques including Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermal gravimetric analysis (TGA). The performance of Fe₃O₄@SiO₂@PTS-APG nanomaterial, as a heterogeneous catalyst for the Hantzsch condensation, was examined under ultrasonic irradiation and various conditions. The yield of products was controlled under various conditions to reach more than 84% in just 10 min, which indicates the high performance of the nanocatalyst along with the synergistic effect of ultrasonic irradiation. The structure of the products was identified by melting point as well as FTIR and ¹H NMR spectroscopic methods. The Fe₃O₄@SiO₂@PTS-APG nanocatalyst is easily prepared from commercially available, lower toxic and thermally stable precursors through a cost-effective, highly efficient and environmentally friendly procedure. The advantages of this method include simplicity of the operation, reaction under mild conditions, the use of an environmentally benign irradiation source, obtaining pure products with high efficiency in short reaction times without using a tedious path, which all of them address important green chemistry principles. Finally, a reasonable mechanism is proposed for the preparation of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives in the presence of Fe₃O₄@SiO₂@PTS-APG bifunctional magnetic nanocatalyst.

CuI nanoparticle-immobilized on a hybrid material composed of IRMOF-3 and a sulfonamide-based porous organic polymer as an efficient nanocatalyst for one-pot synthesis of 2,4-diaryl-quinolines

As a significant class of synthetic and natural products with multiple biological activities, quinolines are used in medical and electronic devices. In this study, a novel method is presented to synthesize 2,4-diarylquinoline derivatives via a simple one-pot multicomponent reaction between phenylacetylenes, aniline derivatives, and aldehydes in CH₃CN using IRMOF-3/PSTA/Cu. Notably, polymer/MOF is stabilized through a reaction between a sulfonamide-triazine-based porous organic polymer [poly (sulfonamide-triazine)](PSTA) and an amino-functionalized zinc metal-organic framework (IRMOF-3). Next, the prepared nanocomposites (IRMOF-3/PSTA) are modified using copper iodide nanoparticles (CuI NPs). Overall, the high product yields, facile recovery of nanocatalysts, short reaction times, and broad substrate range make this process environmentally friendly, practical, and economically justified.

Sequential Assembly and Stabilization of Cu6S6 Octahedral Clusters in NaCl-, NiAs-, and CdI2-Related Structures and Their Utility toward Thermochromism and Multicomponent Hantzsch Reaction

Seven new inorganic-organic coordination polymer compounds have been synthesized and their structures are determined by single-crystal structure determination. The compounds were prepared by the sequential assembly of a [Cu₆(mna)₆]^6- moiety in the presence of a Mn salt and a secondary amine ligand. Of the seven compounds, [{Cu₆(mna)₆}Mn₃(H₂O)(H₂O)_1.5]·5.5H₂O (I), [{Cu₆(mna)₆}Mn₃(H₂O)(Im)_1.5]·3.5H₂O (Ia), [{Cu₆(mna)₆}{Mn(BPY)(H₂O)}₂{Mn(H₂O)₄}]·2H₂O (III), and [{Cu₆(mna)₆}{Mn(BPE)_0.5(H₂O)₂}₂{Mn(BPE)(H₂O)₂}] (IV) have a three-dimensional structure, whereas [{Cu₆(mna)_4.5(Hmna)_1.5}{Mn(BPA)(H₂O)₂}{Mn(H₂O)}]{Mn_0.25(H₂O)₃}·7H₂O (II), [{Cu₆(mna)₆}{Mn(4-BPDB)_0.5H₂O}{Mn(H₂O)₂}].{Mn(H₂O)₆}·6H₂O (V), and [{Cu₆(mna)₄(Hmna)₂}·{Mn(H₂O)₃}₂]·(4-APY)₂·6H₂O (VI) have a two-dimensional structure. Some of the prepared compounds exhibit structures that closely resemble the classical inorganic structures, such as NaCl (Ia, III), NiAs (I), and CdI₂ (IV and VI). The stabilization of such simple structures from the assembly of octahedral Cu₆S₆ clusters and different Mn species and aromatic nitrogen-containing ligands suggests the subtle interplay between the constituent reactants. The compounds were examined for the multicomponent Hantzsch reaction, which gave the product in good yields. The compounds, II and VI, on heating to 70 °C change color reversibly from pale yellow to deep red, which suggests the possible use of these compounds as thermochromic materials. The present study suggests that the Cu₆S₆ octahedral clusters can be assembled into structures that resemble classical inorganic structures.

Synthesis of a new magnetic metal organic framework based on nickel for extraction of carvacrol and thymol in thymus and savory samples and analyzed with gas chromatography

The present research aims at reporting a new sorbent, a magnetic nano scale metal-organic framework (MOF), based on nickel acetate and 6-phenyl-1,3,5-triazine-2,4-diamine. The prepared sorbent was used to extract carvacrol and thymol using an ultrasonic-assisted dispersive micro solid phase extraction (UA-DμSPE) method. The structure of the metal organic framework was studied by applying scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectrometry (EDS), and vibrating sample magnetometer (VSM). The effects of various parameters such as ionic strength of sample solution, amount of sorbent (mg), volume of eluent solvent (μL), vortex and ultrasonic times (min) were optimized. Under optimal conditions, the analytes resulted in determination coefficients (R ²) of 0.9985 and 0.9967 in the concentration range 0.01-2 μg mL^-1, and in limits of detection of 0.0025 and 0.0028 μg mL^-1. Significantly, this method can be successfully applied in order to determine the target analytes in spiked real samples. Notably, the relative mean recoveries range from 94.5 to 105.7%.

Phosphomolybdic acid hydrate encapsulated in MIL-53 (Fe): a novel heterogeneous heteropoly acid catalyst for ultrasound-assisted regioselective nitration of phenols

In this study, a heterogeneous catalyst, PMA@MIL-53 (Fe) (MIL ⇒ Matériaux de l'Institut Lavoisier), has been used to replace the usual mineral acids such as sulfuric acid. A wide variety of nitration methods require the use of a mixture of acids such as concentrated nitric acid and sulfuric acid, which result in producing a large amount of acidic waste. During recent years, the use of the heterogeneous system for the nitration of aromatic compounds has been highly considered and used by chemists due to some specific advantages, i.e. easy separation of the product from the reaction mixture, the possibility of recycling and reusing the catalyst, etc. Herein, the catalyst was synthesized using a metal-organic framework and a heteropoly phosphomolybdic acid. The PMA@MIL-53 (Fe) was prepared using a similar method of MIL-53 (Fe) synthesis. Afterwards, FeCl3·6H2O and 1,4-benzene dicarboxylic acid (BDC) in a dimethylformamide solution were placed in an ultrasound bath and, then, HPA (heteropoly acid) was added to the reaction mixture. The PMA (phosphomolybdic acid) encapsulation in MIL-53 (Fe) was confirmed using various analysis. Under optimal conditions, the catalytic activity of PMA@MIL-53 (Fe) was evaluated in nitration of phenol under ultrasonic waves. Besides, the ratio of the two products of ortho and para was obtained using GC. Optimum conditions were reached after 15 minutes, in such a way that the loaded PMA was 0.02 g under optimal conditions, the efficiencies of ortho-nitrophenol and para nitrophenol were 54.98 and 45.01, respectively.

Ni(ii) immobilized on poly(guanidine-triazine-sulfonamide) (PGTSA/Ni): a mesoporous nanocatalyst for synthesis of imines

Mesoporous materials have been the subject of intense research regarding their unique structural and textural properties and successful applications in various fields. This study reports a novel approach for synthesizing a novel porous polymer stabilizer through condensation polymerization in which Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) are used as hard templates. Using this method allowed the facile and fast removal of the template and mesopores formation following the Fe3O4 MNPs. Different techniques were performed to characterize the structure of the polymer. Based on the obtained results, the obtained mesoporous polymeric network was multi-layered and consisted of repeating units of sulfonamide, triazine, and guanidine as a novel heterogeneous multifunctional support. Afterward, the new nickel organometallic complex was supported on its inner surface using the porous poly sulfonamide triazine guanidine (PGTSA/Ni). In this process, the obtained PGTSA/Ni nanocomposite was used as a heterogeneous catalyst in the synthesis of imines from amines. Since this reaction has an acceptorless dehydrogenation pathway, the hydrogen gas is released as its by-product. The synthesized nanocatalyst was structurally confirmed using different characterization modalities, including FT-IR, SEM, XRD, EDX, TEM, elemental mapping, ICP-AES, BET, and TGA. In addition, all products were obtained in high turnover frequency (TOF) and turnover number (TON). The corresponding results revealed the high selectivity and activity of the prepared catalyst through these coupling reactions. Overall, the synthesized nanocatalyst is useable for eight cycles with no considerable catalytic efficiency loss.

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.

Chlorosulfonic acid coated on porous organic polymer as a bifunctional catalyst for the one-pot three-component synthesis of 1,8-naphthyridines

The synthesis of six-membered oxygen- and nitrogen-containing heterocycles has been regarded as the most fundamental issue in organic chemistry and the chemical industry because these heterocycles are used in producing high-value products. In this study, an efficient, economic, sustainable, and green protocol for their multicomponent synthesis has been developed. The one-pot direct Knoevenagel condensation-Michael addition-cyclization sequences for the transformation of aromatic aldehydes, malononitrile, and 2-aminopyridine generate the corresponding 1,8-naphthyridines over a novel mesoporous bifunctional organocatalyst supported cholorosulfonic acid [poly(triazine-benzene sulfonamide)-SO3H (PTBSA-SO3H)] under ambient conditions. The catalyst was used for the formation of 1,8-naphthyridine derivatives for six runs. The current strategy provided a wider substrate range, and short reaction times.

The use of metal-organic frameworks as heterogeneous catalysts

This article presents an overview of some of the available research studies of MOFs as catalysts. Catalytic studies of magnetic iron oxide nanoparticles with modified surfaces, MOFs with precious metals such as palladium, platinum, and silver, with zirconium, hafnium, copper, alkaline earth metals, lanthanides are generalized. The studies of the catalytic activity of micro- and mesoporous MOF structures are described.

Silica sulfuric acid coated on SnFe2O4 MNPs: synthesis, characterization and catalytic applications in the synthesis of polyhydroquinolines

An efficient and heterogeneous novel magnetic solid sulfuric acid, immobilized on silica functionalized SnFe₂O₄, was successfully synthesized, characterized, and employed as a novel recoverable nanocatalyst for the synthesis of biologically active polyhydroquinoline derivatives. The SnFe₂O₄@SiO₂-SO₃H was easily synthesized and confirmed using various spectroscopic techniques, including FT-IR, XRD, EDX, Map, TGA, SEM and TEM analyses. The catalytic behavior of the resulting catalyst system was investigated in the Hantzsch synthesis of polyhydroquinoline derivatives. The desired products were obtained with high conversions and excellent reusability.