Tandem Process Research Articles

Covalent Phenanthroline‐Porphyrin Polymer for Aminocarbonylation through Electro/Thermocatalytic Tandem Processes: Extending Chemical Valorization of CO2

AbstractThe covalent organic frameworks/polymers configurated with metal‐N4 conjugated structures offer an exceptional platform for efficient electrochemical CO2 reduction reaction (eCO2RR). However, understanding the impact of the structure‐mediated local microenvironment and integrating CO2 electroreduction with follow‐up utilization toward extending chemical valorization of CO2 are still far from sufficient. Herein, a set of covalent phenanthroline‐porphyrin polymers are designed to decode the microenvironment modulation originating from built‐in structures, and the optimized one delivered an extraordinary performance for eCO2RR with ≈100% Faradaic efficiency of CO under stabilized CO2‐electrolysis of 70 h. The experimental and theoretical analyses suggest that the regulation of the Co‐N4 electronic structures and microenvironment convoys the stabilized formation of key reaction intermediate *COOH. Furthermore, through CO‐mediated electro/thermocatalytic tandem processes, the aminocarbonylation of aryl iodides and amines with high yields has been convincingly implemented over the coordinated Pd sites, which is remarkably helpful to propel extending chemical valorization of CO2.

A Hierarchical Metal-Organic Framework Composite Aerogel Catalyst Containing Integrated Acid, Base, and Metal Sites for the One-Pot Catalytic Synthesis of Cyclic Carbonates.

Catalysis has played a decisive role in the development of unique chemical reactions to produce important chemicals. However, conventional stepwise synthetic routes that rely on individual catalysts to promote each step often suffer from ponderous processes for the isolation of intermediates that result in massive material losses and large economic expenditures. In addition, traditional powder forms of these catalysts suffer from poor processability and recoverability. Herein, we designed and prepared a hierarchical metal-organic framework (MOF) composite monolithic catalyst IL-Au@UiO-66-NH2/CMC that contains integrated acid (Zr4+), base (ionic liquid (IL)), and metal sites (Au nanoparticles (NPs)) to promote the one-pot preparation of cyclic carbonates from styrene derivatives and CO2. Highly dispersed Au NPs, IL 1-aminoethyl-3-methylimidazolium bromide ([C2NH2 MIM] [Br]), and MOF-positioned Lewis acid sites within this composite aerogel are separately responsible for catalyzing selective epoxidation of the styrene derivatives and the subsequent cycloaddition reaction of CO2 with intermediate styrene oxides. Importantly, inclusion of the imidazolium-based IL effectively modulates the size and chemical microenvironment of the Au NPs via electrostatic protection, leading to catalyst stability and its selective oxidation of styrene. Benefiting from the rapid mass transfer and high exposure of active sites within the pore-rich hierarchical nanostructure, IL-Au@UiO-66-NH2/CMC promotes high conversion (90.5%) of the styrene and selectivity (80.5%) for styrene carbonate (SC) formation in the one-pot process, a performance level that far exceeds those of related catalysts containing only Au NPs or IL (the selectivity of SC < 42%). Furthermore, the composite aerogel catalyst can be readily separated and recycled at least five times without a remarkable loss of activity and selectivity. The controllable integration of various active components in the hierarchical MOF composite aerogel herein should serve as the foundation for the design of multifunctional monolithic catalysts for other valuable tandem processes.

Tandem Hock and Friedel-Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold.

The Hock cleavage, which is compatible with tandem processes, was applied to the synthesis of 1-aryltetralines through a one-pot transformation from readily available benzyl(prenyl)malonate substrates. After the photooxygenation of the prenyl moiety, the resulting hydroperoxide was directly engaged in a Hock cleavage by adding a Lewis acid. The presence of an aromatic nucleophile in the reaction mixture and that of a benzyl moiety on the substrate resulted in tandem Friedel-Crafts reactions to form the 1-aryltetraline products. These compounds share a close analogy to the cyclolignan natural products. Experimental observations and a DFT study support the involvement of an aldehyde intermediate during the Friedel-Crafts reactions, rather than an oxocarbenium.

Tandem Nitrate-to-Ammonia Conversion on Atomically Precise Silver Nanocluster/MXene Electrocatalyst.

Electrocatalytic reduction of nitrate (NO3 RR) to synthesize ammonia (NH3 ) provides a competitive manner for carbon neutrality and decentralized NH3 synthesis. Atomically precise nanoclusters, as an advantageous platform for investigating the NO3 RR mechanisms and actual active sites, remain largely underexplored due to the poor stability. Herein, we report a (NH4 )9 [Ag9 (mba)9 ] nanoclusters (Ag9 NCs) loaded on Ti3 C2 MXene (Ag9 /MXene) for highly efficient NO3 RR performance towards ambient NH3 synthesis with improved stability in neutral medium. The composite structure of MXene and Ag9 NCs enables a tandem catalysis process for nitrate reduction, significantly increasing the selectivity and FE of NH3 . Besides, compared with individual Ag9 NCs, Ag9 /MXene has better stability with the current density performed no decay after 108 hours of reaction. This work provides a strategy for improving the catalytic activity and stability of atomically precise metal NCs, expanding the mechanism research and application of metal NCs.

Tandem Nitrate‐to‐Ammonia Conversion on Atomically Precise Silver Nanocluster/MXene Electrocatalyst

AbstractElectrocatalytic reduction of nitrate (NO3RR) to synthesize ammonia (NH3) provides a competitive manner for carbon neutrality and decentralized NH3 synthesis. Atomically precise nanoclusters, as an advantageous platform for investigating the NO3RR mechanisms and actual active sites, remain largely underexplored due to the poor stability. Herein, we report a (NH4)9[Ag9(mba)9] nanoclusters (Ag9 NCs) loaded on Ti3C2 MXene (Ag9/MXene) for highly efficient NO3RR performance towards ambient NH3 synthesis with improved stability in neutral medium. The composite structure of MXene and Ag9 NCs enables a tandem catalysis process for nitrate reduction, significantly increasing the selectivity and FE of NH3. Besides, compared with individual Ag9 NCs, Ag9/MXene has better stability with the current density performed no decay after 108 hours of reaction. This work provides a strategy for improving the catalytic activity and stability of atomically precise metal NCs, expanding the mechanism research and application of metal NCs.

Deep Cracking of Bulky Hydrocarbons into Light Products via Tandem Catalysis over Uniform Interconnected ZSM-5@AlSBA-15 Composites.

Deep cracking of bulky hydrocarbons on zeolite-containing catalysts into light products with high activity, desired selectivity, and long-term stability is demanded but challenging. Herein, the efficient deep cracking of 1,3,5-triisopropylbenzene (TIPB) on intimate ZSM-5@AlSBA-15 composites via tandem catalysis is demonstrated. The rapid aerosol-confined assembly enables the synthesis of the composites composed of a continuous AlSBA-15 matrix decorated with isolated ZSM-5 nanoparticles. The two components at various ZSM-5/AlSBA-15 mass ratios are uniformly mixed with chemically bonded pore walls, interconnected pores, and eliminated external surfaces of nanosized ZSM-5. The typical composite with a ZSM-5/AlSBA-15 mass ratio of 0.25 shows superior performance in TIPB cracking with outstanding activity (≈100% conversion) and deep cracking selectivity (mass of propylene + benzene > 60%) maintained for a long time (> 6h) under a high TIPB flux (2mLh-1), far better (several to tens of times higher) than the single-component and physically mixed catalysts and superior to literature results. The high performance is attributed to the cooperative tandem catalytic process, that is, selective and timely pre-cracking of TIPB to isopropylbenzene (IPB) in AlSBA-15 and subsequently timely diffusion and deep cracking of IPB in nanosized ZSM-5.

Synergistic catalytic conversion of nitrate into ammonia on copper phthalocyanine and FeNC two-component catalyst

Cu-based catalysts have been extensively studied to enhance the performance of the electrochemical nitrate reduction reaction (NO3–RR), while it is still a challenge to balance high ammonia (NH3) current density and Faradaic efficiency. Here, we incorporated nitrogen coordinated iron single atom catalyst (FeNC) with copper phthalocyanine (CuPc), denoted as CuPc/FeNC, for NO3–RR. Compared with the two individual catalysts, this two-component catalyst increases NH3 Faradaic efficiency and current density at low overpotentials, achieves efficient synergistic catalytic conversion. Experiments and theoretical calculations reveal that the enhanced electrochemical performance of CuPc/FeNC catalyst comes from the tandem process, in which NO2– is produced on CuPc and then transferred to FeNC and further reduced to NH3. In this exceptional tandem catalyst system, an outstanding NH3 Faradaic efficiency close to 100% was achieved at potentials greater than –0.35 V vs. RHE, coupled with a peak NH3 partial current density of 273 mA cm–2 at –0.57 V vs. RHE, effectively suppressing NO2– production across the entire potential range. This strategy provides a design platform for the continued advancement of NO3–RR catalysts.

Demethylenative cyclization of 1,7-enynes using α-amino radicals as a traceless initiator enabled by Cu(I)-photosensitizers.

A rare type of demethylenative intramolecular cyclization of 1,7-enynes to access quinoline-2-(1H)-ones has been successfully developed under the catalysis of P/N-heteroleptic Cu(I)-photosensitizers. Preliminary mechanistic experiments revealed that the key to the success of this protocol lay in the α-amino radical addition-triggered tandem process of intramolecular radical cyclization/1,5-HAT/β-fragmentation. This protocol provides a new avenue for the deconstructive cyclization of alkene derivatives.

A formal (3 + 2) annulation–Cannizzaro cascade of bifunctional peroxides for the synthesis of dihydrofurans

Tunable tandem processes of bifunctional peroxides allow the divergent construction of functionalized dihydrofurans and epoxides by simply changing the basic conditions.

Visible-light-induced self-catalyzed fluoroalkylation/cyclization of N-arylcinnamamides: synthesis of fluoroalkyl-containing 3,4-disubstituted dihydro-1,5-naphthyridin-2(1H)-ones and 7,8-disubstituted dihydropyrido[3,2-d]pyrimidin-6(5H)-ones

A novel visible-light-mediated fluoroalkylation/cyclization tandem process for constructing fluoroalkyl-containing 3,4-disubstituted dihydro-1,5-naphthyridin-2(1H)-ones and 7,8-disubstituted dihydropyrido[3,2-d]pyrimidin-6(5H)-ones has been explored.

Nickel-catalyzed regiodivergent sulfonylarylation of 1,3-enynes to access allenes and dienes.

The radical-mediated difunctionalization of 1,3-enynes facilitates rapid access to structurally diverse allenes and dienes. Whereas, owing to the existence of multiple active sites in conjugated 1,3-enynes, regulating selectivity in difunctionalized addition via a single transition-metal-catalyzed radical tandem process remains elusive. Herein, we disclose an intriguing protocol of substrate-controlled nickel-catalyzed regiodivergent sulfonylarylation of 1,3-enynes with the assistance of sulfonyl chlorides and arylboronic acids. This valuable synthetic utility respectively delivers a series of highly functionalized and synthetically challenging allenyl sulfones and dienyl sulfones from fine-tuned 1,3-enynes by one step, which provides a facile approach for complex sulfone-containing drug molecules synthesis.

Modular synthesis of pyrrole-fused heterocycles via glucose-mediated nitro-reductive cyclization.

A novel biomass-derived glucose-mediated one-pot multicomponent nitro-reductive cyclization method is presented for the direct synthesis of diverse pyrrole-fused heterocycles. The process involves two-component reactions of alkyl (NH)-pyrrole-2-carboxylates and 2-fluoronitroarenes, yielding pyrrolo[1,2-a]quinoxalin-4(5H)-ones, as well as three-component reactions utilizing (NH)-pyrroles, nitroarenes, and DMSO as carbon sources, resulting in various pyrrolo[1,2-a]quinoxaline derivatives. High yields were achieved with broad substrate scope and gram-scale synthesis capability, including pharmaceuticals featuring pyrroloquinoxaline scaffolds. The method's key innovation lies in enabling three or four reactions in a single-pot setup, previously unexplored in pyrrole chemistry. The simplicity of nitro group reduction by biomass-derived glucose ensures practical safety during scale-up, while mechanistic insights from control experiments reveal a new paradigm in pyrrole chemistry. The tandem process demonstrates low PMI values and high step and atom economies, aligning well with green chemistry principles.

Tek Proseste Kompaund Elde Edebilen Tandem Bir Sistemle Yapılan Termoplastik Geri Dönüşümünün Çevreye ve Dünyaya Faydaları

The manufacture of polymers has experienced significant growth since the 1900s due to their favorable attributes such as ease of manufacturing, cost-effectiveness, desirable chemical and physical qualities, as well as their lightweight nature. The escalating utilization of plastic has begun to inflict damage upon the environment, organisms, and human well-being, hence giving rise to challenges pertaining to recycling and waste management. In the process of recycling, it is necessary to subject thermoplastics to two cycles of melting in order to get the correct material characteristics. As a result of the restricted number of mechanical recycling cycles for plastics, thermoplastics have an accelerated rate of expiration, double the usual timeframe. In the proposed tandem recycling process, a single melting operation can subject the trash that has already undergone recycling to a second round of recycling. By using this approach, the potential for enhancing the reusability of thermoplastic waste is heightened. The absence of an additional heating process results in energy savings, leading to a notable reduction in expenses.

Aynı Yöne Dönen Çift Vidalı Ekstrüderli Tandem Bir Termoplastik Geri Dönüşüm Sisteminde Vida Yapılanmasının İncelenmesi

Polymers have rapidly replaced the utilization of glasses, ceramics, metals, and organic textiles due to their cost-effectiveness, lightweight nature, and enhanced functionality. Nevertheless, as a consequence of their chemical composition, polymers undergo a protracted degradation process in natural environments, resulting in a significant accumulation of plastic waste since their inception. This accumulation has now reached a critical threshold, posing a substantial risk to both human well-being and the preservation of natural ecosystems. In the recycling process of thermoplastic wastes, it is necessary to subject them to two rounds of melting in order to obtain compounds. This practice results in a reduction of the recycling numbers associated with thermoplastics, which possess a finite recycling lifespan, by 50%. The present work involved the construction of a tandem recycling process, wherein molten waste polymers were immediately introduced into a co-rotating twin screw extruder. In contrast to alternative approaches, a process-dependent screw configuration has been devised for the twin-screw system employed in the delivery of molten material. The product derived from 80% waste thermoplastic was thereafter compared to the original product as an outcome of the aforementioned procedure. Properties similar to those of pure Polypropylene were seen in some physical and chemical characteristics.

Photocatalytic Production of Ethanolamines and Ethylenediamines from Bio‐Polyols over a Cu/TiO2 Catalyst

AbstractValorization of biomass‐derived polyols into high‐value‐added ethanolamines and ethylenediamines is highly attractive. Herein, we report a one‐step photocatalytic protocol to convert bio‐polyols into a 60 % yield of ethanolamines and ethylenediamines over a multifunctional Cu/TiO2 catalyst. This catalyst enables a tandem process of photocatalytic polyol C−C bond cleavage and reductive amination in one pot at room temperature, and also allows the selective conversion of various bio‐polyols and amines. Mechanistic studies revealed that photogenerated holes in TiO2 promote the retro‐aldol C−C bond cleavage or oxidative dehydrogenation of polyols, and photogenerated electrons accumulate on small‐sized Cu clusters, which facilitate the reductive amination via hydrogen transfer and prevent the H2 generation. This strategy provides new opportunities for the development of non‐noble metal photocatalysts and methods of biomass conversion under mild conditions.

Tandem aqueous extract of onion catalyzed Knoevenagel condensation-Michael addition-cyclization: A green synthesis of 2-amino- 3-cyano-4H-pyran derivatives and their anti-oxidant and molecular docking studies

Aqueous extract of onion catalyzed tandem process incorporating Knoevenagel condensation followed by Michael addition-cyclization is revealed using aldehyde 1, malononitrile 2a and an active methylene compound 3. This method caused diverse 2-amino- 3-cyano-4H-pyran annulated heterocyclic scaffolds in excellent yields (up to 98 %). The synthesized compounds 4ah were also analyzed by single-crystal X-ray diffraction. The reactivity of the active methylene compounds and reasonable mechanism for sequential tandem reactions have been described. Also, this methodology has a simple, easy workup, short reaction time, without column chromatography and eco-friendly reaction conditions. Seventeen out of forty-five synthesized pyran derivatives were screened for their in vitro antioxidant studies. Among the compounds 4ai, 4aj, 4al, 4cd, 4ca, 4cb, 4cc, 4cd have shown excellent and 4aa, 4ac, 4ae, 4ah have exhibited comparable antioxidant activity with ascorbic acid standard. Compounds 4ch-4ck exhibited excellent antioxidant activity than standard. Moreover, mushroom tyrosinase (mh-Tyr) has performed molecular docking properties.

Photocatalytic Production of Ethanolamines and Ethylenediamines from Bio-Polyols over a Cu/TiO2 Catalyst.

Valorization of biomass-derived polyols into high-value-added ethanolamines and ethylenediamines is highly attractive. Herein, we report a one-step photocatalytic protocol to convert bio-polyols into a 60 % yield of ethanolamines and ethylenediamines over a multifunctional Cu/TiO2 catalyst. This catalyst enables a tandem process of photocatalytic polyol C-C bond cleavage and reductive amination in one pot at room temperature, and also allows the selective conversion of various bio-polyols and amines. Mechanistic studies revealed that photogenerated holes in TiO2 promote the retro-aldol C-C bond cleavage or oxidative dehydrogenation of polyols, and photogenerated electrons accumulate on small-sized Cu clusters, which facilitate the reductive amination via hydrogen transfer and prevent the H2 generation. This strategy provides new opportunities for the development of non-noble metal photocatalysts and methods of biomass conversion under mild conditions.

Unconventional Synthesis of Hierarchically Twinned Copper as Efficient Electrocatalyst for Nitrate-Ammonia Conversion.

Twin boundary (TB) engineering provides exciting opportunities to tune the performance levels of metal-based electrocatalysts. However, the controllable construction of TB greatly relies on surfactants, blocking active sites, and electron transfer by surfactants. Here, a surfactant-free and facile strategy is proposed for synthesizing copper (Cu) nanocatalysts with dense hierarchical TB networks (HTBs) by the rapid thermal reductions in metastable CuO nanosheets in H2 . As revealed by in situ transmission electron microscopy, the formation of HTBs is associated with the fragmentation of nanosheets in different directions to generate abundant crystal nuclei and subsequently unconventional crystal growth through the collision and coalescence of nuclei. Impressively, the HTBs endow Cu with excellent electrocatalytic performance for direct nitrate-ammonia conversion, superior to that of Cu with a single-oriented TB and without TB. It is discovered that the HTBs induce the formation of compressive strains, thereby creating a synergistic effect of TBs and strains to efficiently tune the binding energies of Cu with nitrogen intermediates (i.e., NO2 *) and thus promote the tandem reaction process of NO3 - -to-NO2 - and subsequent NO2 - -to-NH3 electrocatalysis. This work demonstrates the crucial role of HTBs for boosting electrocatalysis via the synergistic effect of TBs and strains.

Electrochemically Driven C4-Selective Decyanoalkylation of Cyanopyridines with Unactivated Alkyl Bromides Enabling C(sp3)-C(sp2) Coupling.

With cyanopyridines and alkyl bromides as coupling partners, an electrochemically driven C4-selective decyanoalkylation has been established to access diverse 4-alkylpyridines in one step. The reaction proceeds through the single electron reduction/radical-radical coupling tandem process under mild electrolytic conditions, achieving the cleavage of the C(sp2)-CN bond and the formation of C(sp3)-C(sp2). The practicality of this protocol is illustrated by no sacrificial anodes, a broad substrate scope, and gram-scale synthesis.

Enhancing coking resistance of ZSM-5 in the conversion of pine sawdust into oxygen-free bio-aromatic hydrocarbons through tandem catalytic hydropyrolysis/vapor-phase hydrotreatment

The conversion of biomass into bio-aromatic hydrocarbons is a crucial aspect of achieving sustainable development. However, inadequate deoxygenation not only reduces the yield of aromatics but also causes instability in the produced biofuels. In this study, a tandem hydropyrolysis/vapor phase hydrotreatment process was conducted in a two-stage pressurized fixed-bed reactor to produce oxygen-free bio-aromatic hydrocarbons from pine sawdust under 0.15 MPa H2 with ZSM-5. The experimental results indicated that oxygen-containing compounds generated during the hydropyrolysis of pine sawdust in the first-stage reactor, were completely hydrodeoxygenated in the second-stage reactor over ZSM-5. This resulted in a total bio-aromatic hydrocarbons yield of 109.6 mg/g, with 81.5% selectivity to monoaromatic hydrocarbons, including benzene, toluene, ethylbenzene, and xylenes (BTEXs). The optimization study revealed that the hydropyrolysis temperature, hydrodeoxygenation temperature, and catalyst-to-biomass mass ratio could be controlled at 550 °C, 450 °C, and 8:1, respectively. The tandem process, conducted under pressurized H2, showed the capability to inhibit the deactivation of ZSM-5, as the low deactivation rate (35.1%) was observed in 15 sequential experiments of pine sawdust with an accumulated catalyst-to-biomass mass ratio of 0.5. The catalytic tandem vapor-phase hydrotreatment strategy offers a promising approach to effectively produce bio-aromatic hydrocarbons from biomass.