Chem Catalysis

Journal: Chem Catalysis

Publisher

Cell Press

ISSN

2667-1093

Show all metadata

Search Results

Publications 1 - 10 of 10

Advanced database mining of efficient haloalkane dehalogenases by sequence and structure bioinformatics and microfluidics
Vasina, Michal; Vanacek, Pavel; Hon, Jiri; et al. (2022)
Chem Catalysis
Next-generation sequencing doubles genomic databases every 2.5 years. The accumulation of sequence data provides a unique opportunity to identify interesting biocatalysts directly in the databases without tedious and time-consuming engineering. Herein, we present a pipeline integrating sequence and structural bioinformatics with microfluidic enzymology for bioprospecting of efficient and robust haloalkane dehalogenases. The bioinformatic part identified 2,905 putative dehalogenases and prioritized a “small-but-smart” set of 45 genes, yielding 40 active enzymes, 24 of which were biochemically characterized by microfluidic enzymology techniques. Combining microfluidics with modern global data analysis provided precious mechanistic insights related to the high catalytic efficiency of selected enzymes. Overall, we have doubled the dehalogenation “toolbox” characterized over three decades, yielding biocatalysts that surpass the efficiency of currently available wild-type and engineered enzymes. This pipeline is generally applicable to other enzyme families and can accelerate the identification of efficient biocatalysts for industrial use.
The role of metal nanostructure in ceria-supported catalysts for ammonia oxidation to nitrous oxide
Surin, Ivan; Yang, Qingxin; Krumeich, Frank; et al. (2025)
Chem Catalysis
Manganese (Mn) and chromium (Cr) catalysts supported on CeO2 enable direct ammonia oxidation to nitrous oxide, N2O, but the lack of synthesis-structure-performance relations hinders rational catalyst design. Herein, we generate a platform of CeO2-supported Mn and Cr catalysts, systematically varying the metal nanostructure from single atoms to nanoparticles, and the carrier redox properties, as confirmed by advanced characterization methods. Surface reducibility of CeO2 emerges as a general descriptor, controlling N2O productivity. Conversely, structure sensitivity is metal specific, with Mn-based systems achieving high N2O selectivity in single-atom and nanoparticle forms, while the selectivity of Cr-based systems is dependent on metal dispersion. In situ UV-visible (UV-vis), steady-state, and transient kinetic studies unveil the ability of redox-active MnOx to synergize with CeO2 and enhance oxygen transport for the reaction following a Mars-van Krevelen mechanism. This work provides fundamental insights into the role and function of each catalyst component and guidelines for the development of improved N2O synthesis catalysts.
Unlocking mixed oxides with unprecedented stoichiometries from heterometallic metal-organic frameworks for the catalytic hydrogenation of CO2
Castells-Gil, Javier; Ould-Chikh, Samy; Ramirez Galilea, Adrian; et al. (2021)
Chem Catalysis
Their complex surface chemistry and high oxygen lattice mobilities place mixed-metal oxides among the most important families of materials. Modulation of stoichiometry in mixed-metal oxides has been shown to be a very powerful tool for tuning optical and catalytic properties. However, accessing different stoichiometries is not always synthetically possible. Here, we show that the thermal decomposition of the recently reported metal-organic framework MUV-101(Fe, Ti) results in the formation of carbon-supported titanomaghemite nanoparticles with an unprecedented Fe/Ti ratio close to 2, not achievable by soft-chemistry routes. The resulting titanomaghemite phase displays outstanding catalytic activity for the production of CO from CO2 via the reverse water-gas shift (RWGS) reaction with CO selectivity values of ca. 100% and no signs of deactivation after several days on stream. Theoretical calculations suggest that the reaction proceeds through the formation of COOH∗ species, favoring in this way CO over other byproducts.
Electron paramagnetic resonance spectroscopy for the analysis of single-atom catalysts
Agrachev, Mikhail; Giulimondi, Vera; Surin, Ivan; et al. (2024)
Chem Catalysis
Single-atom catalysts (SACs) are an important material class, lying at the forefront of precision design for heterogeneous catalysis research. Despite extensive investigations of their structure and reactivity using state-of-the-art analytical tools, new approaches are sought to improve the understanding of their properties and catalytic behavior. This review highlights the often-overlooked potential of electron paramagnetic resonance (EPR) spectroscopy, which is exceptionally suited to studying isolated paramagnetic species. EPR provides valuable complementary insights into SACs, including metal oxidation state, dispersion degree, local coordination environment, and catalytically relevant features of support materials. To enhance the technique’s accessibility, we provide a tutorial on EPR, summarize significant findings to date, place them within a broader methodological framework for SAC applications, and identify key directions for future research.
Identifying selective catalysts in polypropylene hydrogenolysis by decoupling scission pathways
Jaydev, Shibashish D.; Usteri, Marc-Eduard; Martín, Antonio J.; et al. (2023)
Chem Catalysis
Practical catalytic processing of polypropylene waste into high-value liquid alkanes via hydrogenolysis demands minimizing methane formation. Methane can mostly originate from either undesired demethylation of branched chains or inappropriate reaction conditions leading to excessively deep backbone scission. To date, identification of catalysts promoting backbone scission has been precluded by insufficient mechanistic tools. This work introduces scission preference, the metric providing the ratio between backbone scission and demethylation events when hydrogenolysis predominates obtainable from routine product analysis. Clear mechanistic differences on representative supported ruthenium catalysts could thus be quantified, with computed values ranging from 0.3 (Ru/CeO2) to 1.1 (Ru/Al2O3) under applied conditions. Ru/TiO2 displayed the best activity-selectivity trade-off. This tool also revealed the dynamic nature of the cleavage mechanism as demethylation is progressively favored over time. Metal content and metal oxide basicity could also be correlated with scission preference, underscoring its parallel value for catalyst design studies.
Homogeneous and heterogeneous strategies of enantioselective hydrogenation: Critical evaluation and future prospects
Marianov, Aleksei N.; Jiang, Yijiao; Baiker, Alfons; et al. (2023)
Chem Catalysis
Asymmetric hydrogenation of unsaturated prochiral substrates is one of the most powerful tools for the creation of enantiopure products. This remarkable reaction could be driven by homogeneous or heterogeneous catalysts. The homogeneous systems, although usually non-reusable, offer well-defined active sites, numerous options for structural optimization, and excellent performance. In contrast, heterogeneous systems are generally less structurally uniform and sometimes require more complex synthesis. At the same time, heterogeneous catalysts are reusable, are simpler to separate, and provide access to continuous processes. There are multiple practical limitations affecting both homogeneous and heterogeneous reactions, such as substrate scope, stability, and compatibility of substrates with solvents. Besides the material discovery, engineering aspects such as overall safety of the system and its lifecycle must be considered. This critical review aims to provide an introductory discussion on the advantages, issues, and future developments one needs to consider upon entry into the field of enantioselective hydrogenation.
Defective zirconia promotes monometallic iron catalysts for higher alcohol synthesis
Ge, Yuzhen; Zou, Tangsheng; Martín Fernández, Antonio José; et al. (2024)
Chem Catalysis
Efforts spanning decades toward the implementation of direct synthesis of higher alcohols from syngas have been unfruitful. Progress is hindered by insufficient understanding derived from catalyst complexity, as the need for different functionalities usually requires combining various metals, promoters, and supports. We reveal that iron becomes a remarkable catalyst when promoted by zirconia. Iron with 10 mol% ZrO₂ achieves a space-time yield of 250 mgHA h⁻¹ gcat⁻¹ and 30% selectivity to higher alcohols at their optimized conditions, superior to reported monometallic Fe catalysts and comparable to state-of-the-art multimetallic materials. This catalyst, with an outstanding balance between performance and simplicity, was examined via operando X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Oxygen vacancy formation and healing in amorphous ZrO₂ clusters enhance H₂ and CO activation and Fe₅C₂ formation in contact with Fe₃O₄. Activity-composition correlations suggest this Fe₃O₄-Fe₅C₂ interface as the active phase. Promoted monometallic iron emerges as a promising platform for future generations of catalysts.
Toward reliable and accessible ammonia quantification in the electrocatalytic reduction of nitrogen
Martín Fernández, Antonio José; Veenstra, Florentine L.P.; Lüthi, James; et al. (2021)
Chem Catalysis
Nitrogen electroreduction may alleviate fossil energy requirements to produce fertilizers, but efficient catalysts must still be developed. The development of accurate and accessible ammonia quantification tools is key to accelerate this process. This article provides guidelines to optimize sensitivity of UV-vis spectroscopy and the ion-selective electrode for initial catalyst screening. However, confirmation of the catalytic origin of ammonia is only feasible through 1H-NMR, which is much less frequently applied largely due to the high expertise and expensive apparatuses needed. We introduce a protocol accessible to catalyst practitioners applicable to widely available 300 MHz NMR spectrometers. To this end, we adapted the WATERGATE suppression method to accomplish high signal-to-noise ratios even in non-deuterated samples. It was demonstrated for a relevant concentration of 1 ppm, enabling qualitative and quantitative analysis in 2 and 15 min, respectively. By making 1H-NMR quantification more accessible, this study facilitates the application of state-of-the-art catalytic assessments.
Accelerated exploration of heterogeneous CO₂ hydrogenation catalysts by Bayesian-optimized high-throughput and automated experimentation
Ramirez Galilea, Adrian; Lam, Erwin; Gutierrez, Daniel Pacheco; et al. (2024)
Chem Catalysis
A closed -loop data -driven approach was used to optimize catalyst compositions for the direct transformation of carbon dioxide (CO2) into methanol by combining Bayesian optimization (BO), automated synthesis, and high -throughput catalytic performance evaluation in fixedbed reactors. The BO algorithm optimized a four -objective function simultaneously considering 8 experimental variables. In 6 weeks, 144 catalysts over 6 generations were synthesized and tested with limited manual laboratory activity. Between the first and fifth catalyst generation, the average CO2 conversion and methanol formation rates have been multiplied by 5.7 and 12.6, respectively, while simultaneously dividing the methane production rate and cost by 3.2 and 6.3, respectively. The best catalyst of the study shows an optimized composition of 1.85 wt % Cu, 0.69 wt % Zn, and 0.05 wt % Ce supported on ZrO2. Notably, the same dataset could also be reused to optimize the process toward different objectives and enable the identification of other catalyst compositions.
Ketones as ideal photocatalysts for decarboxylative fluorination and a competition with C(sp3)-H fluorination
Zhang, Yu; Qian, Jiahui; Wang, Miao; et al. (2024)
Chem Catalysis
Fluorinated molecules are widely used in drug discovery and materials science. However, the efficient construction of a C(sp3)–F bond from diverse carboxylic acids with a promising low-cost photocatalyst to replace expensive metal catalysts remains a significant challenge. Herein, we present a cost-effective, metal-free, and highly efficient photocatalytic approach for the direct decarboxylative fluorination of aliphatic carboxylic acids and diacids via photoexcited aliphatic ketones. This reaction (milligram to gram scale) can be achieved in just a few minutes with low-power irradiation using a broad range of wavelengths, spanning from visible to ultraviolet light. Our investigation revealed that photoexcited ketones, commonly employed as hydrogen atom transfer (HAT) catalysts for various C(sp3)–H bond functionalizations, exhibit a distinct preference for single-electron transfer (SET) in the decarboxylation of aliphatic carboxylic acids when combined with Selectfluor and Na2HPO4.

Publications 1 - 10 of 10

Journal: Chem Catalysis

Abbreviation

Publisher

Journal Volumes

ISSN

Description

Filters

Search Results