Efficient Heterogeneous Catalyst Research Articles

Promotion of Single-Electron Transfer by Low-Coordinated Co Single Atoms to Facilitate Advanced Oxidation Processes in Wastewater Treatment.

Heterogeneous catalysts are fascinating for advanced oxidation processes (AOPs) in wastewater treatment to reduce cost, metal contamination, and pH operation limitations. However, they usually encounter low catalytic efficiency because of the difficult single-electron-transfer (SET) pathway during AOPs. Herein, an efficient heterogeneous catalyst for AOPs is realized through the rational regulation of N coordination around Co single-atom (SA) centers in favor of SET. As guided by calculations, low N coordination enables a high density of electronic states at the Fermi energy level of SA Co to facilitate SET activation of peroxomonosulfate (PMS). A special oxide-compounding method is further applied to decrease the N coordination of SA Co on the carbon carriers from common Co1-N3/4 to the desired Co1-N2. Co1-N2 shows a delightful activity for AOP degradation of various organic pollutants with kinetic rate and turnover frequency values up to 0.862 min-1 and 389 h-1, respectively, greatly outperforming those of Co1-N3/4. It is also superior in a wide pH operation range and has strong resistance to environmental disturbances. Detailed mechanistic investigations confirm the generation of singlet oxygen (1O2) instead of common radical O species from the SET between PMS and Co1-N2, corroborating the calculated results and accounting for the enhanced AOP activity.

Precise Single‐Atom Modification of Hybrid Lead Chlorides for Electron Donor‐Acceptor Effect and Enhanced Photocatalytic Aerobic Oxidation

Hybrid lead halides show significant potential in photocatalysis due to their excellent photophysical properties, but the atomically precise modification of their organic component to achieve synergistic interactions with the lead halide units remains a great challenge. Herein, for the first time, we have employed the crystal engineering strategy to construct a class of single‐atom‐substituted hybrid lead halides with electron donor‐acceptor (D‐A) effect. The lead halide frameworks consist of 1D linear [PbCl]+ chains as inorganic building units and benzoxadiazole/benzothiadiazole/ benzoselenadiazole‐funtionalized dicarboxylates as linkers. The covalent bonding between the organic ligands with electron‐withdrawing groups and the electron‐rich lead halide units not only facilitate the charge separation, but also enhance structural robustness that is critical for photocatalysis. The D‐A structured lead halides serve as highly efficient heterogeneous photooxidation catalysts, including aerobic oxidation of C(sp3)‐H bonds, oxidative coupling of primary amines, oxidation of phenylboronic acids and selective oxidation of sulfides that are demonstrated in 30 examples. Importantly, these photooxidation reactions are able to be driven by natural sunlight and ambient air to afford quantitative yields. Moreover, our lead halide photocatalysts are successful to fix into a photocatalytic flow system, which enables the flow‐type synthesis of high value‐added photooxidation products on a gram scale.

Precise Single-Atom Modification of Hybrid Lead Chlorides for Electron Donor-Acceptor Effect and Enhanced Photocatalytic Aerobic Oxidation.

Hybrid lead halides show significant potential in photocatalysis due to their excellent photophysical properties, but the atomically precise modification of their organic component to achieve synergistic interactions with the lead halide units remains a great challenge. Herein, for the first time, we have employed the crystal engineering strategy to construct a class of single-atom-substituted hybrid lead halides with electron donor-acceptor (D-A) effect. The lead halide frameworks consist of 1D linear [PbCl]+ chains as inorganic building units and benzoxadiazole/benzothiadiazole/ benzoselenadiazole-funtionalized dicarboxylates as linkers. The covalent bonding between the organic ligands with electron-withdrawing groups and the electron-rich lead halide units not only facilitate the charge separation, but also enhance structural robustness that is critical for photocatalysis. The D-A structured lead halides serve as highly efficient heterogeneous photooxidation catalysts, including aerobic oxidation of C(sp3)-H bonds, oxidative coupling of primary amines, oxidation of phenylboronic acids and selective oxidation of sulfides that are demonstrated in 30 examples. Importantly, these photooxidation reactions are able to be driven by natural sunlight and ambient air to afford quantitative yields. Moreover, our lead halide photocatalysts are successful to fix into a photocatalytic flow system, which enables the flow-type synthesis of high value-added photooxidation products on a gram scale.

Intensification of n-butyl ethanoate synthesis using ultrasound over ammonium sulphate supported on silica extracted from rice husk ash as an efficient heterogeneous catalyst

ABSTRACT The silica extracted from rice husk ash was used as support to load ammonium sulphate ((NH4)2SO4) (10–40 wt.%) and ammonium sulphate supported on rice husk silica ((NH4)2SO4/RHS) catalysts were characterised by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and scanning electron microscope (SEM) with EDS techniques. The catalyst was further used to convert butan-1-ol to n-butyl ethanoate in an ultrasonic batch reactor. The study demonstrated the influence of ultrasound and operating parameters on the conversion. The maximum conversion of 88.77% was attained at the optimal operating conditions of temperature 353 K, molar ratio 1:2 (ethanoic acid to butan-1-ol), catalyst loading 4% (w/w), duty cycle 75% and ultrasound power 80 W. When compared with the conventional process, the reaction time was reduced by 54% in ultrasound-assisted synthesis over conventional synthesis. It has been observed that intensification benefits as it lowers reaction time for the ultrasound-assisted approach.

One-pot synthesis of porous carbon nanospheres supported CuPd alloy catalysts for the hydrogenation-dechlorination of 2,3,6-trichloropyridine

Hydrogenation-dechlorination to produce 2,3-dichloropyridine is important for the next-generation pesticides. In this work, we successfully synthesized porous carbon nanospheres supported CuPd alloy nanoparticles via a simple and efficient one-pot strategy. Furthermore, by adjusting the Cu/Pd ratio and carbonization temperature, the obtained Cu2Pd1@PCNs-500-H2O2 showed the highly catalytic activity for the hydrogenation-dechlorination of 2,3,6-trichloropyridine with a conversion rate of 70.1 % and selectivity of 71.2 %. The catalyst showed outstanding catalysis performance even after five cycles. This simple and rapid one-pot strategy provides a new approach for the large-scale synthesis of efficient heterogeneous catalysts and offers an effective solution for reducing the high costs associated with precious metals.

Using In situ Transmission Electron Microscopy to Study Strong Metal-Support Interactions in Heterogeneous Catalysis.

Precisely controlling the microstructure of supported metal catalysts and regulating metal-support interactions at the atomic level are essential for achieving highly efficient heterogeneous catalysts. Strong metal-support interaction (SMSI) not only stabilizes metal nanoparticles and improves their resistance to sintering but also modulates the electrical interaction between metal species and the support, optimizing the catalytic activity and selectivity. Therefore, understating the formation mechanism of SMSI and its dynamic evolution during the chemical reaction at the atomic scale is crucial for guiding the structural design and performance optimization of supported metal catalysts. Recent advancements in in situ transmission electron microscopy (TEM) have shed new light on these complex phenomena, providing deeper insights into the SMSI dynamics. Here, the research progress of in situ TEM investigation on SMSI in heterogeneous catalysis is systematically reviewed, focusing on the formation dynamics, structural evolution during the catalytic reactions, and regulation methods of SMSI. The significant advantages of in situ TEM technologies for SMSI research are also highlighted. Moreover, the challenges and probable development paths of in situ TEM studies on the SMSI are also provided.

Kinetics, thermodynamics, and optimization studies using response surface methodology in quinoxalines synthesis with efficient heterogeneous catalysts: environmental sustainability metrics assessment

Kinetics, thermodynamics, and optimization studies using response surface methodology in quinoxalines synthesis with efficient heterogeneous catalysts: environmental sustainability metrics assessment

Rational Assembly of Three-component Coordination Polymers as Heterogeneous Catalysts for CO2 Cycloaddition and Cyanosilylation Reactions.

Four new coordination polymers based on 5-(((1H-imidazol-2-yl)methyl)amino) isophthalic acid (H3L) and auxiliary ligands (1,10-phenanthroline, 2,2'-bipyridine, and 4,4'-bipyridine), namely, {[Zn(HL)(phen)(H2O)]·2H2O}n (CP 1), {[Ni(HL)(phen)(H2O)]}n (CP 2), {[Ni(HL)(2,2'-bpy)(H2O)]·2H2O}n (CP 3) and {[Cd(HL)(4,4'-bpy)0.5(H2O)]·2H2O}n (CP 4) were rationally assembled. Furthermore, these four CPs were screened as heterogeneous catalysts for CO2 cycloaddition and cyanosilylation reactions under mild conditions. The catalytic experiments showed that CP 1 had the better catalytic performance, excellent substrate tolerance and recyclability for the above two reactions. It is speculated that the excellent activity of CP 1 may be due to the open Lewis base site and the Lewis acidic characteristics of the zinc (II) center. After five cycles, the catalytic activities of CP 1 did not significantly decrease, and the structures remained unchanged. Therefore, the CP 1 was considered efficient and stable heterogeneous catalysts for above the two reactions.

Sulfonated reduced graphene oxide (rGO-SO3H): A green, sustainable and efficient heterogeneous catalyst for synthesis of pyrazole containing 1,4 dihydropyridine derivatives

A simple mild, efficient, expeditious and straightforward synthetic methodology has been established toward furnishing of therapeutically important structurally diverse multi-heterocyclic pyrazole containing substituted 1,4-dihydropyridine (1,4-DHP's) derivatives which might be valuable heterocyclic compound because of the existence of pharmaceutically and medicinally important 1,4-dihydropyridine (1,4-DHP) and pyrazole entities. In this reported synthetic strategy, sulfonated reduce graphene oxide was firstly reported as a highly efficient heterogenous carbo-catalyst for one-pot 4-C synthesis of pyrazole based 1,4-dihydropyridine (DHPs) derivatives. The reported sulfonated reduce graphene oxide (rGO-SO3H) offered mild reaction conditions, structural diversity, high atom economy, operational simplicity, high product conversion, high yield (96%) with wide range of substrates within 15–20 min in ethanol at refluxing temperature. Additionally, experiment results revealed that synthesized carbo-catalyst can be recycled and reused efficiently for at least five reaction cycles. All the synthesized compounds were characterized by IR, HRMS, 1H NMR and 13C NMR, spectroscopic techniques.

Anchoring of Ni(II)-Schiff base complex in surface modified SBA-15: A reusable and efficient heterogeneous catalyst for nitroaromatic reduction

A newly designed Ni(II) dimeric Schiff-base complex [NiL] has been synthesized with our earlier reported ligand. Here, the aim is to study the catalytic activity of [NiL] towards reduction of nitroarenes by using NaBH4.Various physicochemical techniques were employed to characterize the complex, [NiL] including single-crystal X-ray diffraction. The homogeneous complex [NiL] exhibited superior catalytic efficiency, prompting its selection for the development of a recyclable heterogeneous catalyst. This was done by immobilizing it over a surface-modified SBA-15 functionalized with 3-aminopropyl group. The resulting SBA-15@APTES@NiL (SBNi) catalyst was thoroughly characterised by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Powder X-ray Diffraction and N2 adsorption analysis, which suggested successful immobilization of the nickel complex on the solid support. This heterogeneous catalyst demonstrated stability in both organic and aqueous medium, facilitating the reduction of nitroarenes in presence of NaBH4. A pseudo first order reaction was observed with a rate constant value 0.09617 min-1 and correlation parameter (R2) 0.9735 for the nitrophenol reduction in presence of high concentration of NaBH4. Additionally, the surface-modified catalyst allowed for easy separation through filtration. The catalyst retained recyclability up to five cycles without any significant change in catalytic activity.

1-Dimensional metal Nitride-Supported platinum nanoclusters for Low-Temperature hydrogen production from formic acid

Formic acid is widely recognized as a suitable liquid hydrogen carrier for linking renewable energies toward various economic sectors. Designing efficient and stable heterogeneous catalysts for low-temperature hydrogen generation from formic acid is vital for this topic. In this study, a rational hierarchical architecture is explored by assembling Pt nanoclusters with 1-dimensional (1D) GaN nanowires. The catalytic architecture describes a considerable hydrogen production activity of 54.89 mmol·gcat−1·h−1 with a nearly 100 % selectivity and a turnover frequency (TOFPt) of 505.7 h−1 under near ambient condition, enables the achievement of a high turnover number of 306,981 mol H2 per mole Pt over 200 h of long-term operation. Through comprehensive mechanistic studies, it is unraveled that the synergistic effect between Pt nanoclusters and GaN significantly reduces the energy barrier for the formation of the key HCOO* intermediate from formic acid dehydrogenation whereas significantly increase the energy barrier of HCOOH → HCO* + *OH. It thus simultaneously contributes to improving the activity and selectivity of formic acid decomposition toward H2. This study proposes a promising strategy for hydrogen generation from formic acid at low temperatures, which is critical for achieving carbon neutrality by coordinating industrial waste heat with renewable energies via liquid hydrogen carriers.

Facile fabrication of Cu/kaolin nanocomposite as highly efficient heterogeneous catalyst for 4-nitrophenol reduction in aqueous solution

Hazardous organic pollutants in industrial wastewaters are becoming a major global challenge that threatens life on earth and particularly poses a serious health risk to human beings. 4-Nitrophenol (4-NP) is a highly hazardous organic contaminant that has been extensively utilized across multiple industries, and their wastewater disposal into water streams leads to a higher accumulation of 4-NP. It is therefore important for both academia and industry to make catalysts that are cheap, very effective, good for the environment, easy to recover, and can be used more than once for reducing 4-NP in normal conditions. This paper reports the synthesis, characterization, and application of Cu/kaolin nanocomposite (NC) as an efficient heterogeneous catalyst for decomposing 4-NP, a model organic molecule. The catalyst was synthesized by incorporating a copper precursor into layered kaolin clay and directly reducing the metal precursor using sodium borohydride (NaBH4). The morphology, structure, surface property, and interaction of the resulting Cu/kaolin NC were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron spectroscopy/energy-dispersive X-ray spectroscopy, selected area electron diffraction, X-ray diffraction, and N2 adsorption/desorption, and the results clearly demonstrated the growth of copper nanoparticles on the kaolin surface. It was discovered that the Cu nanoparticles (NPs) on the kaolin surface had a crystallite size of about 23.6 nm. The significance of Cu NPs and the high catalytic activity of the synthesized Cu/kaolin NC toward 4-NP reduction by NaBH4 were evaluated by the catalytic reduction experiments. Among the different nanocomposites synthesized, 30-Cu/kaolin showed the highest catalytic activity for 4-NP reduction, with a reduction efficiency of over 99 % within 4 min with a pseudo-first-order rate constant, kapp, of 1.23 min−1. Furthermore, the reusability test indicated that Cu/kaolin NC can be reused for up to six runs efficiently without significant decrease in its catalytic performance, indicating the nanocomposite has excellent stability and great potential applications in industrial and agricultural wastewater treatment.

Photo-Fenton-like activity of Fe/ZnO structure applied as a heterogeneous catalyst for the methylene blue dye removal in aqueous matrices

This work developed efficient heterogeneous catalysts for the methylene blue (MB) dye degradation under photo-Fenton-like conditions. The material was modified to incorporate Fe(III) into ZnO, creating Fe/ZnO strucuture, and applied as heterogeneous catalysts at various pH levels. SEM analysis revealed an agglomerated and plate-like morphology of the synthesized catalysts. The enhanced structure facilitated a removal efficiency of 96.2% for MB dye when employing the photo-Fenton-based process using 5.0% Fe/ZnO catalyst. The high removal efficiency is attributed to the synergy between ≡Fe(III) and ≡Zn(II), which promotes the generation of photoradical species through the Fenton effect. Real water matrices served as a source of MB dye contamination, exhibiting minimal interference and achieving ∼100 % of removal. Scavenger studies indicate that •OH and e⁻ are the primary contributors to the high MB dye degradation efficiency. Additionally, the by-products formed after photo-Fenton process exhibit minimal toxicity towards Lactuca sativa L. No Fe(II) ions were leached at the end of the process. Eight cycles of degradation did not cause significant spectral changes in the FTIR analysis, as well as in the XRD patterns, indicating the material efficient and stable structure.

Novel and reusable magnetic MOF nanocomposite coupled ionic liquid- promoted efficient chemical fixation of CO2 into α-alkylidene cyclic carbonates

Carbon dioxide as a C1 building block to synthesize α-alkylidene cyclic carbonates is an environmental and sustainable approach. In this work, we designed and synthesized a type of multifunctional magnetic MOF nanocomposite catalysts, which could realize the carboxylic cyclization of CO2 and propargylic alcohols into α-alkylidene cyclic carbonates under solvent-free conditions. Among all the prepared nanocomposites, the MnFe2O4@SiO2@Cu-MOF nanocomposite is the best in catalytic activity combined with the tetrabutylphosphonium acetate ([Bu4P]OAc) ionic liquid cocatalyst. The catalytic system MnFe2O4@SiO2@Cu-MOF/[Bu4P]OAc displayed excellent performance in catalyzing the carboxylic cyclization of CO2 and different propargylic alcohols, and a series of α-alkylidene cyclic carbonates were obtained in high to excellent yields (88 ∼ 98 %) under mild reaction conditions (0.2 MPa, 35 °C). In addition, the two-component catalytic system had high stability and reusability, and can be easily separated and reused up to six consecutive cycles without considerable decrease in catalytic activity. Moreover, using the ionic liquid [Bu4P]OAc as the cocatalyst, the nanocomposite had good substrate adaptability for the catalytic carboxylic cyclization, which opens interesting prospects for the development of new magnetic MOF nanocomposites as efficient heterogeneous catalysts for the chemical transformation of CO2 into value-added chemicals.

Mesostructured Bifunctional ZnBr2/g‐C3N4 Catalysts Towards Efficient Cocatalyst‐Free Cycloaddition of CO2 to Propylene Carbonate

AbstractCatalytic cycloaddition of CO2 with propylene oxide (PO) is a sustainable pathway for the synthesis of propylene carbonate (PC), and the design of efficient heterogeneous catalysts is a hot research topic in both C1 chemistry and functional materials. In this work, graphitic carbon nitride (g‐C3N4) materials were prepared using urea (U) and melamine (M) as precursors through one‐step thermal condensation and then applied as catalyst supports for ZnBr2. As heterogeneous catalysts, the synthesized composites (ZnBr2/g‐C3N4‐MU) exhibited higher activity in the cycloaddition reaction of CO2 to PC than ZnBr2/g‐C3N4‐M and ZnBr2/g‐C3N4‐U. The preparation temperature of ZnBr2/g‐C3N4‐MU could affect the distributions of nitrogen species and acidic strength, which thus determined the final catalytic activity. More importantly, the loading of ZnBr2 not only introduced acidic sites but also enhanced the strength of alkaline sites of g‐C3N4‐MU, enabling ZnBr2/g‐C3N4‐MU materials as acid–base bifunctional catalysts in cycloaddition of CO2 with PO.

Acid and magnetic modifications of gum arabic as a dual approach for preparation of an efficient heterogeneous catalyst for conversion of fructose to value-added furanic compound

Acid and magnetic modifications of gum arabic as a dual approach for preparation of an efficient heterogeneous catalyst for conversion of fructose to value-added furanic compound

Green Synthesis of Magnetic Fe2O3 Nanoparticle with Chenopodium glaucum L. as Recyclable Heterogeneous Catalyst for One-Pot Reactions and Heavy Metal Adsorption.

The growth of the environment depends upon developing greener and ecological methods for managing pollutants and contamination from industrial wastewater, which causes significant effects on human health. The removal of these pollutants from wastewater using nanomaterials covers an ecological method that is free from expensive and secondary pollution. In this report, we developed magnetic iron nanoparticles from Chenopodium glaucum (CG), which showed excellent adsorption capacity at pH 5 for selective Hg2+ and Pb2+ metal ions among various heavy metal ions, with maximum adsorption capacities of 96.9 and 94.1%, respectively. These metals' adsorption process conforms to the Langmuir model, which suggests that monolayer adsorption transpires on CG-Fe2O3 nanoparticles. CG-Fe2O3 nanoparticles also act as an efficient and recyclable heterogeneous catalyst for one-pot synthesis of xanthene derivatives, yielding products with high yields (up to 97%) and excellent purity (crystalline form) within a short timeframe (6 min) using microwave irradiations (at 120 W).

Fabrication of heterogeneous catalyst for production of biodiesel form municipal sludge

Sewage sludge, a semi-solid byproducts of municipal wastewater treatment processes, offers a sustainable and cost-effective feedstock for biodiesel production through the synthesis of catalytic heterogeneous catalysts. In this study, we developed a novel heterogeneous catalyst by impregnating aluminum nitrate and calcite, obtained from carbon dioxide-sequestering bacteria, onto DigSBiochar (Biochar derived from digested sewage sludge). The produced catalyst was subsequently immobilized with the lipase enzyme isolated from Bacillus sp., creating a bioactive material for the transesterification of lipids in sewage sludge. Comprehensive characterization of the biocatalysts was conducted using Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FE-SEM). Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the resulting fatty acid methyl esters (FAMEs) demonstrated that the highest yield was achieved with the enzyme immobilized on the activated heterogeneous catalyst using methanol (99 %), followed by the activated heterogeneous catalyst with methanol (96 %), and methanol with Sulfuric acid (82 %). This study underscores the potential of utilizing municipal sewage sludge as a valuable resource for producing efficient heterogeneous catalysts, thereby advancing sustainable waste management practices and promoting renewable energy production.

Eco-Friendly Cellulose-Supported Nickel Complex as an Efficient and Recyclable Heterogeneous Catalyst for Suzuki Cross-Coupling Reaction.

In this work, we applied commercially available 2-pyridinecarboxylic acid to modify cellulose by simple manipulations, and then anchored low-toxicity metal nickel onto the modified cellulose to prepare the heterogeneous catalyst (CL-AcPy-Ni). The obtained catalyst was characterized by FT-IR, TG-DSC, BET, XRD, SEM-EDS, ICP-OES, XPS, and GPC. The catalytic performance of CL-AcPy-Ni in the Suzuki cross-coupling reaction was investigated using 4-methyl iodobenzene and phenylboronic acid as the model substrates reacting in THF under 120 °C for 24 h. The catalytic ability of CL-AcPy-Ni for various halobenzenes and phenylboronic acid derivatives was also further investigated under optimal conditions and demonstrated good catalytic activity, and a series of diaryls were successfully synthesized. Finally, this green nickel-based catalyst could be reused for five successive cycles by simple centrifugation.

Recovering noble metals from waste streams using porous organic frameworks for heterogeneous catalysis

AbstractRecovering noble metals from waste resources and incorporating them into catalysts stands out as a promising strategy for advancing sustainability within the catalysis field. This review provides a comprehensive overview of recent investigations into noble metal recovery from waste streams, specifically employing porous organic frameworks (POFs). Additionally, the study delves into the utilization of the resultant composites, enriched with noble metals, in heterogeneous catalysis. Moreover, we offer insights into the challenges faced and outline prospects for the practical implementation of extracting noble metal catalysts from waste streams using POFs, aiming to develop cost-effective, sustainable, and efficient heterogeneous catalysts.