Magnetically Separable Nanocatalysts: Bridges between Homogeneous and Heterogeneous Catalysis

Short-Range Diffusion Enables General Synthesis of Medium-Entropy Alloy Aerogels

Medium-entropy alloy aerogels (MEAAs) with the advantages of both multimetallic alloys and aerogels are promising new materials in catalytic applications. However, limited by the immiscible behavior of different metals, achieving single-phase MEAAs is still a grand challenge. Herein, a general strategy for preparing ultralight 3D porous MEAAs with the lowest density of 39.3 mg cm^-3 among the metal materials is reported, through combining auto-combustion and subsequent low-temperature reduction procedures. The homogenous mixing of precursors at the ionic level makes the short-range diffusion of metal atoms possible to drive the formation of single-phase MEAAs. As a proof of concept in catalysis, as-synthesized Ni₅₀ Co₁₅ Fe₃₀ Cu₅ MEAAs exhibit a high mass activity of 1.62 A mg^-1 and specific activity of 132.24 mA cm^-2 toward methanol oxidation reactions, much higher than those of the low-entropy counterparts. In situ Fourier transform infrared and NMR spectroscopies reveal that MEAAs can enable highly selective conversion of methanol to formate. Most importantly, a methanol-oxidation-assisted MEAAs-based water electrolyzer can achieve a low cell voltage of 1.476 V at 10 mA cm^-2 for making value-added formate at the anode and H₂ at the cathode, 173 mV lower than that of traditional alkaline water electrolyzers.

Nanomagnetic macrocyclic Schiff-base-Mn(ii) complex: an efficient heterogeneous catalyst for click approach synthesis of novel β-substitued-1,2,3-triazoles

In the present work, a novel symmetrical 15-membered macrocyclic Schiff base complex of manganese was prepared using the reaction of the synthetic 2,6-diacetylpyridine functionalized Fe₃O₄ MNPs with 2,2-(piperazine-1,4-diyl)dianiline and Mn(ii) bromide salt via a template approach. The resulting [Fe₃O₄@PAM-Schiff-base-Mn][ClO₄] heterogenized complex was characterized using FT-IR, XRD, BET, TGA, EDX, Xray-mapping, SEM, TEM and VSM analysis. To demonstrate proof of concept, Huisgen 1,3-dipolar cycloaddition synthesis of 1,2,3-triazoles was selected to evaluate the activity and reusability of the catalyst. The ethanol as a green solvent proved to be an excellent reaction medium for this synthesis. Yields of up to 100% were obtained in some cases. Significantly, as demonstrated, [Fe₃O₄@PAM-Schiff-base-Mn][ClO₄] catalyst was recycled for 8 cycles without losing catalytic activity under the optimized reaction conditions. The hot filtration and ICP-OES tests ratified that there was no leaching of metal during the catalytic reaction, indicating the heterogeneous manner of the catalyst.

NiII NPs entrapped within a matrix of l-glutamic acid cross-linked chitosan supported on magnetic carboxylic acid-functionalized multi-walled carbon nanotube: a new and efficient multi-task catalytic system for the green one-pot synthesis of diverse heterocyclic frameworks

In the present study, a new l-glutamic acid cross-linked chitosan supported on magnetic carboxylic acid-functionalized multi-walled carbon nanotube (Fe3O4/f-MWCNT-CS-Glu) nanocomposite was prepared through a convenient one-pot multi-component sequential strategy. Then, nickelII nanoparticles (NiII NPs) were entrapped within a matrix of the mentioned nanocomposite. Afterward, the structure of the as-prepared Fe3O4/f-MWCNT-CS-Glu/NiII nanosystem was elucidated by various techniques, including FT-IR, PXRD, SEM, TEM, SEM-based EDX and elemental mapping, ICP-OES, TGA/DTA, and VSM. In the next part of this research, the catalytic applications of the mentioned nickelII-containing magnetic nanocomposite were assessed upon green one-pot synthesis of diverse heterocyclic frameworks, including bis-coumarins (3a-n), 2-aryl(or heteroaryl)-2,3-dihydroquinazolin-4(1H)-ones (5a-r), 9-aryl-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-diones (7a-n), and 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles (9a-n). The good-to-excellent yields of the desired products, satisfactory reaction rates, use of water solvent or solvent-free reaction medium, acceptable turnover numbers (TONs) and turnover frequencies (TOFs), along with comfortable recoverability and satisfying reusability of the as-prepared nanocatalyst for at least eight successive runs, and also easy work-up and purification procedures are some of the advantages of the current synthetic protocols.

Synthesis and application of novel urea-benzoic acid functionalized magnetic nanoparticles for the synthesis of 2,3-disubstituted thiazolidin-4-ones and hexahydroquinolines

In this work, we reported the synthesis and application of a new urea-benzoic acid containing ligand [(OEt)3Si(CH2)3-urea-benzoic acid] for the functionalization of silica coated magnetic nanoparticles. The resulting structure, namely Fe3O4@SiO2@(CH2)3-urea-benzoic acid, was characterized through different techniques including FT-IR, SEM, EDX-Mapping, VSM and TGA/DTG analysis. Then, Fe3O4@SiO2@(CH2)3-urea-benzoic acid was applied as a heterogeneous dual acidic and hydrogen bonding catalyst for the synthesis of 2,3-disubstituted thiazolidin-4-ones and hexahydroquinolines under mild and green reaction conditions. More importantly, all of the desired products were obtained with relatively good yields. Also, the catalyst was recovered and reused for four successive runs without significant reduction in yield of the model reaction.

Adsorption and photocatalytic properties of porphyrin loaded MIL-101 (Cr) in methylene blue degradation

In this study for the very first time, zinc tetraphenylporphyrin (ZnTPP) was loaded into MIL-101 (Zn[TPP]@MIL-101) to perform an adsorptive and photocatalytic dye removal. The physicochemical attributes of the catalyst were thoroughly determined by the usage of XRD, FTIR, FESEM, BET, UV-vis, and inductively coupled plasma (ICP). The obtained XRD pattern exhibited the phase purity of MIL-101 and its structural stability. The solid-phase diameter of the catalyst was observed to be ~ 270.76 ± 119.95 nm, while its gas adsorption data was indicative of a decrease in the specific surface area after the loading of ZnTPP. The ICP analysis displayed the amount of encapsulated Zn[TPP] (~ 17%) in MIL-101. The UV-vis confirmed the presence of Zn[TPP] in MIL-101 with the lack of any interferences or overlaps with the λ_max of methylene blue (MB) with the support. The dye removal of MB was investigated under dark conditions (adsorption) and UV light (photodegradation). The observed adsorption under dark conditions using Zn[TPP]@MIL-101 (99.27% yield) demonstrated a superior dye removal in comparison to the cases of photodegradation of MB by MIL-101 and Zn[TPP]@MIL-101 or adsorption by MIL-101. In conformity to the gathered results, [ZnTPP] was able to increase the adsorption capacity at pH = 7 at room temperature.

Stabilization of ruthenium on biochar-nickel magnetic nanoparticles as a heterogeneous, practical, selective, and reusable nanocatalyst for the Suzuki C-C coupling reaction in water

Waste recycling and the use of recyclable and available catalysts are important principles in green chemistry in science and industrial research. Therefore in this study, biochar nanoparticles were prepared from biomass pyrolysis. Then, they were magnetized with nickel nanoparticles to improve their recycling. Further, the magnetic biochar nanoparticles (biochar-Ni MNPs) were modified by dithizone ligand and then applied for the fabrication of a ruthenium catalyst (Ru-dithizone@biochar-Ni MNPs). This nanocatalyst was characterized by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), wavelength dispersive X-ray spectroscopy (WDX), N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM) techniques. The XRD studies of Ru in the nanocatalyst showed that the crystalline structure of ruthenium in the Ru-dithizone@biochar-Ni MNPs was hcp. Another principle of green chemistry is the use of safe and inexpensive solvents, the most suitable of which is water. Therefore, the catalytic activity of this catalyst was investigated as a practical, selective, and recyclable nanocatalyst in the Suzuki carbon-carbon coupling reaction in aqueous media. The VSM curve of this catalyst showed that it could be easily recovered using an external magnet, and recycled multiple times. Also, VSM analysis of the recovered catalyst indicated the good magnetic stability of this catalyst after repeated use.

Diverse and efficient catalytic applications of new cockscomb flower-like Fe3O4@SiO2@KCC-1@MPTMS@CuII mesoporous nanocomposite in the environmentally benign reduction and reductive acetylation of nitroarenes and one-pot synthesis of some coumarin compounds

In this research, Fe3O4@SiO2@KCC-1@MPTMS@CuII as a new cockscomb flower-like mesoporous nanocomposite was prepared and characterized by various techniques including Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), SEM-based energy-dispersive X-ray (EDX) spectroscopy, inductively coupled plasma-optical emission spectrometry (ICP-OES), thermogravimetric analysis/differential thermal analysis (TGA/DTA), vibrating sample magnetometry (VSM), UV-Vis spectroscopy, and Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses. The as-prepared Fe3O4@SiO2@KCC-1@MPTMS@CuII mesoporous nanocomposite exhibited satisfactory catalytic activity in the reduction and reductive acetylation of nitroarenes in a water medium and solvent-free one-pot synthesis of some coumarin compounds including 3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones) (namely, bis-coumarins) (3a-n) and 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles (6a-n) along with acceptable turnover numbers (TONs) and turnover frequencies (TOFs). Furthermore, the mentioned CuII-containing mesoporous nanocatalyst was conveniently recovered by a magnet from reaction environments and reused for at least seven cycles without any significant loss in activity, which confirms its good stability.

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

Sono and nano: A perfect synergy for eco-compatible Biginelli reaction

In this study, we evaluated the performance of nano-γ-Fe2O3–SO3H catalyst in the Biginelli reaction and synthesized 3,4-dihydropyrimidine-2-(1H)-ones. This reaction was carried out under solvent-free and ultrasonic irradiation conditions and belonged to one-pot multicomponent reactions (MCRs) with an adopted aromatic aldehyde, ethyl acetoacetate, and urea as starting materials for the beginning of the reaction. The synthesized materials were efficient in synthesizing 3,4-dihydropyrimidine-2-(1H)-ones via the Biginelli reaction under reaction conditions. Thus, the advantages of using nano-γ-Fe2O3–SO3H in the Biginelli reaction are short reaction time, high efficiency, green method, solvent free, and cost-effective. Furthermore, nano-γ-Fe2O3–SO3H as a heterogeneous catalyst can be recycled five times without significantly reducing catalytic activity.

Facile Synthesis of Silane-Modified Mixed Metal Oxide as Catalyst in Transesterification Processes

The fast depletion of fossil fuels has attracted researchers worldwide to explore alternative biofuels, such as biodiesel. In general, the production of biodiesel is carried out via transesterification processes of vegetable oil with the presence of a suitable catalyst. A mixed metal oxide has shown to be a very attractive heterogeneous catalyst with a high performance. Most of the mixed metal oxide is made by using the general wetness impregnation method. A simple route to synthesize silane-modified mixed metal oxide (CaO-CuO/C6) catalysts has been successfully developed. A fluorocarbon surfactant and triblock copolymers (EO)106(PO)70(EO)106 were used to prevent the crystal agglomeration of carbonate salts (CaCO3-CuCO3) as the precursor to form CaO-CuO with a definite size and morphology. The materials show high potency as a catalyst in the transesterification process to produce biodiesel. The calcined co-precipitation product has a high crystallinity form, as confirmed by the XRD analysis. The synthesized catalyst was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The mechanism of surface modification and the effects of the catalytic activity were also discussed. The biodiesel purity of the final product was analyzed by gas chromatography. The optimum biodiesel yield was 90.17% using the modified mixed metal oxide CaO-CuO/C6.

Thermal kinetic analysis of mustard biomass with equiatomic iron-nickel catalyst and its predictive modeling

Mustard waste briquettes are commercially used as a fuel for power production in boilers, whereas the thermal kinetics of the biomass plays a vital role in deciding the process parameters. The pyrolysis process converts biomass to value-added products such as biochar, bio-oil, and hydrocarbon gases based on the heating rates and temperature. To enhance the pyrolytic activity of mustard biomass, magnetically separable and reusable FeNi alloy catalyst is investigated. The thermo-conversion properties are studied under variable heating rates with 2 and 10% FeNi particles prepared through a facile chemical reduction technique. Thermal kinetics is computed using Flynn-Wall-Ozawa (FOW) and Kissinger-Akahira-Sunose (KAS) methods. The activation energies calculated using FOW and KAS methods increase with FeNi addition in mustard while the calorific value decreases. The FeNi alloy particles with the spike-like morphology provide better metal-biomass binding resulting in higher activation energy and facilitates the easy decomposition of lignin. The 10% FeNi -mustard shows uniform conversion independent of heating rates, suitable for magnetically recoverable catalytic pyrolysis. Response surface methodology analysis predicts optimum conversion for 10% FeNi added mustard and less significance for the heating rates in concurrence with the experiments. Artificial neural network utilized to predict and validate mass loss for mustard biomass exhibits best fit for the three neural hidden layer and one output layered topology.

Polymer microgels for the stabilization of gold nanoparticles and their application in the catalytic reduction of nitroarenes in aqueous media

Polymer microgels containing a polystyrene core and poly(N-isopropylmethacrylamide) shell were synthesized in aqueous media following a free radical precipitation polymerization. Au nanoparticles were fabricated into the shell region of the core–shell microgels denoted as P(STY@NIPM) by the in situ reduction of chloroauric acid with sodium borohydride. Various characterization techniques such as transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV-visible) and Fourier transform infrared spectroscopy (FTIR) were used for the characterization of Au–P(STY@NIPM). The catalytic potential of Au–P(STY@NIPM) toward the reductive reaction of 4-nitrophenol (4NP) under various reaction conditions was evaluated. The Arrhenius and Eyring parameters for the catalytic reduction of 4NP were determined to explore the process of catalysis. A variety of nitroarenes were converted successfully into their corresponding aminoarenes with good to excellent yields in the presence of the Au–P(STY@NIPM) system using NaBH₄ as a reductant. The Au–P(STY@NIPM) system was found to be an efficient and recyclable catalyst with no significant loss in its catalytic efficiency.

A core–shell microgel system was synthesized and used as a micro-reactor for the synthesis of gold nanoparticles. The resulting hybrid system has the ability to catalyze the reduction of various nitroarenes in aqueous media.

Preparation and Asymmetric Induction Evaluation of the First Ephedrine-Based Ligands Immobilized on Magnetic Nanoparticles

Herein, the synthesis and catalytic activity of two ephedrine-based catalysts and two ephedrine-based magnetic nanoparticle-supported catalysts are reported. All catalysts developed were tested in the addition of diethylzinc to aromatic aldehydes and in the Henry reaction. The homogeneous catalysts showed moderate catalytic activity in the organozinc addition and good activity in the Henry reaction, whereas in the case of the nanocatalyst, it was not effective in the addition of diethylzinc to aldehydes and gave reasonable results in the Henry reaction. Moreover, the nanocatalyst remained unchanged over the course of up to three catalytic cycles. To the best of our knowledge, the proposed system is the first recyclable ephedrine-based magnetic nanocatalyst employed in an enantioselective reaction.

A TEMPO-Functionalized Ordered Mesoporous Polymer as a Highly Active and Reusable Organocatalyst

The properties of high stability, periodic porosity, and tunable nature of ordered mesoporous polymers make these materials ideal catalytic nanoreactors. However, their application in organocatalysis has been rarely explored. We report herein for the first time the incorporation of a versatile organocatalyst, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), into the pores of an FDU-type mesoporous polymer via a pore surface engineering strategy. The resulting FDU-15-TEMPO possesses a highly ordered mesoporous organic framework and enhanced stability, and shows excellent catalytic activity in the selective oxidation of alcohols and aerobic oxidative synthesis of 2-substituted benzoxazoles, benzimidazoles and benzothiazoles. Moreover, the catalyst can be easily recovered and reused for up to 7 consecutive cycles.

Advanced Photocatalysts Based on Conducting Polymer/Metal Oxide Composites for Environmental Applications

Photocatalysts provide a sustainable method of treating organic pollutants in wastewater and converting greenhouse gases. Many studies have been published on this topic in recent years, which signifies the great interest and attention that this topic inspires in the community, as well as in scientists. Composite photocatalysts based on conducting polymers and metal oxides have emerged as novel and promising photoactive materials. It has been demonstrated that conducting polymers can substantially improve the photocatalytic efficiency of metal oxides owing to their superior photocatalytic activities, high conductivities, and unique electrochemical and optical properties. Consequently, conducting polymer/metal oxide composites exhibit a high photoresponse and possess a higher surface area allowing for visible light absorption, low recombination of charge carriers, and high photocatalytic performance. Herein, we provide an overview of recent advances in the development of conducting polymer/metal oxide composite photocatalysts for organic pollutant degradation and CO2 conversion through photocatalytic processes.

A novel superparamagnetic powerful guanidine-functionalized γ-Fe2O3 based sulfonic acid recyclable and efficient heterogeneous catalyst for microwave-assisted rapid synthesis of quinazolin-4(3H)-one derivatives in Green media

The novel organic–inorganic nanohybrid superparamagnetic (γ-Fe₂O₃@CPTMS–guanidine@SO₃H) nanocatalyst modified with sulfonic acid represents an efficient and green catalyst for the one-pot synthesis of quinazolin-4(3H)-one derivatives via three-component condensation reaction between anthranilic acid, acetic anhydride and different amines under microwave irradiation and solvent-free conditions (4a–q). XRD, FT-IR, FE-SEM, TGA, VSM and EDX were used to characterize this new magnetic organocatalyst. Outstanding performance, short response time (15–30 min), simple operation, easy work-up procedure, and avoidance of toxic catalysts can be regarded as its significant advantages. Moreover, it can be easily separated from the reaction solution through magnetic decantation using an external magnet, and recycled at least six times without notable reduction in its activity.

A novel organic–inorganic nanohybrid superparamagnetic nanocatalyst (γ-Fe₂O₃@CPTMS–guanidine@SO₃H) represents an efficient and green catalyst for the one-pot synthesis of quinazolin-4(3H)-one derivatives via a three-component condensation reaction.

Wet organic waste treatment via hydrothermal processing: A critical review

There are several recent reviews published in the literature on hydrothermal carbonization, liquefaction and supercritical water gasification of lignocellulosic biomass and algae. The potential of hydrochar, bio-oil or synthesis gas production and applications have also been reviewed individually. The comprehensive review on the hydrothermal treatment of wet wastes (such as municipal solid waste, food waste, sewage sludge, algae) covering carbonization, liquefaction and supercritical water gasification, however, is missing in the literature which formed the basis of the current review paper. The current paper critically reviews the literature around the full spectrum of hydrothermal treatment for wet wastes and establishes a good comparison of the different hydrothermal treatment options for managing wet waste streams. Also, the role of catalysts as well as synthesis of catalysts using hydrothermal treatment of biomass has been critically reviewed. For the first time, efforts have also been made to summarize findings on modelling works as well as techno-economic assessments in the area of hydrothermal treatments of wet wastes. The study concludes with key findings, knowledge gaps and future recommendations to improve the productivity of hydrothermal treatment of wet wastes, helping improve the commercial viability and environmental sustainability.

Synthesis of triarylpyridines with sulfonate and sulfonamide moieties via a cooperative vinylogous anomeric-based oxidation

Herein, novel magnetic nanoparticles with pyridinium bridges namely Fe3O4@SiO2@PCLH-TFA through a multi-step pathway were designed and synthesized. The desired catalyst and its corresponding precursors were characterized with different techniques such as Fourier transform infrared (FT-IR) spectroscopy, 1H NMR, 13C NMR, Mass spectroscopy, energy dispersive X-ray (EDX) analysis, thermogravimetric/derivative thermogravimetry (TG/DTG) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). In addition, the catalytic application of the prepared catalyst in the synthesis of new series of triarylpyridines bearing sulfonate and sulfonamide moieties via a cooperative vinylogous anomeric-based oxidation was highlighted. The current trend revealed that the mentioned catalyst shows high recoverability in the reported synthesis.

Reproducibility and Scalability of Magnetic Nanoheater Synthesis

The application of magnetic nanoparticles requires large amounts of materials of reproducible quality. This work explores the scaled-up synthesis of multi-core iron oxide nanoparticles through the use of thermal decomposition in organic media and kilograms of reagents. To this end, we check the effect of extending the high temperature step from minutes to hours. To address the intrinsic variability of the colloidal crystallization nucleation process, the experiments were repeated and analyzed statistically. Due to the simultaneity of the nuclei growth and agglomeration steps, the nanostructure of the samples produced was a combination of single- and multi-core nanoparticles. The main characteristics of the materials obtained, as well as the reaction yields, were analyzed and compared. As a general rule, yield, particle size, and reproducibility increase when the time at high temperature is prolonged. The samples obtained were ranked in terms of the reproducibility of different structural, colloidal, and magnetic features. The capability of the obtained materials to act as nanoheaters in magnetic hyperthermia was assessed, showing a strong dependence on the crystallite size (calculated by X-ray diffraction), reflecting the nanoparticle volume with a coherent magnetization reversal.

Preparation of Poly(ethylene glycol)@Polyurea Microcapsules Using Oil/Oil Emulsions and Their Application as Microreactors

The development process of catalytic core/shell microreactors, possessing a poly(ethylene glycol) (PEG) core and a polyurea (PU) shell, by implementing an emulsion-templated non-aqueous encapsulation method, is presented. The microreactors' fabrication process begins with an emulsification process utilizing an oil-in-oil (o/o) emulsion of PEG-in-heptane, stabilized by a polymeric surfactant. Next, a reaction between a poly(ethylene imine) (PEI) and a toluene-2,4-diisocyanate (TDI) takes place at the boundary of the emulsion droplets, resulting in the creation of a PU shell through an interfacial polymerization (IFP) process. The microreactors were loaded with palladium nanoparticles (NPs) and were utilized for the hydrogenation of alkenes and alkynes. Importantly, it was found that PEG has a positive effect on the catalytic performance of the developed microreactors. Interestingly, besides being an efficient green reaction medium, PEG plays two crucial roles: first, it reduces the palladium ions to palladium NPs; thus, it avoids the unnecessary use of additional reducing agents. Second, it stabilizes the palladium NPs and prevents their aggregation, allowing the formation of highly reactive palladium NPs. Strikingly, in one sense, the suggested system affords highly reactive semi-homogeneous catalysis, whereas in another sense, it enables the facile, rapid, and inexpensive recovery of the catalytic microreactor by simple centrifugation. The durable microreactors exhibit excellent activity and were recycled nine times without any loss in their reactivity.

Magnetically Isolable Pt0/Co3O4 Nanocatalysts: Outstanding Catalytic Activity and High Reusability in Hydrolytic Dehydrogenation of Ammonia Borane

The development of a new platinum nanocatalyst to maximize the catalytic efficiency of the precious noble metal catalyst in releasing hydrogen from ammonia borane (AB) is reported. Platinum(0) nanoparticles are impregnated on a reducible cobalt(II,III) oxide surface, forming magnetically isolable Pt⁰/Co₃O₄ nanocatalysts, which have (i) superb catalytic activity providing a record turnover frequency (TOF) of 4366 min^-1 for hydrogen evolution from the hydrolysis of AB at room temperature and (ii) excellent reusability, retaining the complete catalytic activity even after the 10th run of hydrolysis reaction. The outstanding activity and stability of the catalyst can be ascribed to the strong interaction between the platinum(0) nanoparticles and reducible cobalt oxide, which is supported by the results of XPS analysis. Pt⁰/Co₃O₄ exhibits the highest TOF among the reported platinum-nanocatalysts developed for hydrogen generation from the hydrolysis of AB.

Silica gel-immobilised chiral 1,2-benzenedisulfonimide: a Brønsted acid heterogeneous catalyst for enantioselective multicomponent Passerini reaction

A chiral heterogeneous catalyst derivative of (−)-4,5-dimethyl-3,6-bis(1-naphthyl)-1,2-benzenedisulfonimide is proven here to be efficient in a three-component asymmetric Passerini protocol, carried out in a deep eutectic solvent. Reaction conditions are mild and green, while enantioselectivity is excellent. The catalyst was easily recovered and reused with no decrease in its catalytic activity.

A chiral heterogeneous catalyst derivative of (−)-4,5-dimethyl-3,6-bis(1-naphthyl)-1,2-benzenedisulfonimide is proven here to be efficient in a three-component asymmetric Passerini protocol, carried out in a deep eutectic solvent.

A review on platinum(0) nanocatalysts for hydrogen generation from the hydrolysis of ammonia borane

This review reports a survey on the progress in developing highly efficient platinum nanocatalysts for the hydrolytic dehydrogenation of ammonia borane (AB). After a short prelude emphasizing the importance of increasing the atom efficiency of high cost, precious platinum nanoparticles (NPs) which are known to be one of the highest activity catalysts for hydrogen generation from the hydrolysis of AB, this article reviews all the available reports on the use of platinum-based catalysts for this hydrolysis reaction covering (i) early tested platinum catalysts, (ii) platinum(0) NPs supported on oxides, (iii) platinum(0) NPs supported on carbonaceous materials, (iv) supported platinum single-atom catalysts, (v) bimetallic- and (vi) multimetallic-platinum NP nanocatalysts, and (vii) magnetically separable platinum-based catalysts. All the reported results are tabulated along with the important parameters used in the platinum-catalyzed hydrolysis of AB. In the section "Concluding remarks and a look towards the future" a discussion is devoted to the approaches for making high cost, precious platinum catalysts as efficient as possible, ultimately lowering the cost, including the suggestions for the future research in this field.

A comprehensive survey upon diverse and prolific applications of chitosan-based catalytic systems in one-pot multi-component synthesis of heterocyclic rings

Heterocyclic compounds are among the most prestigious and valuable chemical molecules with diverse and magnificent applications in various sciences. Due to the remarkable and numerous properties of the heterocyclic frameworks, the development of efficient and convenient synthetic methods for the preparation of such outstanding compounds is of great importance. Undoubtedly, catalysis has a conspicuous role in modern chemical synthesis and green chemistry. Therefore, when designing a chemical reaction, choosing and or preparing powerful and environmentally benign simple catalysts or complicated catalytic systems for an acceleration of the chemical reaction is a pivotal part of work for synthetic chemists. Chitosan, as a biocompatible and biodegradable pseudo-natural polysaccharide is one of the excellent choices for the preparation of suitable catalytic systems due to its unique properties. In this review paper, every effort has been made to cover all research articles in the field of one-pot synthesis of heterocyclic frameworks in the presence of chitosan-based catalytic systems, which were published roughly by the first quarter of 2020. It is hoped that this review paper can be a little help to synthetic scientists, methodologists, and catalyst designers, both on the laboratory and industrial scales.

Pd nanoparticles loaded on modified chitosan-Unye bentonite microcapsules: A reusable nanocatalyst for Sonogashira coupling reaction

This work investigates the preparation of a catalytic complex of palladium nanoparticles supported on novel Schiff base modified chitosan-Unye bentonite microcapsules (Pd NPs@CS-UN). The complex has been characterized by FT-IR, EDS, XRD, TEM, HRTEM, Raman, ICP-OES and elemental mapping analyses. Pd NPs@CS-UN was used as a catalyst for Sonogashira coupling reactions between aryl halides and acetylenes, employing K₂CO₃ as the base and EtOH as a green solvent under aerobic conditions in which it showed high efficacy. Pd NPs@CS-UN was regenerated by filtration after the completion of the reaction. This catalytic process has many advantages including simple methodology, high yields, and easy work-up. The catalytic performance does not notably change even after five consecutive runs.

ZEUS (ZIF-based electrochemical ultrasensitive screening) device for isopentane analytics with focus on lung cancer diagnosis

Breath analytics is currently being explored for the development of point-of-care devices in non-invasive disease detection. It is based on the measurement of volatile organic compounds (VOCs) and gases that are produced by the body because of the metabolic pathways. The levels of these metabolites vary due to alteration in the endogenous oxidative stress-related metabolic pathways and can be correlated to understand the underlying disease condition. The levels of exhaled hydrocarbons in human breath can be used to design a rapid, easy to use method for lung cancer detection. This work outlines the development of an electrochemical sensing platform that can be used for the non-invasive diagnosis of lung cancer by monitoring isopentane levels in breath. This electrochemical sensor platform involves the use of [BMIM]BF4@ZIF-8 for sensing the target analyte. This synthesized nanocomposite offers advantages for gas sensing applications as it possesses unique properties such as an electrochemically active Room Temperature Ionic Liquid (RTIL) and a crosslinking Metal Organic Framework (MOF) that provides increased surface area for gas absorption. This is the first report of a hydrocarbon-based sensor platform developed for lung cancer diagnosis. The developed sensor platform displays sensitivity and specificity for the detection of isopentane up to 600 parts-per-billion. We performed structural and morphological characterization of the synthesized nanocomposite using various analytical techniques such as PXRD, FESEM, FTIR, and DLS. We further analyzed the electrochemical activity of the synthesized nanocomposite using a standard glassy carbon electrode. The application of the nanocomposite for isopentane sensing was done using a commercially available carbon screen printed electrode. The results so obtained helped in strengthening our hypothesis and serve as a proof-of-concept for the development of a breathomics-enabled electrochemical strategy. We illustrated the specificity of the developed nanocomposite by cross-reactivity studies. We envision that the detection platform will allow sensitive and specific sensing of isopentane levels such that it can used for point of care applications in noninvasive and early diagnosis of lung cancer, thereby leading to its early treatment and decrease in mortality rate.