Catalytic Process Research Articles

In-situ Reconstruction of Catalyst in Electrocatalysis.

Reconstruction of catalysts is now well recognized as a common phenomenon in electrocatalysis. As the reconstructed structure may promote or hamper the electrochemical performance, how to achieve the designed active surface for highly enhanced catalytic activity through the reconstruction needs to be carefully investigated. In this review, the genesis and electrochemical effects of reconstruction in various electrochemical catalytic processes, such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), carbon dioxide reduction reaction (CO2RR), and nitrate reduction reaction (NO3RR) are first described. Then, the strategies for optimizing the reconstruction, such as valence states control, active phase retention, phase evolution engineering, and surface poisoning prevention are comprehensively discussed. Finally, the general rules of reconstruction optimization are summarized and give perspectives for future study. It is believed that the review shall provide deep insights into electrocatalytic mechanisms and guide the design of pre-catalysts with highly improved activity.

Designing Robust Single Atom Catalysts by Three-in-One Strategy: Sub-1-nm Space Confining, Bimetallic Bonding and Reaction-Induced Forming Active Sites.

It is imperative to design robust single atom catalysts (SACs) that maintain the stability of the active component under diverse reaction conditions and prevent aggregation or deactivation. Confining the single atom active site within sub-nanometer (sub-1-nm) spaces has proven effective in enhancing the stability and activity of the catalyst, owing to the strong constraints and regulations imposed on atomic behavior at this scale. Bimetallic bond atomic sites, comprising two distinct metal compositions, often exhibit unique electronic structures and catalytic properties. Designing SACs under reaction-induced conditions, such as varying temperatures, pressures, and atmospheres, can facilitate a deeper understanding of the formation and migration behavior of active sites in real reactions, as well as the optimization mechanisms for performance enhancement. The objective of this review is to promote a robust SAC design strategy that encapsulates bimetallic bonding active sites within sub-1-nm spaces and investigates catalyst preparation and performance under reaction-induced conditions. This design strategy is anticipated to bolster the catalytic activity and stability of the catalyst while also offering fresh perspectives and optimization avenues for the catalytic processes involved in practical chemical reactions.

Computer-Aided Flexible Loops Engineering of Glutamate Dehydrogenase for Asymmetric Synthesis of Chiral Pesticides l-phosphinothricin.

The access to the enantiopure noncanonical amino acid l-phosphinothricin (l-PPT) by applying biocatalysts is highly appealing in organic chemistry. In this study, a NADH-dependent glutamate dehydrogenase from Lachnospiraceae bacterium (LbGluDH) was chosen for the asymmetric synthesis of l-PPT. Three flexible loops undergoing big conformational shifts during the catalysis were identified and rationally engineered following the initial mutagenesis. The enzyme's specific activity toward the key precursor of l-PPT, 2-oxo-4-[(hydroxy) (methyl) phosphinyl] butyric acid (PPO), was improved from negligible to 9 U/mg, and the Km value was reduced to 17 mM. The computational analysis showed that the modified loops broadened the enzyme's narrow tunnels, allowing the substrate to access the binding pocket and get closer to the crucial residue D165, thereby enhancing the catalytic process. Utilizing the variant as the catalyst, the preparation of l-PPT achieved a 100% conversion rate within 60 min, coupled with a stereoselectivity exceeding 99.9%, demonstrating its practical capacity for industrial application. Similar enhancement in catalytic activity was obtained applying the same strategy to a typical NADH-dependent GluDH from Pyrobaculum islandicum (PisGluDH), indicating the effectiveness of our strategy for the protein engineering of GluDHs targeted to the biosynthesis of unnatural compounds.

Utilization of sterculia foetida oil as a sustainable feedstock for biodiesel production: optimization, performance, and emission analysis

This study examines the feasibility of employing Sterculia foetida oil as a sustainable feedstock for biodiesel production, offering an eco-friendly substitute for conventional diesel fuel without requiring engine alterations. The method employs a two-step catalytic process, first with acid esterification to reduce the free fatty acid (FFA) concentration, followed by alkaline esterification for biodiesel synthesis. Essential process parameters—such as reaction time, temperature, catalyst concentration, and molar ratio—are carefully optimized to improve biodiesel yield. Under optimal conditions, the process achieves an impressive conversion rate of 95.2 %, demonstrating the considerable potential of Sterculia foetida oil for biodiesel production. Furthermore, blends of Sterculia foetida biodiesel (SFB) and diesel demonstrate a notable decrease in harmful emissions, especially a 2.3 % reduction in carbon monoxide (CO), a 4.1 % reduction in hydrocarbons (HC), and a 1.9 % decrease in smoke emissions compared to pure diesel. This study highlights the innovative use of non-edible oil as feedstock, a customized optimization method, and a highly effective catalytic process, all while emphasizing environmental sustainability and reduced emissions.

Catalytic Synthesis of 1H-Benzoxazolo[3,2-a]pyridin-1-ones via Formal [3 + 3] Annulations of NHC-Generated Alkynyl Acylazoliums with Benzoxazolyl Acetates and Their Photophysical Studies.

We disclose the synthesis of a tricyclic fused N-heterocycle via the NHC-catalyzed annulation of either a ynal or an alkynyl ester with readily accessible benzoxazolyl acetate. While the annulation with ynals requires an oxidant, the reaction with alkynyl esters proceeds via the direct generation of alkynyl acylazolium intermediates with an NHC. With the dearth of catalytic processes to access these 1H-benzoxazolo[3,2-a]pyridin-1-ones from simple starting materials, this method is especially important. The photophysical properties of the products have also been evaluated.

Second Generation Zwitterionic Aza‐Diarylethene: Photoreversible CN Bond Formation, Three‐State Photoswitching, Thermal Energy Release, and Facile Photoinitiation of Polymerization

Diarylethenes are a well‐studied and optimized class of photoswitches with a wide range of applications, including data storage, smart materials, or photocontrolled catalysis and biological processes. Most recently, aza‐diarylethenes have been developed in which carbon‐carbon bond connections are replaced by carbon‐nitrogen connections. This structural elaboration opens an entire new structure and property space expanding versatility and applicability of diarylethenes. In this work, we present the second generation of zwitterionic aza‐diarylethenes, which finally allows for fully reversible photoswitching and precise control over all three switching states. High‐yielding photoswitching between the neutral open form and a zwitterionic Z isomer is achieved with two different wavelengths of light. The third zwitterionic E isomeric state can be reached up to 87% upon irradiation with a third wavelength. Its high energy content of >10 kcal/mol can be released thermally by deliberate solvent change as trigger mechanism, rendering aza‐diarylethenes into interesting candidates for molecular solar thermal energy storage (MOST) applications. The third state further serves as locking state, allowing to toggle light‐responsiveness reversibly between thermally labile and thermally stable switching. Further, irradiation of the zwitterionic states leads to highly efficient photopolymerization of methyl acrylate (MA), directly harnessing the unleashed chemical reactivity of aza‐diarylethene in materials applications.

Second Generation Zwitterionic Aza-Diarylethene: Photoreversible CN Bond Formation, Three-State Photoswitching, Thermal Energy Release, and Facile Photoinitiation of Polymerization.

Diarylethenes are a well-studied and optimized class of photoswitches with a wide range of applications, including data storage, smart materials, or photocontrolled catalysis and biological processes. Most recently, aza-diarylethenes have been developed in which carbon-carbon bond connections are replaced by carbon-nitrogen connections. This structural elaboration opens an entire new structure and property space expanding versatility and applicability of diarylethenes. In this work, we present the second generation of zwitterionic aza-diarylethenes, which finally allows for fully reversible photoswitching and precise control over all three switching states. High-yielding photoswitching between the neutral open form and a zwitterionicZisomer is achieved with two different wavelengths of light. The third zwitterionicEisomeric state can be reached up to 87% upon irradiation with a third wavelength. Its high energy content of >10 kcal/mol can be released thermally by deliberate solvent change as trigger mechanism, rendering aza-diarylethenes into interesting candidates for molecular solar thermal energystorage (MOST) applications. The third state further serves as locking state, allowing to toggle light-responsiveness reversibly between thermally labile and thermally stable switching. Further, irradiation of the zwitterionic states leads to highly efficient photopolymerization of methyl acrylate (MA),directly harnessing the unleashed chemical reactivity of aza-diarylethene in materials applications.

Research on Non-Equilibrium Dynamics Theory in Chemical Thermodynamics

Non-equilibrium dynamics theory is an important branch of chemical thermodynamics, widely applied in describing complex chemical reaction systems far from equilibrium. With the advancement of modern science and technology, an increasing number of chemical reactions exhibit unique behaviors under non-equilibrium conditions, such as self-organization and periodic oscillations—nonlinear phenomena. This paper systematically explores the distinctions between non-equilibrium and equilibrium states, introduces the fundamental principles of non-equilibrium thermodynamics, and analyzes cutting-edge issues such as nonlinear phenomena and multi-scale dynamics. Additionally, it discusses the specific applications of non-equilibrium dynamics in far-from-equilibrium reactions, heterogeneous catalysis, and industrial chemical processes, addressing both theoretical and experimental challenges. Through the combination of theoretical analysis and practical application, this paper aims to provide new insights and methodologies for research on non-equilibrium dynamics in the field of chemistry.

Ionic liquid catalysts for dehydrochlorination: Stability, reaction mechanism, and catalyst optimization

The catalytic alkaline dehydrochlorination process, characterized by high atom economy, stands as a prevalent method in the synthesis of valuable alkene halides. Nonetheless, the efficacy of ionic liquids (ILs) as catalysts for dehydrochlorination is hindered by challenges such as swift deactivation attributed to decomposition and reduced selectivity without clear causative factors. This investigation employs a systematic approach, integrating Density Functional Theory (DFT) simulations with experimental methodologies, to delve into the mechanisms of IL-catalyzed dehydrochlorination, aiming to elucidate both stabilization strategies and catalytic pathways. The examination of thermal decomposition rates is rooted in a meticulous assessment of the energy barriers associated with decomposition and dissociation processes. The active role of free Cl− is established, albeit its acidification by HCl, which results in diminished catalytic activity. To counteract this acidifying influence, a novel active site denoted as [Cl-KCl]− is conceptually devised to mitigate such effects. Through the strategic implementation of cationic fixation, the IL-KCl combination catalyst is synthesized and empirically confirmed to demonstrate augmented acid resistance while upholding a consistent reaction selectivity of approximately 85 %. This contrasts starkly with the declining catalytic selectivity observed with IL in isolation, plummeting from 85% to 65%. Consequently, the IL-KCl combination catalyst emerges as a promising option for alkali catalyzed dehydrochlorination, offering enhanced stability and sustained high selectivity throughout the catalytic process.

Zirconium Phosphates and Phosphonates: Applications in Catalysis

This review covers recent advancements in the use of zirconium phosphates and phosphonates (ZrPs) as catalysts or catalyst supports for a variety of reactions, including biomass conversion, acid–base catalysis, hydrogenation, oxidation, and C-C coupling reactions, from 2015 to the present. The discussion emphasizes the intrinsic catalytic properties of ZrPs, focusing on how surface acidity, hydrophobic/hydrophilic balance, textural properties, and particle morphology influence their catalytic performance across various reactions. Additionally, this review thoroughly examines the use of ZrPs as supports for catalytic species, ranging from organometallic complexes and metal ions to noble metals and metal oxide nanoparticles. In these applications, ZrPs not only enhance the dispersion and stabilization of active catalytic species but also facilitate their recovery and reuse due to their robust immobilization on the solid support. This dual functionality underscores the importance of ZrPs in promoting efficient, selective, and sustainable catalytic processes, making them essential to the advancement of green chemistry.

High‐Pressure Cell for In Situ Grazing Incidence XAS Characterization of Model Catalysts on Planar Supports

AbstractThe growing interest in physically deposited model catalysts for uncovering complex structure‐activity relationships is spurred by the possibility of depositing nanoparticles of precise atomic structure and composition using cluster‐beam sources. However, the limitations accompanying these synthesis techniques, such as low deposition rates and flat sample geometry, present a challenge for in situ structural characterization using bulk‐sensitive methods, such as X‐ray absorption spectroscopy (XAS), especially at elevated pressures (1–100 bar). To overcome this challenge, we constructed an in situ XAS cell operating in a grazing incidence (GI) geometry. The GIXAS cell was used to investigate the structure of cluster‐beam‐generated Pd and Au0.3Ag0.7 nanoparticles under CO2‐to‐methanol hydrogenation conditions (230 °C, 20 bar, CO2:H2=1 : 3). These nanoparticles, with metal loading of 0.96–10 μg cm−2, demonstrated stability and resistance to sintering upon activation in H2 at 120 °C and catalytic conditions, revealed by in situ XAS. The promising results from our work will help bridge the gap in the investigation of model catalytic materials produced by gas‐phase cluster deposition at industrially relevant pressures and temperatures, which is vital for a mechanistic understanding of catalytic processes.

In‐Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water‐Gas Shift Reaction

AbstractIn situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water‐gas shift (RWGS) reaction. Surface oxygen atoms in various Mo‐based catalysts are removed in H2‐containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt‐dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal−1 ⋅ h−1 at 600 °C has been achieved over in situ carbonized H‐intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

Comparative Study of Porous High‐Entropy Oxides as Low‐Temperature Catalysts for CO2 Methanation

AbstractHigh‐entropy oxides (HEOs) are an emerging class of materials whose compositional complexity has garnered attention because of their tailorable chemistries and unique properties arising from extreme configurational entropy. Solid‐state methods are often employed to synthesize HEOs, but such methods result in poor material properties for catalytic processes, leaving HEOs less studied for catalysis. Here we utilize different wet‐synthesis strategies to produce porous HEOs and investigate their performance in heterogeneous CO2 hydrogenation to methane. Specifically, HEOs were synthesized using hydrothermal, co‐precipitation, and solvothermal methods, resulting in different morphologies like platelets or spheres. Of the tested materials, HEOs with 2‐D platelets derived from hydrothermally‐synthesized high‐entropy layered double hydroxides had superior catalytic performance, especially in low‐temperature regimes (<300 °C). K‐edge XANES indicated that metallic sites (Ni0‐Co0) were formed during the reaction, and these metallic sites are dispersed into the HEO matrix which is confirmed by STEM/elemental mapping. This facile synthesis approach allows for realized synergy between the metallic sites and the HEO support, leading to superior performance for CO2 methanation compared to low‐entropy counterparts. Finally, this study illustrates how HEOs offer new avenues of tailorability in terms of the interplay between support, active site and reaction temperatures for heterogeneous catalysis.

In-Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water-Gas Shift Reaction.

In situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water-gas shift (RWGS) reaction. Surface oxygen atoms in various Mo-based catalysts are removed in H2-containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt-dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal -1 ⋅ h-1 at 600 °C has been achieved over in situ carbonized H-intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

Reversible Grafting in Surface Organometallic Chemistry with a Late Transition‐Metal Amidinate Precursor

Supported catalysts are central to industrial catalytic processes. While traditional synthesis methods often yield poorly defined materials, thus complicating structural elucidation, Surface Organometallic Chemistry (SOMC) offers a solution, producing well‐defined structures. Recent advances in SOMC precursor development have shown that amidinate‐based precursors are a privileged class of precursors to generate supported metallic nanoparticles. In that context, this study investigates the grafting mechanism of a prototypical amidinate precursor, Ir(COD)(DIA) (1‐Ir), onto SiO2. Unique to amidinate complexes, grafting is shown to occur without ligand release, creating a reversible covalent bond. Using Ir‐TBOS as a molecular analogue, the structure of the grafted species and the reversibility of the reaction with O‐H groups are demonstrated using IR spectroscopy, single X‐Ray diffraction, variable‐temperature NMR spectroscopy, X‐Ray absorption spectroscopy (XAS), and supported by DFT calculations. Notably, we show that a partial degrafting is also possible at elevated temperatures under vacuum

Engineered Multifunctional BioHJzyme via Tuning D‐Band Center for Postoperative Infected Wound Regeneration of Tumor Resection

AbstractThe catalytic therapy for abundant •OH, 1O2, and •O2− provides an efficient tactic and methodology for rapid tumor/bacteria killing, whereas the limitation is focused on the catalytic efficiency owing to the in‐built energy band of catalytic materials. Thus, d‐band center tuning BioHJzyme is devised, which is composed of zinc tellurate/manganese dioxide anchored by glucose oxidase (GOx) with anti‐tumor and anti‐bacteria properties for postoperative infected wound regeneration of tumor. The GOx depletes glucose to produce H2O2, intercepting the glucose metabolism. The D‐BioHJzyme can catalyze the produced H2O2 to highly lethal •OH with POD‐mimetic activity owing to the tunned d‐band center strategy decreasing the adsorption energy of the intermediate in the catalytical process, while the oxygen originated from H2O2 and Mn2+ can be catalyzed into 1O2. The GPx‐mimetic activity of it can impair the antioxidant system of tumor. In vivo studies show that the BioHJzyme exhibits robust abilities against bacteria and tumors by •OH/1O2 production and promotes the apoptosis owing the Te. Besides, the BioHJzyme can accelerate cutaneous regeneration by M1/M2 regulation and the angiogenesis/collagen deposition. This work enlightens a powerful platform for the remedy of postoperative infected wound regeneration of tumor resection using an engineered BioHJzyme.

Characterization of sugar maple and red oak bark: Efficient lignin extraction via the Organosolv and acidic dioxane process

The barks of two wood species, sugar maple (SM) and red oak (RO), were investigated to characterize their chemical composition and isolate the lignins they contain, representing relatively underexplored and underutilized polymers. Characterizing these two barks involved assessing extractive components, Klason and acid-soluble lignin, ash content, and sugars. It was observed that RO bark had a higher concentration of extractive substances and a lower Klason lignin content compared to SM bark. The Klason lignin content in the barks of the SM and RO bark was measured at 35.0% and 26.4%, respectively, higher than values reported for corresponding to wood of the same species, 21.8% and 22.2%, respectively, for RO and SM. Lignin isolation from bark was achieved by utilizing Organosolv catalytic and acid dioxane processes. Notably, the Organosolv process yielded lignins of considerably higher purity. The structural analysis of the bark lignins was peformed by combination of spectroscopic methods: FTIR,13P NMR, and solid-state NMR. Compared to dioxane lignins, a higher concentration of OH bound to syringyl and guayacyl units were found in Organosolv lignins. In contrast, aliphatic OH units are more important in dioxane lignins than in Organosolv lignins. Furthermore, sugar analysis was conducted via HPLC, thermal analysis was conducted through DSC and TGA, and ash composition identification was done using ICP-OES. Notably, higher Mw and Mn values are determined by GPC for dioxane lignins than for Organosolv lignins.

Ring‐opening copolymerization of ε‐caprolactone and δ‐valerolactone to cyclic polyesters by a bimolecular system

AbstractBio‐based plastics have received much attraction because they are an alternative to petroleum‐based plastics in recent years. Among them, aliphatic polyesters have garnered the most attention due to their excellent properties. Polyester is primarily synthesized through ring opening polymerization of monomer, and the catalysts used are mostly synthesized through “click” reaction in the laboratory, which exhibits inferior activity and little commercial value. Herein, a facile approach was developed for the synthesis of high molecular‐weight cyclic aliphatic polyesters, specifically poly(valerolactone‐co‐caprolactone) with varying compositions. This involved the ring‐opening copolymerization of ε‐caprolactone (ε‐CL) and δ‐valerolactone (δ‐VL) in the absence of an initiator with commercial hydrogen bond donor triclorocarban and an organic base. The structure and properties of the prepared cyclic polyester were investigated using GPC, 13C NMR, 1H NMR, MALDI‐TOF mass spectrometry, TOF‐SIMS mass spectrometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD) techniques. The results show that the molecular weight of cyclic polyester can rapidly exceed 40 kDa, with a PDI of approximately 1.10. In comparison to linear polyester, it has a higher melting point and superior thermodynamic properties, thus presenting greater application potential. Finally, based on nuclear magnetic resonance titration, the potential catalytic processes and mechanisms of bimolecular systems on monomers in different environments were discussed. This study not only offers new insights into the structure and properties of cyclic polyesters, but also presents novel bimolecular catalytic systems using commercial urea hydrogen bond donors for the synthesis of cyclic polymer polyesters.

Machine Learning-Enhanced Screening of Single-Atom Alloy Clusters for Nitrogen Reduction Reaction.

The electrochemical nitrogen reduction reaction (eNRR) under ambient conditions is a promising method to generate ammonia (NH3), a crucial precursor for fertilizers and chemicals, without carbon emissions. Single-atom alloy catalysts (SAACs) have reinvigorated catalytic processes due to their high activity, selectivity, and efficient use of active atoms. Here, we employed density functional theory (DFT) calculations integrated with machine learning (ML) to investigate dodecahedral nanocluster-based SAACs for analyzing structure-activity relationships in eNRR. Over 300 nanocluster-based SAACs were screened with all the transition metals as dopants to develop an ML model predicting stability and catalytic performance. Facet sites were identified as optimal doping positions, particularly with late group transition metals showing superior stability and activity. Utilizing DFT+ML, we identified 8 highly suitable SAACs for eNRR. Interestingly, the number of valence d-electrons in dopants proved crucial in screening for eNRR activity. These catalysts exhibited low activity in hydrogen evolution reaction, further enhancing their suitability for eNRR. This successful ML-driven approach accelerates catalyst design and discovery, holding significant practical implications.

Application of Hydrogen Spillover to Enhance Alkaline Hydrogen Evolution Reaction

AbstractAlkaline water splitting has shown great potential for industrial‐scale hydrogen production. However, its broad application is constrained by hydrogen evolution reaction (HER) electrocatalysts, which struggle to achieve optimal current density at low overpotential. The utilization of the hydrogen spillover effect to augment the performance of HER represents a burgeoning area of research. Although previous studies mainly focused on hydrogen spillover in acidic media, the latest studies have shown that hydrogen spillover also exists under alkaline conditions, and its role in improving HER performance cannot be ignored. This review examines the mechanisms of HER under acidic and alkaline conditions, elucidating the distinctive behavior of hydrogen spillover in these environments and its influence on catalytic processes. At the same time hydrogen spillover characterization methods are systematically summarized, these technologies for understanding and control of hydrogen release process provides strong support. Finally, the recent electrocatalysts that enhance the catalytic performance of alkaline HER by hydrogen spillover effect are comprehensively sorted out and summarized. This review not only demonstrate the practical value of hydrogen spillover under alkaline conditions, but also provide new directions for future design and optimization of electrocatalysts.