Efficient and Stable pH-Universal Water Electrolysis Catalyzed by N-Doped Hollow Carbon Confined RuIrOx Nanocrystals.

A facile strategy is developed to fabricate 3 nm RuIrOx nanocrystals anchored onto N-doped hollow carbon for highly efficient and pH-universal overall water splitting and alkaline seawater electrolysis. The designed catalyst exhibits much lower overpotential and superior stability than most previously reported Ru- and Ir-based electrocatalysts for hydrogen/oxygen evolution reactions. It also manifests excellent overall water splitting activities and maintains ≈100% Faradic efficiency with a cell voltage of 1.53, 1.51, and 1.54 V at 10 mA cm-2 for 140, 255, and 200 h in acid, alkaline, and alkaline seawater electrolytes, respectively. The excellent electrocatalytic performance can be attributed to solid bonding between RuIrOx and the hollow carbon skeleton, and effective electronic coupling between Ru and Ir, thus inducing its remarkable electrocatalytic activities and long-lasting stability.

A Systematic Study of Nonionic Di- and Multiborane Catalysts for the Oligomerization and Polymerization of Epoxides.

Borane catalysis has emerged as a powerful technology in epoxide polymerization. Still, the structure-activity correlations for these catalysts are not fully understood to date, especially regarding compounds with nonionic backbones. Thus, in this work, 13 different borane catalysts of this respective type are described and investigated for their epoxide oligomerization and polymerization performance, using propylene oxide (PO), 1-butylene oxide (BO) and allyl glycidyl ether (AGE) as monomers. Structurally, special emphasis is put on catalysts with different linker lengths and linker flexibilities as well as the introduction of more than two borane functionalities. Importantly, this screening is conducted both under typical polymerization conditions as well as under the chain transfer agent (CTA)-rich conditions relevant for large-scale production. It is found that suitable preorganization of the borane groups, such as present in biphenyl derivatives, offers a simple route to high-performing catalysts and quantitative monomer conversion of the investigated epoxides. Furthermore, it is demonstrated that a diborane-catalyzed oligomerization can be kept active over weeks, whereby repeated addition of monomer batches (14 steps) constantly results in full conversion and well-defined oligoethers, underlining the practical potential of this method. The absence of co-initiating counter ions is suggested as an inherent advantage of nonionic catalysts.

The Diversity and Evolution of Chiral Brønsted Acid Structures.

The chemical space of chiral Brønsted acid catalysts is defined by quantity and complexity, reflecting the diverse synthetic challenges confronted and the innovative molecular designs introduced. Here, we detail how this successful outcome is a powerful demonstration of the benefits of utilizing both local structure searches and a comprehensive understanding of catalyst performance for effective and efficient exploration of Brønsted acid properties. In this concept article we provide an evolutionary overview of this field by summarizing the approaches to catalyst optimization, the resulting structures, and functions.

Expedited Proton Relay in Enzyme-Inspired Cobaloximes Facilitate Organic Transformations.

Developing a water-soluble, oxygen-tolerant, and acid-stable synthetic H2 production catalyst is vital for renewable energy infrastructure. To access such an effective catalyst, we strategically incorporated enzyme-inspired, multicomponent outer coordination sphere elements around the cobaloxime (Cl-Co-X) core with suitable axial coordination (X). Our cobaloximes with axial imidazole or L-histidine coordination in photocatalytic HAT including the construction of anilines via a non-canonical cross-coupling approach is found superior compared to commonly used cobaloxime catalysts. The reversible Co(II)/Co(I) process is influenced by the axial N ligand's nature. Imidazole/L-histidine with a higher pKa promptly produces H2 upon irradiation, leading to the improved reactivity compared to previously employed axial (di)chloride or pyridine analogue.

Effects of the Carbon Support on Heterogeneous Molecular Catalysts for Carbon Dioxide Reduction.

Molecular catalysts stabilized on a support material, also called heterogeneous molecular catalysts, exhibit excellent performance in carbon dioxide reduction reaction (CO2 RR). Different support in these electrocatalysts can have a substantial influence on the activity, making support control one tool to enhance the CO2 RR performance. However, a systematic understanding of the support effects is lacking. Taking cobalt phthalocyanine (CoPc) immobilized onto different carbon materials as examples, we demonstrate that the surface area, pore structure and the morphology of the as-prepared heterogeneous molecular catalysts can influence the CO2 transfer and adsorption, and then change the CO2 RR activity. In contrast to the other four materials, CoPc/mesoporous carbon (MC) can efficiently convert carbon dioxide to carbon monoxide at minimal overpotential (-0.8 V vs. RHE) due to its special nanostructure and pore distribution. The results of this study suggest that the performance of electrocatalytic reduction of carbon dioxide can be improved by changing different substrates.

Biobased Heterogeneous Renewable Catalysts: Production Technologies, Innovations, Biodiesel applications and Circular Bioeconomy.

The growing population and waste biomass accumulation are leading to increased environmental pollution and climate change. Waste biomass comprising different components has promising potential to produce value-added products for sustainable environmental solutions. This review explores the critical role of bio-based heterogeneous catalysts in enabling sustainable waste biomass utilization. In industrial chemical transformations, over 95% involve catalysts, with more than 90% being heterogeneous systems, prized for their robustness, ease of product separation, and reusability. Bio-based heterogeneous catalysts address the pressing need for sustainable waste biomass management, allowing the conversion of diverse waste biomasses into biodiesel as valuable products. Research on these catalysts, particularly for biodiesel production, has shown yields exceeding 90% with enhanced catalyst reusability. This surge in research is evident from the increasing number of published articles, notably in 2022 and 2023, highlighting growing interest and importance in the scientific community. The synthesis of these catalysts is examined, including novel approaches and techniques to enhance their efficiency, selectivity, and stability. The challenges with their feasible solutions of heterogeneous catalysts in catalyst-based processes are addressed. Altogether, this review underscores the immense potential of bio-based heterogeneous catalysts in sustainable waste biomass utilization, aligning with resource efficiency and environmental conservation goals while offering distinct insights and perspectives on the latest innovations in the field.

Breakthrough in CO2 Electroreduction to Multi-Carbon Products at Ampere-Level Enabled by Active Sites Engineering.

Efficient production of value-added chemicals with high selectivity from CO2 electroreduction at industrial-level current density is highly demanded, yet remains a big challenge. In a recent issue of Angewandte Chemie, Han and colleagues have elegantly increased the Faradaic efficiency (FE) of multi-carbon (C2+) products to over 70% at amperes level (1.4 A cm-2) by engineering the active sites for the key reactions involved in the CO2 electroreduction. In this study, the highly dispersed Pd atoms have two unique functions: active sites for water dissociation and to induce the electron rearrangement of the surrounding Cu atoms to form new active sites for CO conversion, while the Cu far from Pd are the active sites for efficient CO2 conversion to CO, the synergistic functions of these three active sites result in high FE and yields of C2+ products at industrial-level current density. This research is a remarkable step forward in the methodology for developing efficient and durable catalysts for CO2 electroreduction and beyond.

Design, Preparation, and Implementation of Axially Chiral Benzotetramisoles as Lewis Base Catalysts for Asymmetric Cycloadditions.

Developing novel catalysts with potent activity is of great importance in organocatalysis. In this study, we designed and prepared a new class of benzotetramisole Lewis base catalysts (AxBTM) that have both central and axial chirality. This unique feature of these catalysts results in a three-dimensional microenvironment with multi-layers of chirality. The performance of the developed catalysts was tested in a series of cycloaddition reactions. These included the AxBTM-catalyzed (2+2) cycloaddition between α-fluoro-α-aryl anhydride with imines or oxindoles, and the sequential gold/AxBTM-catalyzed (4+2) cycloaddition of enynamides with pentafluorophenyl esters. The interplay between axial and central chirality had a collaborative effect in regulating the stereochemistry in these cycloadditions, leading to high levels of stereoselectivity that would otherwise be challenging to achieve using conventional BTM catalysts. However, the (2+2) and (4+2) cycloadditions have different predilections for axial and central chirality combinations.

Expanding the Horizon of Bio-Inspired Catalyst Design with Tactical Incorporation of Drug Molecules.

The development of potent H2 production catalysts is a key aspect in our journey toward the establishment of a sustainable carbon-neutral power infrastructure. Hydrogenase enzymes provide the blueprint for designing efficient catalysts by the rational combination of central metal core and protein scaffold-based outer coordination sphere (OCS). Traditionally, a biomimetic catalyst is crafted by including natural amino acids as OCS features around a synthetic metal motif to functionally imitate the metalloenzyme activity. Here, we have pursued an unconventional approach and implanted two distinct drug molecules (isoniazid and nicotine hydrazide) at the axial position of a cobalt core to create a new genre of synthetic catalysts. The resultant cobalt complexes are active for both electrocatalytic and photocatalytic H2 production in near-neutral water, where they significantly enhance the catalytic performance of the unfunctionalized parent cobalt complex. The drug molecules showcased a dual effect as they influence the catalytic HER by improving the surrounding proton relay along and exerting subtle electronic effects. The isoniazid-ligated catalyst C1 outperformed the nicotine hydrazide-bound complex C2, as it produced H2 from water (pH 6.0) at a rate of 3960 s-1 while exhibiting Faradaic efficiency of about 90 %. This strategy opens up newer avenues of bio-inspired catalyst design beyond amino acid-based OCS features.

Recent Advances of VOCs Catalytic Oxidation over Spinel Oxides: Catalyst Design and Reaction Mechanism.

Volatile organic compounds (VOCs) harm the environment and human health and have been of wide concern and purified efficiently by catalytic oxidation. Spinel oxides, mainly composed of transition metal elements with low price and extensive sources, have been widely investigated as efficient and stable catalysts for VOCs oxidation due to their adjustable element composition, flexible structure, and high thermal/chemical stability. However, it is necessary to dissect the design of the spinel in a targeted way to satisfy the removal of different types of VOCs. This article systematically summarizes the recent advances regarding the application of spinel oxides for VOCs catalytic oxidation. Specifically, the design strategies of spinel oxides were first introduced to clarify their effect on the structure and properties of the catalyst. Then the reaction mechanism and degradation pathway of different kinds of VOCs on the spinel oxides were in detail summarized, and the characteristic requirements of the spinel oxides for various VOCs purification were analyzed. Furthermore, the practice applications were also discussed. Finally, the prospects were proposed to guide the rational design of spinel-based catalysts for VOCs purification and intensify the understanding of reaction mechanisms.

Recent Developments and Trends in Asymmetric Organocatalysis.

Asymmetric organocatalysis has experienced a long and spectacular way since the early reports over a century ago by von Liebig, Knoevenagel and Bredig, showing that small (chiral) organic molecules can catalyze (asymmetric) reactions. This was followed by impressive first highly enantioselective reports in the second half of the last century, until the hype initiated in 2000 by the milestone publications of MacMillan and List, which finally culminated in the 2021 Nobel Prize in Chemistry. This short Perspective aims at providing a brief introduction to the field by first looking on the historical development and the more classical methods and concepts, followed by discussing selected advanced recent examples that opened new directions and diversity within this still growing field.

Towards Machine Learning in Heterogeneous Catalysis-A Case Study of 2,4-Dinitrotoluene Hydrogenation.

Utilization of multivariate data analysis in catalysis research has extraordinary importance. The aim of the MIRA21 (MIskolc RAnking 21) model is to characterize heterogeneous catalysts with bias-free quantifiable data from 15 different variables to standardize catalyst characterization and provide an easy tool to compare, rank, and classify catalysts. The present work introduces and mathematically validates the MIRA21 model by identifying fundamentals affecting catalyst comparison and provides support for catalyst design. Literature data of 2,4-dinitrotoluene hydrogenation catalysts for toluene diamine synthesis were analyzed by using the descriptor system of MIRA21. In this study, exploratory data analysis (EDA) has been used to understand the relationships between individual variables such as catalyst performance, reaction conditions, catalyst compositions, and sustainable parameters. The results will be applicable in catalyst design, and using machine learning tools will also be possible.

Quantitative Structure-Electrochemistry Relationship (QSER) Studies on Metal-Amino-Porphyrins for the Rational Design of CO2 Reduction Catalysts.

The quantitative structure-electrochemistry relationship (QSER) method was applied to a series of transition-metal-coordinated porphyrins to relate their structural properties to their electrochemical CO2 reduction activity. Since the reactions mainly occur within the core of the metalloporphyrin catalysts, the cluster model was used to calculate their structural and electronic properties using density functional theory with the M06L exchange-correlation functional. Three dependent variables were employed in this work: the Gibbs free energies of H*, C*OOH, and O*CHO. QSER, with the genetic algorithm combined with multiple linear regression (GA-MLR), was used to manipulate the mathematical models of all three Gibbs free energies. The obtained statistical values resulted in a good predictive ability (R2 value) greater than 0.945. Based on our QSER models, both the electronic properties (charges of the metal and porphyrin) and the structural properties (bond lengths between the metal center and the nitrogen atoms of the porphyrin) play a significant role in the three Gibbs free energies. This finding was further applied to estimate the CO2 reduction activities of the metal-monoamino-porphyrins, which will prove beneficial in further experimental developments.

Recent Advances in the Reverse Water-Gas Conversion Reaction.

The increase in carbon dioxide emissions has significantly impacted human society and the global environment. As carbon dioxide is the most abundant and cheap C1 resource, the conversion and utilization of carbon dioxide have received extensive attention from researchers. Among the many carbon dioxide conversion and utilization methods, the reverse water-gas conversion (RWGS) reaction is considered one of the most effective. This review discusses the research progress made in RWGS with various heterogeneous metal catalyst types, covering topics such as catalyst performance, thermodynamic analysis, kinetics and reaction mechanisms, and catalyst design and preparation, and suggests future research on RWGS heterogeneous catalysts.

Catalyst-Oriented Design Based on Elementary Reactions (CODER) for Triarylamine Synthesis.

Recently, the application of computational tools to the rational design of catalysts has received considerable attention, but progress has been limited by the reliance on databases and because mechanistic data have been almost neglected. Herein, we report a new strategy for catalyst design, designated catalyst-oriented design based on elementary reactions (CODER), which fully utilizes mechanistic data, combines the strengths of computational tools and researcher experience. CODER enabled the development of extremely efficient Pd catalysts for C-N coupling, which markedly improved the efficiency of the synthesis of widely used triarylamine optoelectronic materials by enhancing the turnover numbers (up to 340000) to 1-3 orders of magnitude towards literature values.

Carbon Deposit Analysis in Catalyst Deactivation, Regeneration, and Rejuvenation.

Hydrocarbon conversion catalysts suffer from deactivation by deposition or formation of carbon deposits. Carbon deposit formation is thermodynamically favored above 350 °C, even in some hydrogen-rich environments. We discuss four basic mechanisms: a carbenium-ion based mechanism taking place on acid sites of zeolites or bifunctional catalysts, a metal-induced formation of soft coke (i.e., oligomers of small olefins) on bifunctional catalysts, a radical-mediated mechanism in higher-temperature processes, and fast-growing carbon filament formation. Catalysts deactivate because carbon deposits block pores at different length scales, or directly block active sites. Some deactivated catalysts can be re-used, others can be regenerated or have to be discarded. Catalyst and process design can mitigate the effects of deactivation. New analytical tools allow for the direct observation (in some cases even under in situ or operando conditions) of the 3D-distribution of coke-type species as a function of catalyst structure and lifetime.

Advances in the Electrocatalytic Hydrogen Evolution Reaction by Metal Nanoclusters-based Materials.

With the development of renewable energy systems, clean hydrogen is burgeoning as an optimal alternative to fossil fuels, in which its application is promising to retarding the global energy and environmental crisis. The hydrogen evolution reaction (HER), capable of producing high-purity hydrogen rapidly in electrocatalytic water splitting, has received much attention. Abundant research about HER has been done, focusing on advanced electrocatalyst design with high efficiency and robust stability. As potential HER catalysts, metal nanoclusters (MNCs) have been studied extensively. They are composed of several to a hundred metal atoms, with sizes being comparable to the Fermi wavelength of electrons, that is, < 2.0 nm. Different from metal atoms/nanoparticles, they exhibit unique catalytic properties due to their quantum size effect and low-coordination environment. In this review, the activity-enhancing approaches of MNCs applied in HER electrocatalysis are mainly summarized. Furthermore, recent progress in MNCs classified with different stabilization strategies, that is, the freestanding MNCs, MNCs with organic, metal and carbon supports, are introduced. Finally, the current challenges and deficiencies of these MNCs for HER are prospected.

Theoretical Perspectives in Organocatalysis.

It is clear that the field of organocatalysis is continuously expanding during the last decades. With increasing computational capacity and new techniques, computational methods have provided a more economic approach to explore different chemical systems. This review offers a broad yet concise overview of current state-of-the-art studies that have employed novel strategies for catalyst design. The evolution of the all different theoretical approaches most commonly used within organocatalysis is discussed, from the traditional approach, manual-driven, to the most recent one, machine-driven.

Enhancement of Power-to-Gas via Multi-catalyst Reactors Tailoring Reaction Rate and Heat Exchange.

The Sabatier reaction is a key element of power-to-gas development. For this reason, even though the process is known since more than one century, the Sabatier reaction is currently the object of important research efforts towards the development of new catalysts for performance improvement. However, the industrial exploitation of the Sabatier reaction depends on the development of reactors that match the best catalyst with an appropriate heat management. For this reason, this paper develops a methodology for the contemporary optimization of the reactor concept and the catalysts. It is observed that the reactor can be divided into three sections with contrasting requirements. In the first section, the main requirement concerns the reach of the reaction activation conditions. Hence, an adequate match between catalyst and reactor is needed, for example with an appropriate pre-heater. Once the reaction is activated, a reaction hotspot is formed, so that the cooling becomes determining and the main requirement for the catalyst is the resistance to poisoning and sintering. In the last section of the reactor, the low temperature activity of the catalyst is determining, so that a high-performing catalyst is needed. This paper indicates a strategy for the rational design of this catalyst, based on mechanistic evidences.

Increasing the Number of Aluminum Atoms in T3 Sites of a Mordenite Zeolite by Low-Pressure SiCl4 Treatment to Catalyze Dimethyl Ether Carbonylation.

Controlling the location of aluminum atoms in a zeolite framework is critical for understanding structure-performance relationships of catalytic reaction systems and tailoring catalyst design. Herein, we report a strategy to preferentially relocate mordenite (MOR) framework Al atoms into the desired T3 sites by low-pressure SiCl4 treatment (LPST). High-field 27 Al NMR was used to identify the exact location of framework Al for the MOR samples. The results indicate that 73 % of the framework Al atoms were at the T3 sites after LPST under optimal conditions, which leads to controllably generating and intensifying active sites in MOR zeolite for the dimethyl ether (DME) carbonylation reaction with higher methyl acetate (MA) selectivity and much longer lifetime (25 times). Further research reveals that the Al relocation mechanism involves simultaneous extraction, migration, and reinsertion of Al atoms from and into the parent MOR framework. This unique method is potentially applicable to other zeolites to control Al location.