Tandem Catalysis Research Articles

Aldehyde Directed In Situ Loading of Ag Nanodots Around the Open Metal Sites of MOFs for the Tandem Catalysis of Nitrate to Ammonia.

Both spatial arrangement and intrinsic activity of electrocatalysts with dual-active sites are widely designed to match the coupling reaction between nitrate and water, in which most of the reactive intermediates can be optimized to achieve a high yield rate of ammonia. Herein, by introducing the aldehyde group inside metal-organic frameworks (MOFs) in advance, an aldehyde-induced method is achieved to direct the in situ nucleation of Ag nanodots depending on the mesopores of MOFs via a simple silver mirror reaction. The key point here is that the spatial arrangement between the aldehyde group and open metal sites is fixed end to end, which makes the aldehyde group a built-in redox-active site to drive the in situ nucleation of Ag nanodots next to the open metal sites of MOFs. Accordingly, by varying the metal sites of MOFs, a group of M-MOFs@Ag (M = Fe, Co, Ni, Cu, etc.) hybrids with dual active sites are acquired. Taking Ni-MOFs@Ag as an example, the interaction between Ni2+ and Ag sites makes it available for the tandem catalysis of nitrate-to-ammonia, in which the H· and NO2 - generated on the open Ni2+ sites and Ag nanodots, respectively, can migrate to each other to evolve into ammonia.

Intensifying Cyclopentanone Synthesis from Furfural Using Supported Copper Catalysts.

This work addresses catalytic strategies to intensify the synthesis of cyclopentanone, a bio-based platform chemical and a potential SAF precursor, via Cu-catalyzed furfural hydrogenation in aqueous media. When performed in a single step, using either uniform or staged catalytic bed configuration, high temperature and hydrogen pressures (180 °C and 38 bar) are necessary for maximum CPO yields (37 and 49 %, respectively). Parallel furanic ring hydrogenation of furfural and polymerisation of intermediates, namely furfuryl alcohol (FFA), limit CPO yields. Employing a two step configuration with optimal catalyst bed can curb this limitation. First, the furanic ring hydrogenation can be suppressed by using milder conditions (i. e., 150 °C and 7 bar, and 14 seconds of residence time). Second, FFA hydrogenation using tandem catalysis, i. e., a mix of β-zeolite and Cu/ZrO2, at 180 °C, 38 bar and 0.6, allows sufficient time for CPO formation and minimises polymerisation of FFA, thereby resulting in 60 % CPO yield. Therefore, this work recommends a split strategy to produce CPO from furfural. Such modularity may aid in addressing flexible market needs.

Tandem Gold/Copper Catalysis and Morphological Tuning via Wrinkling to Boost CO2 Electroreduction into C2+ Products

Powered by renewable electricity, electrochemical CO2 reduction (CO2R) offers a sustainable route for the production of fuels and chemicals that are traditionally produced from fossil fuels. However, designing and developing an efficient electrocatalyst for CO2-to-C2+ product conversion remains challenging. Here, a gold-copper tandem catalyst electrode design is introduced that leverages the structural effects of a wrinkled morphology to improve the CO2R selectivity and activity in a three-electrode electrochemical cell. The wrinkled electrode structure significantly increases the electrochemical active surface area, resulting in enhanced CO2R current density for both the singular wrinkled gold and wrinkled copper electrodes. Specifically, there is a 130% increase in partial current density towards CO for a wrinkled gold electrode versus planar gold electrode at -0.7V versus the reversible hydrogen electrode (VRHE), and a 50% increase in partial current density for C2+ products for a wrinkled copper electrode at -1.05 VRHE compared to a planar copper electrode. A wrinkled gold-copper tandem electrode further enhances the partial current density of C2+ products by an additional 60% beyond that of the wrinkled copper electrode (at -1.05 VRHE), illustrating the synergistic effect of the three-dimensional wrinkled morphology combined with tandem catalysis. Tafel plot analysis revealed effective mass transport for C2+ product generation on the optimized wrinkled gold-copper tandem electrode, attributed to the local *CO production by the tandem catalyst, facilitating enhanced C-C coupling on the copper catalyst compared to a purely copper based electrode. Experimental results show that the design and manipulation of the morphology of the tandem catalyst electrode achieved via step-by-step optimization can significantly enhance the selectivity and activity of the catalyst in converting CO2 to desired fuels and chemicals.

Integration of Single Atoms for Tandem Catalysis

Integration of Single Atoms for Tandem Catalysis

Xanthate-Mediated Oxidation of Li2S as the Lithium-Containing Cathode in Lithium-Sulfur Batteries with Extremely Low Overpotential.

Lithium-sulfide (Li2S) has long been pursued as a lithium-containing cathode material for high-energy-density lithium-sulfur (Li-S) batteries. Unfortunately, its direct oxidation generally has a large overpotential, giving rise to low energy efficiency. The use of redox mediators to accelerate the conversion of solid Li2S to polysulfides represents a possible solution to lower the initial oxidation overpotential. However, most reported redox mediators exhibit significantly higher redox potentials than the desirable value. Herein, it is serendipitously found that lithium ethyl xanthate (LiEX) formed from the reaction among Li2S, ethanol, and CS2 at room temperature is an efficient redox mediator. It has a redox potential (≈2.3V vs Li+/Li) close to the electrochemical oxidation potential of Li2S (2.25V vs Li+/Li), which enables fast Li2S oxidation reaction kinetics, and more importantly, lowers the Li2S oxidation potential from ≈3.6 to ≈2.3V. When further integrated with an Ni-NC catalyst in a tandem catalysis scheme, a remarkable specific capacity of ≈1100 mAh g-1 at 0.2mA cm-2 and long cycle life of 1400 cycles with ∼73% capacity retention is achieved, outperforming those of other Li2S-based cathode materials from recent literature.

Synergetic Enzyme-Incorporated Metal-Organic Framework and Polyoxometalate Nanozyme: Achieving Stable Tandem Catalysis for Organic Photoelectrochemical Transistor Bioanalysis.

Organic photoelectrochemical transistor (OPECT) has emerged as a promising technique for biomolecule detection, yet its operational rationale remains limited due to its short development time. This study introduces a stable tandem catalysis protocol by synergizing the enzyme-incorporated metal-organic frameworks (E-MOFs) with polyoxometalate (POM) nanozyme for sensitive OPECT bioanalysis. The zeolitic imidazolate framework-8 (ZIF-8) acts as the skeleton to protect the encapsulated glucose oxidase (GOx), allowing the stable catalytic generation of H2O2. With peroxidase-like activity, a phosphotungstic acid hydrate (PW12) is then able to utilize the H2O2 to induce the biomimetic precipitation on the photogate, ultimately resulting in the altered device characteristics for quantitative detection. This work reveals the potential and versatility of an engineered enzymatic system as a key enabler to achieve novel OPECT bioanalysis, which is believed to offer a feasible framework to explore new operational rationale in optoelectronic and bioelectronic detection.

Redefining the Symphony of Light Aromatic Synthesis Beyond Fossil Fuels: A Journey Navigating through a Fe-Based/HZSM-5 Tandem Route for Syngas Conversion.

The escalating concerns about traditional reliance on fossil fuels and environmental issues associated with their exploitation have spurred efforts to explore eco-friendly alternative processes. Since then, in an era where the imperative for renewable practices is paramount, the aromatic synthesis industry has embarked on a journey to diversify its feedstock portfolio, offering a transformative pathway toward carbon neutrality stewardship. This Review delves into the dynamic landscape of aromatic synthesis, elucidating the pivotal role of renewable resources through syngas/CO2 utilization in reshaping the industry's net-zero carbon narrative. Through a meticulous examination of recent advancements, the current Review navigates the trajectory toward admissible aromatics production, highlighting the emergence of Fischer-Tropsch tandem catalysis as a game-changing approach. Scrutinizing the meliorated interplay of Fe-based catalysts and HZSM-5 molecular sieves would uncover the revolutionary potential of rationale design and optimization of integrated catalytic systems in driving the conversion of syngas/CO2 into aromatic hydrocarbons (especially BTX). In essence, the current Review would illuminate the path toward cutting-edge research through in-depth analysis of the transformative power of tandem catalysis and its capacity to propel carbon neutrality goals by unraveling the complexities of renewable aromatic synthesis and paving the way for a carbon-neutral and resilient tomorrow.

Base-acid tandem catalytic upgrading of coal pyrolysis volatiles: the effects of alkaline earth oxides and modified HZSM-5 zeolites

Catalytic upgrading of coal pyrolysis volatiles is a promising technology to bolster the production of value-added chemicals from coal. To optimize product distribution and mitigate catalyst deactivation, this work investigated tandem catalysts combining the upper alkaline earth oxides (CaO or MgO) with the lower modified HZSM-5 (mesopore creation and Ga loading). The pre-cracking of volatiles over CaO or MgO lowered the average molecule size of tar components. The diffusion properties and aromatization of these pre-cracking-derived intermediates were improved, facilitating the secondary upgrading over HZSM-5-based catalysts, promoting the formation of aromatics. The experimental results showed that tandem CaO-HZSM-5 catalysts presented better synergy to improve the tar components as compared to MgO-HZSM-5, considering the formation of aromatics in tar. In this context, the mesopore and metal Ga were introduced into HZSM-5 to further upgrade the tar quality. The mesoporous structure for HZSM-5-meso and Ga/HZSM-5-meso promoted the conversion of aliphatic hydrocarbons into aromatics. Simultaneous introduction of mesopores and Ga synergistically increased the aromatic content in tar to 41.6% and reduced the carbon deposition to 0.88wt.%. In summary, this work elucidated the mechanism of tandem CaO-modified HZSM-5 catalysis for the upgrading of volatiles from coal pyrolysis.

Heterobimetallic Synergism in Triple-Redox 2D Framework for Largely Boosted Water Oxidation and Flanked Carboxylic-Acid-Triggered Unconventional Tandem Catalysis.

A fish-bone-shaped and thermochemically stable 2D metal-organic framework (MOF) with multimodal active center-decked pore-wall is devised. Redox-active [Co2(COO)4] node and thiazolo[5,4-d]thiazole functionalization benefit this mixed-ligand MOF exhibiting electrochemical water oxidation with 375mV overpotential at 10mA cm-2 current density and 78mV per dec Tafel slope in alkaline medium. Pair of oppositely oriented carboxylic acids aids postmetalation with transition metal ions to engineer heterobimetallic materials. Notably, overpotential of Ni2+ grafted triple-redox composite reduces to 270mV with twofold declined Tafel slope than the parent MOF, ranking among the best-reported values, and outperforming majority of related catalysts. Significantly, turnover frequency and charge transfer resistance display 35.5 and 1.4-fold upsurge, respectively, with much uplifted chronopotentiometric stability and increase active surface area owing to synergistic Co(II)-Ni(II) coupling. The simultaneous presence of ─COOH and nitrogen-rich moieties renders this hydrogen-bonded MOF as acid-base synergistic catalyst for recyclable deacetalization-Knoevenagel reaction with >99% product yield under solvent-free mild condition. Besides control experiments, unique role of ─COOH as hydrogen-bond donor site in substrate activation is validated from comparing the performances of molecular-shearing approach-derived structurally similar unfunctionalized MOF, and the heterobimetallic composite. To the best of tandem Knoevenagel condensation, larger-sized acetal exhibits poor yield of α,β-unsaturated dicyanides, and demonstrates pore-fitting-mediated size-selectivity.

Noble metal-free tandem catalysis enables efficient upcycling plastic waste into liquid fuel components

The lack of effective approaches for upcycling waste plastic has led to severe environmental pollution and squandering of carbon resources. While hydrocracking macromolecular polyolefins over typical metal-zeolite catalyst produces high quality liquid fuel components, the limited activity of base metal and restricted accessibility of acid sites within microporous zeolite renders this process still not in practical scale. A tandem catalyst comprising Ni-WO3/Al2O3 and Beta zeolite was developed for consecutive hydrocracking polyolefins, achieving a yield of 86.2 % of primarily gasoline-jet ranged hydrocarbons (mainly C5-C16 and minor C16+) at 280 °C. The incorporation of tungsten species onto Ni/Al2O3 largely enhances the surface acidity and accelerates the primary cracking process that converts polyethylene (PE) into medium-sized intermediates, which would readily diffuse into the pore networks of Beta and undergo further cracking to yield desired liquid hydrocarbons. In addition, this tandem catalyst also promotes facile hydrocracking of consumer-grade plastic waste and maintains excellent stability over 5 recycling tests. The noble-metal-free catalyst achieves an impressive liquid formation rate of 5.74 g·gcat.−1·h−1, rivaling the noble metal-based catalyst and demonstrating high application prospects.

Interfacial Electronic Interactions Promoted Activation for Nitrate Electroreduction to Ammonia over Ag‐Modified Co3O4

AbstractElectrocatalytic nitrate (NO3−) reduction to ammonia (NRA) offers a promising pathway for ammonia synthesis. The interfacial electronic interactions (IEIs) can regulate the physicochemical capabilities of catalysts in electrochemical applications, while the impact of IEIs on electrocatalytic NRA remains largely unexplored in current literature. In this study, the high‐efficiency electrode Ag‐modified Co3O4 (Ag1.5Co/CC) is prepared for NRA in neutral media, exhibiting an impressive nitrate conversion rate of 96.86 %, ammonia Faradaic efficiency of 96.11 %, and ammonia selectivity of ~100 %. Notably, the intrinsic activity of Ag1.5Co/CC is ~81 times that of Ag nanoparticles (Ag/CC). Multiple characterizations and theoretical computations confirm the presence of IEIs between Ag and Co3O4, which stabilize the CoO6 octahedrons within Co3O4 and significantly promote the adsorption of reactants (NO3−) as well as intermediates (NO2− and NO), while suppressing the Heyrovsky step, thereby improving nitrate electroreduction efficiency. Furthermore, our findings reveal a synergistic effect between different active sites that enables tandem catalysis for NRA: NO3− reduction to NO2− predominantly occurs at Ag sites while NO2− tends to hydrogenate to ammonia at Co sites. This study offers valuable insights for the development of high‐performance NRA electrocatalysts.

Boosting Electroreduction of Nitrate and CO2 to Urea on a Tandem Fe1/MoS2 Catalyst.

Urea electrosynthesis by coelectrolysis of NO3- and CO2 (UENC) holds enormous promise for sustainable urea production, while the efficient UENC process relies on the rational design of high-performance catalysts to facilitate the electrocatalytic C-N coupling efficiency and the hydrogenation reaction process. Herein, Fe single atoms supported on MoS2 (Fe1/MoS2) are developed as a highly effective and robust catalyst for UENC. Theoretical calculations and operando spectroscopic measurements reveal a tandem catalysis mechanism of the Fe1-S3 motif and MoS2-edge to jointly promote the UENC process, where the Fe1-S3 motif drives the early C-N coupling and subsequent *CO2NO2-to-*CO2NH2 step. The generated *CO2NH2 is then migrated from the Fe1-S3 motif to the nearby MoS2-edge, which facilitates the *CO2NH2 → *COOHNH2 step for urea formation. Noticeably, Fe1/MoS2 assembled in a flow cell reaches a maximum urea Faraday efficiency of 54.98% with a corresponding urea yield rate of 18.98 mmol h-1 g-1, performing at the top level among all of the UENC catalysts reported to date.

Direct CO2 Methylation to Value-Added Aromatics Through Tandem Catalysis

Direct CO2 Methylation to Value-Added Aromatics Through Tandem Catalysis

A Tandem Catalysis for Isoindolinone Synthesis over Single-Atom Pd/TiO2 Catalyst.

Developing an efficient strategy to replace the conventional synthesis method for producing isoindolinone (IIO) scaffold, a crucial structural motif for constructing pharmaceutical molecules, remains to be a great challenge. Herein, a single-atom Pd/TiO2 tandem catalysis has been developed for the IIO scaffold synthesis by using readily available phthalic anhydride (PA), ammonia, and H2. The single-atom Pd/TiO2 catalyst demonstrates superior catalytic performance, achieving a PA conversion of 99 %, an IIO selectivity of 91 %, and a turnover frequency (TOF) up to 4807 h-1. This exceptional performance can be attributed to the tandem catalysis between TiO2 support and single-atom Pd. The TiO2 efficiently catalyzes the conversion of PA with ammonia to form phthalimide (PAM), subsequently transformed into IIO over TiO2 through the reaction of PAM with NH3 and the spillover hydrogen species derived from single-atom Pd. Notably, NH3 functions not only as a reactant but also as a promoter to accelerate the reduction of amides combined with the Pd/TiO2 catalyst. This tandem catalysis of a single-atom Pd/TiO2 catalyst provides a promising strategy for the synthesis of the crucial IIO platform molecules.

Tandem Effect Promotes MXene‐Supported Dual‐Site Janus Nanoparticles for High‐Efficiency Nitrate Reduction to Ammonia and Energy Output through Zn‐Nitrate Battery

AbstractElectrocatalytic nitrate reduction reaction (NO3RR) can convert nitrate contaminants into ammonia with higher added value. However, due to the NO3RR involving complex multi‐electron reactions, there is an urgent need to develop efficient electrocatalysts. Herein, CoCu Janus nanoparticles loaded on Ti3C2Tx MXene (CoCu‐Ti3C2Tx) is synthesized via the combination of molten salt etching and galvanic replacement strategy. The tandem catalysis of CoCu Janus NPs can maintain the balance between nitrogenous intermediates and active hydrogen (Hads). CoCu‐Ti3C2Tx exhibits a high NH3 yield of 8.08 mg h−1 mgcat.−1 and a satisfactory Faradaic efficiency of 93.6% at −0.7 V versus reversible hydrogen electrode (RHE). The Zn‐NO3− battery assembled with CoCu‐Ti3C2Tx shows an excellent power density of 10.33 mW cm−2, an NH3 yield of 1.52 mg h−1 mgcat.−1 and a Faradaic efficiency of 95.3% at 10 mA cm−2, which enables the simultaneous elimination of nitrate pollutants, ammonia production, and energy supply. Moreover, a series of verification experiments and density functional theory calculation are combined to reveal the reaction path and tandem catalytic mechanism. This work not only provides a new inspiration for the design of tandem catalysts but also promotes the development of Zn‐nitrate battery.

Accelerated Solar-Driven Polyolefin Degradation via Self-Activated Hydroxy-Rich ZnIn2S4.

Degradation of polyolefin (PE) plastic by a traditional chemical method requires a high pressure and a high temperature but generates complex products. Here, sulfur vacancy-rich ZnIn2S4 and hydroxy-rich ZnIn2S4 were rationally fabricated to realize photocatalytic degradation of PE in an aqueous solution under mild conditions. The results reveal that the optimized photocatalyst could degrade PE into CO2 and CO, and PE had a weight loss of 84.5% after reaction for 60 h. Systematic experiments confirm that the synergetic effect of hydroxyl groups and S vacancies contributes to improve the photocatalytic degradation properties of plastic wastes. In-depth investigation illustrates that the active radicals attack (h+ and •OH) weak spots (C-H and C-C bonds) of the PE chain to form CO2, which is further selectively photoreduced to CO. Multimodule synergistic tandem catalysis can further improve the utilization value of plastic wastes; for example, product CO2/CO in the plastic degradation process can be converted in situ into HCOOH by coupling with electrocatalytic technology.

Cover Feature: Hydroformylation of Olefins with CO2/H2 and Hydrosilane by Copper/Cobalt Tandem Catalysis (ChemSusChem 16/2024)

Cover Feature: Hydroformylation of Olefins with CO₂/H₂ and Hydrosilane by Copper/Cobalt Tandem Catalysis (ChemSusChem 16/2024)

Chemoselective and Triggered Decomposition of Diazo Esters by the [(IMes)Rh2(OAc)4] Complex: En Route to Assisted Tandem Catalysis from Mixtures of Diazo Compounds

AbstractDecomposition of aryl and unsubstituted diazo ester into Rh(II)‐carbenes by the [(IMes)Rh2(OAc)4] complex is shown to be slower than with Rh2(OAc)4. Diazo esters substituted by a second electron‐withdrawing group do not suffer nitrogen extrusion when exposed for several hours to this (NHC)Rh(II) complex at room temperature. This chemoselective decomposition of diazo esters depending on their substituent (Ar, H, EWG) can furthermore be achieved on a mixture of substrates. The catalytic activity of [(IMes)Rh2(OAc)4] towards electron‐poor diazo compounds is also restored by heating to reflux in chloroform, or after decomplexation of the NHC by addition of GaCl3. The [(IMes)Rh2(OAc)4] complex was then used to induce a fully selective reaction cascade from a mixture of two diazo esters. First, a donor/acceptor diazo compound was decomposed selectively at room temperature to give an intermolecular O−H insertion product without any decomposition of the electron poor diazo compound. Addition of GaGl3 then triggered nitrogen extrusion from the diazo malonate to give a 1,5‐C−H insertion product. This transformation, where decomposition of diazo compounds catalyzed by Rh(II) complexes can be externally controlled, represents the first example of assisted tandem catalysis with two metal carbene precursors.

Tuning the size and spatial distribution of Pt in bifunctional Pt-zeolite catalysts for direct coupling of ethane and benzene

Controlling the dispersion and position of metal active sites in bifunctional metal–acid zeolite catalysts is essential for achieving synergy between the metal and acid sites in tandem catalytic processes, but still challenging nowadays. Herein, we propose an approach to modulate the dispersion and position of Pt particles in ZSM-5 zeolite by employing various types of organic structure-directing agents (OSDAs) in the one-pot synthesis procedure. Systematic characterizations show that the OSDAs mainly influence the encapsulation of the Pt precursor into the ZSM-5 zeolite crystallites during the hydrothermal crystallization process, resulting in discrepancies in the dispersion and spatial distribution of Pt sites in the final Pt-zeolite catalysts. Comparative studies on different Pt-zeolite catalysts show that the formation of subnanometer Pt clusters and the close spatial proximity of Pt and Brønsted acid sites in the zeolite efficiently promote the tandem dehydrogenation-alkylation process and enhance the production rate of ethylbenzene in the direct ethane-benzene coupling reaction. This study offers insights into the design and synthesis of bifunctional metal-zeolite catalysts for tandem catalysis.

An Intramolecular Reaction between Pyrroles and Alkynes Leads to Pyrrole Dearomatization under Cooperative Actions of a Gold Catalyst and Isoxazole Cocatalysts.

The gold-catalyzed one-pot synthesis of 3H-benzo[e]isoindoles (3) from a mixture of isoxazole (2) and diynamides (1) is described. This tandem catalysis involves two separate steps: (i) initial synthesis of 2-(3-pyrrolyl)-1-alkynylbenzenes and (ii) a novel alkyne/pyrrole coupling reaction through pyrrole dearomatization. Our control experiments reveal the cooperative action of the gold catalyst and isoxazole cocatalyst to enable the novel alkyne/pyrrole coupling leading to a 1,2-acyl shift.