Recyclable Catalyst Research Articles

Synthesis of Biheteroaryls by Pd-Catalyzed Homocoupling of Heteroaryl Bromides.

Symmetrical biheteroaryl compounds, such as bypyridines and bipyrazoles, are important ligands in transition-metal catalysis. They also serve as synthetic precursors of photo catalysts/sensitizers, bioactive agents, and energetic materials. To facilitate the concise synthesis of these useful structures, an efficient Pd-catalyzed homocoupling of heteroaryl bromides has been successfully established using the electron-rich and sterically hindered monophosphorus ligand BIDIME. The coupling protocol features a tandem Miyaura borylation/Suzuki coupling sequence and exhibits unprecedented tolerance of a wide range of heteroaryl bromides, providing a series of symmetrical biheteroaryls in moderate to good yields. Notably, the use of the corresponding polymeric ligand, PolyBIDIME, enabled the recycling of a palladium catalyst, demonstrating the potential of the homocoupling in practical applications.

Palladium-Functionalized Polysiloxane Drop-Casted on Carbon Paper as a Heterogeneous Catalyst for the Suzuki-Miyaura Reaction.

In this work, a Pd(II)-C,N-cyclometalated complex was grafted to polysiloxanes via azide-alkyne cycloaddition. The obtained polymer-metal complex (Pd-PDMS) acts as a catalyst in the Suzuki-Miyaura reaction. Pd-PDMS was drop-casted onto a carbon fiber support, and the resulting membrane demonstrated catalytic activity in the cross-coupling reaction without yield loss after several catalytic cycles. The catalytic membrane allows for easy catalyst recycling and provides ultra-low palladium levels in Suzuki-Miyaura reaction products.

Catalytically Active Site Mapping Realized through Energy Transfer Modeling.

The demands of a sustainable chemical industry are a driving force for the development of heterogeneous catalytic platforms exhibiting facile catalyst recovery, recycling, and resilience to diverse reaction conditions. Homogeneous-to-heterogeneous catalyst transitions can be realized through the integration of efficient homogeneous catalysts within porous matrices. Herein, we offer a versatile approach to understanding how guest distribution and evolution impact the catalytic performance of heterogeneous host-guest catalytic platforms by implementing the resonance energy transfer (RET) concept using fluorescent model systems mimicking the steric constraints of targeted catalysts. Using the RET-based methodology, we mapped condition-dependent guest (re)distribution within a porous support on the example of modular matrices such as metal-organic frameworks (MOFs). Furthermore, we correlate RET results performed on the model systems with the catalytic performance of two MOF-encapsulated catalysts used to promote CO2 hydrogenation and ring-closing metathesis. Guests are incorporated using aperture-opening encapsulation, and catalyst redistribution is not observed under practical reaction conditions, showcasing a pathway to advance catalyst recyclability in the case of host-guest platforms. These studies represent the first generalizable approach for mapping the guest distribution in heterogeneous host-guest catalytic systems, providing a foundation for predicting and tailoring the performance of catalysts integrated into various porous supports.

Emerging ZnO Semiconductors for Photocatalytic CO2 Reduction to Methanol.

Carbon recycling is poised to emerge as a prominent trend for mitigating severe climate change and meeting the rising demand for energy. Converting carbon dioxide (CO2) into green energy and valuable feedstocks through photocatalytic CO2 reduction (PCCR) offers a promising solution to global warming and energy needs. Among all semiconductors, zinc oxide (ZnO) has garnered considerable interest due to its ecofriendly nature, biocompatibility, abundance, exceptional semiconducting and optical properties, cost-effectiveness, easy synthesis, and durability. This review thoroughly discusses recent advances in mechanistic insights, fundamental principles, experimental parameters, and modulation of ZnO catalysts for direct PCCR to C1 products (methanol). Various ZnO modification techniques are explored, including atomic size regulation, synthesis strategies, morphology manipulation, doping with cocatalysts, defect engineering, incorporation of plasmonic metals, and single atom modulation to boost its photocatalytic performance. Additionally, the review highlights the importance of photoreactor design, reactor types, geometries, operating modes, and phases. Future research endeavors should prioritize the development of cost-effective catalyst immobilization methods for solid-liquid separation and catalyst recycling, while emphasizing the use of abundant and non-toxic materials to ensure environmental sustainability and economic viability. Finally, the review outlines key challenges and proposes novel directions for further enhancing ZnO-based photocatalytic CO2 conversion processes.

An efficient and green synthesis of dihydrothiazolo [3,2-a] purine-2 (1H)-one derivatives using bleaching earth clay (BEC) as a recyclable catalyst and study of antibacterial potency

An efficient and green synthesis of dihydrothiazolo [3,2-a] purine-2 (1H)-one derivatives using bleaching earth clay (BEC) as a recyclable catalyst and study of antibacterial potency

Construction of magnetic Fe2O3-Decorated electroactive Poly(amic acid) composites as recyclable Catalysts: Increased loading of gold Nanoparticles, Controlled Size, and Accelerated catalytic reduction of 4-Nitrophenol

Nanocomposites are widely used in heterogeneous catalysts in the field of water treatment, which exhibit controllable structural advantages and synergistic effects between their components further enhancing catalytic activity. In the current research, we developed the Au nanoparticles immobilized magnetic γ-Fe2O3/Electroactive Poly (amic acid) composite (6Au/EPAA-Fe2O3) prepared by using the in-situ redox reaction strategy. Sundry techniques such as FT-IR, XRD, TGA, SEM/HR-TEM, CV, and XPS analysis have been applied to explain the chemical structure and morphology of as-synthesized composites. The catalytic performance of the catalyst during the reduction of 4-nitrophenol using NaBH4 as a hydrogen donor was assessed in an aqueous medium at room temperature. Attractively, 6Au/EPAA-Fe2O3 composite exhibits superior catalytic performance, which completes the reduction of 4-NP within the 50 s. The pseudo-first-order kinetic rate constants were estimated as 3.0 × 10-2 s−1 for the reduction of 4-NP. Furthermore, the 6Au/EPAA-Fe2O3 composite has excellent stability and reproducibility of 10 consecutive runs by using an external magnet without loss of catalytic activity.

Synthesis and application of merrifield resin based supported ionic liquids as organocatalyst for the greener synthesis of bio-active triazoles

A green and highly efficient catalysts based on merrifield resin supported acidic ionic liquids (MRBT-SILs) were synthesized using merrifield resin (non-toxic and chemically inert) and benzothiazole. The application of MRBT-SILs for the greener synthesis of 1,2,4-triazole-3-thiones or 1,2,4-triazole-3-oxones from condensation of ketones and thiosemicarbazide or semicarbazide respectively in 60% ethanol under ultra-sonication was studied. The protocol so developed has many additional benefits compared to those reported in previous articles such as smooth reaction, use of alcohol as solvent, good yield, ambient temperature, an easy workup procedure, catalyst recyclability, and high atom economy, making it highly efficient for synthesis as it obeys green chemistry principles. Further, catalyst could be reused up to eight cycles without any loss of its catalytic activity.

Post-functionalized cellulose/metal-organic framework composite with sulfonic acid: An efficient, rapid and recyclable bio-based solid acid catalyst for the synthesis of 5-hydroxymethylfurfural.

A new acid catalyst derived from renewable sources was developed using an ultrasound-assisted approach. This involved the formation of a metal-organic framework called MIL-88(Fe) in the presence of carboxymethylated-cellulose (CMC). Subsequently, the catalyst underwent a post-synthetic modification to introduce further acidic -SO3H groups into the structure of the CMC/MIL-88(Fe) composite. Various examinations were carried out that validated the successful creation of the CMC/MIL-88(Fe)-SO3H catalyst. The effectiveness of the catalyst was assessed in the process of solid acid catalysis, specifically in the dehydration of fructose to produce 5-hydroxymethylfurfural (HMF). Through the employment of Response Surface Method (RSM) optimization, it was determined that utilizing 34wt% of the catalyst at a temperature of 90°C for 30min resulted in a remarkable 98% HMF yield. The catalyst exhibited good reusability, as it retained its catalytic effectiveness throughout four consecutive cycles. Comparative catalytic investigations involving CMC and CMC/MIL-88(Fe) composite without sulfonation revealed the superior activity of CMC/MIL-88(Fe)-SO3H catalyst, emphasizing the collaborative effect of CMC, MIL-88(Fe), and the impact of post-functionalization with -SO3H on the performance of the catalyst.

Nanostructured NiCo2S4 immobilized on nickel foam as recyclable catalyst for activating peroxymonosulfate toward doxycycline degradation: Performance and mechanism

The existing powder catalysts used in sulfate radical-based advanced oxidation processes (SR-AOPs) commonly suffer from severe limitation due to the difficulty of recycling and inadequate exposure of the active site. In this work, spinel sulfide (NiCo2S4) was uniformly grown on 3D nickel foam (NF) through a one-step hydrothermal route for the activation of peroxymonosulfate (PMS) toward highly efficient degradation of doxycycline (DOX). Due to the synergistic effect of Ni and Co in the NiCo2S4, the NiCo2S4/NF (0.6 g/L) combined with PMS (3.0 mmol L-1) can promote a nearly complete degradation (98.2 %) toward 0.3 mmol/L DOX within 6 min. Density functional theory (DFT) calculations illustrated that the NiCo2S4/NF can adsorb PMS through a unique Ni-S-Co structure and “conducting bridge” mode of NF, accelerating the electron transfer from NiCo2S4/NF to PMS and the subsequent O-O bond cleavage. Especially, the Co/Ni dual-site enhanced the adsorption of PMS and promotes electron transfer to form surface-activated PMS complex (catalyst-PMS*), leading to the generation of surface-bound reactive oxygen species (ROS) on the NiCo2S4 surface. Quenching experiments and ESR tests demonstrated that radicals such as SO4•-, 1O2, •OH and surface-bound ROS play a vital role in DOX degradation. Moreover, the potential mechanism and pathway of DOX degradation are reasonably deduced by investigating and analyzing the intermediates with liquid chromatography-mass spectromsetry (LC-MS). Consequently, this study provides a deep insight on the systhsis of spinel sulfide and its intrinsic mechanism of PMS activation toward organic contaminant degradation.

One‐Pot Multicomponent Synthesis of Substituted 1,6‐Naphthyridine Derivatives Employing 4‐Aminocumarin

ABSTRACTThis study synthesized 1,6‐naphthyridine as a novel class of fused heterocyclic compounds with high efficiency using a multicomponent reaction. The reaction involved benzaldehyde or its derivatives, 2 mol of malononitrile, and 4‐aminocumarin in an aqueous solution at room temperature in the presence of SiO2/Fe3O4@MWCNTs as a recyclable catalyst. This study examines the antioxidant properties of 1,6‐naphthyridine in addition to the other research undertaken in this work. The production process of 1,6‐naphthyridine demonstrated several advantageous features, including rapid reactions, high yields of the final product, and straightforward separation of the catalyst and product from the reaction mixture.

“Guanidine hydrochloride assisted one-pot synthesis of 2-amino-4,6-disubstituted-3-cyanopyridine derivatives: a sustainable and greener strategy with catalyst recyclability”

“Guanidine hydrochloride assisted one-pot synthesis of 2-amino-4,6-disubstituted-3-cyanopyridine derivatives: a sustainable and greener strategy with catalyst recyclability”

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).

Direct construction of imidazoles via oxidative C(sp3)–H amination and annulation of aryethylamines by a Single-Atom cobalt catalyst

The development of reusable catalytic systems for achieving site-selective functionalization of C(sp3)-H bond remains a significant challenge. Herein, we designed a modified metal–organic framework (MOF)-derived N, P co-doped carbon supported single-atom cobalt catalyst, which was successfully applied in oxidative C(sp3)–H amination and cyclization of aryethylamines for construction of polysubstituted imidazoles. The advantages of the present method include: broad substrate scope, recyclable base metal catalyst, and naturally abundant O2 as green oxidant. The structural − activity relationship of the catalyst indicated that the atomically dispersed CoN3P1 is the active species responsible for the catalytic process. Furthermore, the synthesized imidazoles exhibited exceptional insecticidal activity against wheat pests, and may become lead molecules in the development of novel agricultural pesticide candidates, with significant application potential.

Layered silicate PLS-3 with PREFER structure supported Pd nanoparticles: A recyclable catalyst for the synthesis of furfuryl ethyl ether

Supported Pd catalysts has found wide applications in reductive etherification of aldehydes. However, the synthesis of furfural-derived ethers on Pd catalysts has encountered great challenges because several side reactions such as over-hydrogenation of furan ring and decarbonylation always occur simultaneously under the reaction conditions. We herein reported the catalytic performance of Pd nanoparticles (∼4 nm) supported on the external surface of layered structured PLS-3 zeolite with narrow pore size (<0.4 nm) and large external surface area (80–100 m2/g). The PLS-3 with Si/Al of 92 having total acid sites of 93 μmol/g showed satisfied ether selectivity. Pd nanoparticles located on the external surface showed better etherification selectivity than those confined in the framework, due to the less diffusion limitation of furfural acetal as an intermediate.

Chiral Polymeric Diamine Ligands for Iridium-Catalyzed Asymmetric Transfer Hydrogenation.

A series of polymeric chiral diamine ligands are developed by diboron-templated asymmetric reductive couplings, and their iridium complexes Ir-polydiamines are efficient and recyclable catalysts for asymmetric transfer hydrogenation (ATH) of functionalized ketones, affording a series of optically active secondary alcohols in excellent enantioselectivities (up to 99% ee) and unprecedentedly high total TONs (12,000, six cycles). Ir-polydiamine catalysts with longer chains offered higher reactivities, providing a plausible deactivation mechanism and practical solutions of ATH for vitamin B5 and phenylephrine.

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.

Highlighting multicomponent reactions as an efficient and facile alternative route in the chemical synthesis of organic-based molecules: a tremendous growth in the past 5 years.

Since Strecker's discovery of multicomponent reactions (MCRs) in 1850, the strategy of applying an MCR approach has been in use for over a century. Due to their ability to quickly develop molecular diversity and structural complexity of interest, MCRs are considered an efficient approach in organic synthesis. Although MCRs such as the Ugi, Passerini, Biginelli, and Hantzsch reactions are widely studied, this review emphasizes the significance of selective MCRs to elegantly produce organic compounds of potential use in medicinal chemistry and industrial and material science applications, as well as the use of the MCR approach to sustainable methods. During synthesis, MCRs provide advantages such as atom economy, recyclable catalysts, moderate conditions, preventing waste, and avoiding solvent use. MCRs also reduce the number of sequential multiple reactions to one step.

Pd-imidate@SBA-15: a multifunctional heterogeneous catalyst for the aqueous room temperature hydrogenation of CO2 to formic acid.

The incorporation of hydrophilic and basic sites from phosphotriazaadamantane and saccharine in a water-soluble Pd complex and the subsequent confinement into mesoporous silica support increases the activity and stability of the palladium catalytic species for the room-temperature aqueous hydrogenation of either bicarbonate or CO2 into formic acid. The use of low Pd loadings (<0.1mmolPd·g-1) of the well-dispersed complex on SBA-15 mesoporous silica allows performing the reaction under room temperature, and aqueous conditions, exhibiting TON of ca. 40-100, for the CO2 or bicarbonate hydrogenation, respectively, which is one order of magnitude higher than the homogeneous case, allowing the easy isolation and recycling of the solid catalyst.

Cost-efficient electrosynthesis of hydrogen peroxide in acidic and neutral solutions

Oxygen reduction reaction is considered a green and low-carbon approach for H2O2 production. Low space-time yield and high energy consumption are serious challenges to the implementation of a commercial scale now. A cost-efficient H2O2 electrosynthesis using a recycled gold catalyst is developed here. The carbon-supported gold catalyst is synthesized using electroplating gold wastewater, which indicates good catalysis performances for both sulfite oxidation and H2O2 production. The sulfite/air fuel cell adopting the bifunctional gold catalyst can directly produce 8.70±0.53 g L−1 H2O2 in 0.5 mol L−1 Na2SO4 solution, with a good current efficiency of 71.56 %±2.13 % and a remarkable space-time yield of 27.20±1.17 mg cm−2 h−1. Adopting the desulfurization solution from flue gas as the anodic sacrificial agent, the electricity costs for acidic and neutral H2O2 electrosynthesis are only 2.09–3.82 kWh kg−1. The reported H2O2 electrosynthesis performances, especially for power consumption, are also summarized and compared.

Construction of Co(II), Cu(II), and Zn(II) coordination compounds driven by a pyridine-dicarboxylic acid: Hydrothermal assembly, structural and topological versatility, and catalytic properties

A derivative of pyridine-dicarboxylic acid, 5-(3-carboxyphenyl)picolinic acid (H2cpic), was used as a versatile building block to synthesize a series of five novel coordination compounds under hydrothermal conditions and formulated as {[Cu2(μ-cpic)2(phen)]·H2O}n (1), [Co(μ-cpic)(phen)(H2O)]n (2), [Cu2(μ-cpic)2(2,2′-bipy)(H2O)2]·2H2O (3), {[Cu3(μ-cpic)3(μ-4,4′-bipy)1.5(H2O)3]·2H2O}n (4), and {[Zn2(μ-cpic)2(μ-dpe)0.5(H2O)3]·H2O}n (5). The auxiliary ligands used in the synthesis were 1,10-phenanthroline (phen), 2,2′-bipyridine (2,2′-bipy), 4,4′-bipyridine (4,4′-bipy), and 1,2-di(4-pyridyl)ethylene (dpe). The structures of the compounds 1–5 vary significantly, ranging from a 0D tetramer (3) to 1D metal–organic chains (1, 2, 4, and 5). Furthermore, these compounds were evaluated as heterogeneous catalysts for the Henry reaction, achieving high product yields under optimized conditions. We further investigated various reaction parameters, and substrate scope, and assessed the feasibility of catalyst recycling. This thorough investigation highlights the versatility of H2cpic as a dicarboxylate building block in the formation of functional coordination polymers.