Pub Date : 2024-06-24DOI: 10.1021/acscatal.4c01961
Long Cheng, Rong Wang, Wenzhe Si, Yanxi Deng, Junhua Li, Yue Peng
Cu-based catalysts leveraging Cu+/Cu0 active sites have emerged as pivotal for synthesizing essential hydrocarbons and alcohols in electrochemical CO2 reduction, such as ethylene and ethanol (C2 products). However, the dynamic reduction of Cu+ to Cu0 during electroreduction leads to site instability, resulting in diminished efficiency for CO2 conversion to C2 products. Herein, we introduced Si into CuO by the selective dissolution method, engendering Cu–O–Si units to stabilize the Cu+/Cu0 sites. The catalyst manifested good activity in CO2 electroreduction with an elevated Faradaic efficiency for C2 products reaching 81.9% at −100 mA/cm2. After ten cycles of electrochemical testing, the Cu+/Cu0 sites and performance exhibited no signs of degradation. The Si incorporation significantly improved the hybridization of O 2p and Cu 3d orbitals, thereby reinforcing the Cu–O bonds and stabilizing the Cu+/Cu0 sites, which was critical in promoting C–C coupling via decreasing the energy barriers for *OCCO formation and enhancing C2 product selection. The active Cu+ cations with unsaturated coordination contributed to the reaction stabilization, thereby improving the preservation of Cu2O metastable state.
{"title":"Enhancing CO2 Electroreduction Performance through Si-Doped CuO: Stabilization of Cu+/Cu0 Sites and Improved C2 Product Selectivity","authors":"Long Cheng, Rong Wang, Wenzhe Si, Yanxi Deng, Junhua Li, Yue Peng","doi":"10.1021/acscatal.4c01961","DOIUrl":"https://doi.org/10.1021/acscatal.4c01961","url":null,"abstract":"Cu-based catalysts leveraging Cu<sup>+</sup>/Cu<sup>0</sup> active sites have emerged as pivotal for synthesizing essential hydrocarbons and alcohols in electrochemical CO<sub>2</sub> reduction, such as ethylene and ethanol (C<sub>2</sub> products). However, the dynamic reduction of Cu<sup>+</sup> to Cu<sup>0</sup> during electroreduction leads to site instability, resulting in diminished efficiency for CO<sub>2</sub> conversion to C<sub>2</sub> products. Herein, we introduced Si into CuO by the selective dissolution method, engendering Cu–O–Si units to stabilize the Cu<sup>+</sup>/Cu<sup>0</sup> sites. The catalyst manifested good activity in CO<sub>2</sub> electroreduction with an elevated Faradaic efficiency for C<sub>2</sub> products reaching 81.9% at −100 mA/cm<sup>2</sup>. After ten cycles of electrochemical testing, the Cu<sup>+</sup>/Cu<sup>0</sup> sites and performance exhibited no signs of degradation. The Si incorporation significantly improved the hybridization of O 2p and Cu 3d orbitals, thereby reinforcing the Cu–O bonds and stabilizing the Cu<sup>+</sup>/Cu<sup>0</sup> sites, which was critical in promoting C–C coupling via decreasing the energy barriers for *OCCO formation and enhancing C<sub>2</sub> product selection. The active Cu<sup>+</sup> cations with unsaturated coordination contributed to the reaction stabilization, thereby improving the preservation of Cu<sub>2</sub>O metastable state.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141448820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Various decarbonylation reactions via oxidative addition of carbonyl compounds to metal catalysts can be applied to late-stage modification and have been actively studied to date; however, several inherent problems derived from the oxidative addition are difficult to solve, such as toxic CO production, deactivation of catalysts by CO adsorption, intolerance of some functional groups, or air-sensitivity of catalysts. In this context, formal decarbonylation, which eliminates CO as other compounds without involving oxidative addition, is attractive but hardly reported, especially using heterogeneous catalysts. Herein, formal decarbonylation of diaryl 1,2-diketones to afford monoketones using CeO2 as a reusable heterogeneous catalyst and O2 in the air as the terminal oxidant was developed, generating CO2 as the only byproduct. The results revealed that the reaction was enabled by the synergistic catalytic effect of the Lewis acid–base pairs and redox properties in CeO2.
通过将羰基化合物氧化加成到金属催化剂上的各种脱羰基反应可应用于后期改性，迄今为止，人们对这些反应进行了积极的研究；然而，氧化加成产生的一些固有问题难以解决，如有毒 CO 的产生、催化剂因吸附 CO 而失活、某些官能团的不耐受性或催化剂对空气的敏感性。在这种情况下，形式脱羰基反应（不涉及氧化加成就能像消除其他化合物一样消除 CO）很有吸引力，但鲜有报道，尤其是使用异质催化剂。本文以 CeO2 为可重复使用的异质催化剂，以空气中的 O2 为末端氧化剂，对 1,2-二酮类二芳基化合物进行了形式脱羰基反应，生成了单酮类化合物，唯一的副产物是 CO2。研究结果表明，CeO2 中路易斯酸碱对和氧化还原特性的协同催化作用使反应得以进行。
{"title":"Formal Decarbonylation of 1,2-Diketones Enabled by Synergistic Catalysis of Lewis Acid–Base Pairs and Redox Properties in CeO2","authors":"Takehiro Matsuyama, Takafumi Yatabe, Kazuya Yamaguchi","doi":"10.1021/acscatal.4c02493","DOIUrl":"https://doi.org/10.1021/acscatal.4c02493","url":null,"abstract":"Various decarbonylation reactions via oxidative addition of carbonyl compounds to metal catalysts can be applied to late-stage modification and have been actively studied to date; however, several inherent problems derived from the oxidative addition are difficult to solve, such as toxic CO production, deactivation of catalysts by CO adsorption, intolerance of some functional groups, or air-sensitivity of catalysts. In this context, formal decarbonylation, which eliminates CO as other compounds without involving oxidative addition, is attractive but hardly reported, especially using heterogeneous catalysts. Herein, formal decarbonylation of diaryl 1,2-diketones to afford monoketones using CeO<sub>2</sub> as a reusable heterogeneous catalyst and O<sub>2</sub> in the air as the terminal oxidant was developed, generating CO<sub>2</sub> as the only byproduct. The results revealed that the reaction was enabled by the synergistic catalytic effect of the Lewis acid–base pairs and redox properties in CeO<sub>2</sub>.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141435911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1021/acscatal.4c01566
Man Guo, Nanchen Dongfang, Marcella Iannuzzi, Jeroen Anton van Bokhoven, Luca Artiglia
The epoxidation of ethylene stands as one of the most important industrial catalytic reactions, and silver-based catalysts show superior activity and selectivity. Oxygen is activated on the surface of silver during the reaction and exerts a substantial impact on product selectivity. Notably, the oxygen species residing in the topmost atomic layers profoundly influence the reactivity of a catalyst. However, their characterization under in situ reaction conditions remains a huge challenge, and specific structures have not been identified yet. In this study, we employ in situ X-ray photoelectron spectroscopy and density functional theory calculations to determine the oxygen species formed at the topmost atomic layers of a silver foil and to assign them a structure. Three different groups of oxygen species activated on silver are identified: (i) surface lattice oxygen and two oxygen species originating from associatively adsorbed dioxygen and (ii) top and (iii) subsurface oxygen. Transient in situ photoelectron spectroscopy experiments are carried out to reveal the dynamic evolution and thus reactivity of the different oxygen species under ethylene epoxidation reaction environments. The top oxygen atom from the adsorbed associated dioxygen is the most active. Meanwhile, a frequency-selective data analysis method, developed to process time-resolved data, provides insights into the evolving trends of peak intensities for different oxygen species. The versatility of this method suggests its potential application in future time-resolved characterization studies.
乙烯的环氧化反应是最重要的工业催化反应之一，银基催化剂显示出卓越的活性和选择性。在反应过程中，氧会在银表面被激活，并对产物的选择性产生重大影响。值得注意的是，停留在最顶层原子层的氧物种会对催化剂的反应活性产生深远影响。然而，在原位反应条件下对它们进行表征仍然是一个巨大的挑战，而且尚未确定其具体结构。在本研究中，我们利用原位 X 射线光电子能谱和密度泛函理论计算，确定了在银箔最顶层原子层形成的氧物种，并为它们分配了结构。我们确定了在银上活化的三组不同的氧物种：(i) 表面晶格氧和源自关联吸附二氧的两种氧物种；(ii) 顶部氧和 (iii) 次表层氧。瞬态原位光电子能谱实验揭示了不同氧物种在乙烯环氧化反应环境下的动态演变和反应活性。吸附的伴生二氧的顶部氧原子最为活跃。与此同时，为处理时间分辨数据而开发的频率选择性数据分析方法可帮助人们深入了解不同氧物种峰强度的演变趋势。这种方法的多功能性表明它有可能应用于未来的时间分辨表征研究。
{"title":"Structure and Reactivity of Active Oxygen Species on Silver Surfaces for Ethylene Epoxidation","authors":"Man Guo, Nanchen Dongfang, Marcella Iannuzzi, Jeroen Anton van Bokhoven, Luca Artiglia","doi":"10.1021/acscatal.4c01566","DOIUrl":"https://doi.org/10.1021/acscatal.4c01566","url":null,"abstract":"The epoxidation of ethylene stands as one of the most important industrial catalytic reactions, and silver-based catalysts show superior activity and selectivity. Oxygen is activated on the surface of silver during the reaction and exerts a substantial impact on product selectivity. Notably, the oxygen species residing in the topmost atomic layers profoundly influence the reactivity of a catalyst. However, their characterization under in situ reaction conditions remains a huge challenge, and specific structures have not been identified yet. In this study, we employ in situ X-ray photoelectron spectroscopy and density functional theory calculations to determine the oxygen species formed at the topmost atomic layers of a silver foil and to assign them a structure. Three different groups of oxygen species activated on silver are identified: (i) surface lattice oxygen and two oxygen species originating from associatively adsorbed dioxygen and (ii) top and (iii) subsurface oxygen. Transient in situ photoelectron spectroscopy experiments are carried out to reveal the dynamic evolution and thus reactivity of the different oxygen species under ethylene epoxidation reaction environments. The top oxygen atom from the adsorbed associated dioxygen is the most active. Meanwhile, a frequency-selective data analysis method, developed to process time-resolved data, provides insights into the evolving trends of peak intensities for different oxygen species. The versatility of this method suggests its potential application in future time-resolved characterization studies.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The conversion of H2S to high-value-added products is appealing for alleviating environmental pollution and realizing resource utilization. Herein, we report the reduction of nitrobenzene to aniline using waste H2S as a “hydrogen donor” over the catalyst of FeCeO2−δ with abundant oxygen vacancies (Ov), especially an asymmetric oxygen vacancy (ASOv). The electron-rich nature of the ASOv sites facilitates electron transfer to the electron-deficient nitro group, promoting the adsorption and activation of Ph–NO2 through the elongation and cleavage of the N–O bond. Benefiting from the formation of abundant ASOv sites, the resulting FeCeO2−δ achieves an impressive 85.6% Ph–NO2 conversion and 81.9% Ph–NH2 selectivity at 1.5 MPa and 90 °C, which surpasses that of pure CeO2 with flower and rod morphologies. In situ FT-IR measurements combined with density functional theory calculations have elucidated a plausible reaction mechanism and a rate-limiting step in the hydrogenation of Ph–NO2 by H2S.
{"title":"Asymmetric Oxygen Vacancy-Promoted Synthesis of Aminoarenes from Nitroarenes Using Waste H2S as a “Hydrogen Donor”","authors":"Xiaohai Zheng, Bang Li, Rui Huang, Weiping Jiang, Lijuan Shen, Ganchang Lei, Shiping Wang, Yingying Zhan, Lilong Jiang","doi":"10.1021/acscatal.4c02478","DOIUrl":"https://doi.org/10.1021/acscatal.4c02478","url":null,"abstract":"The conversion of H<sub>2</sub>S to high-value-added products is appealing for alleviating environmental pollution and realizing resource utilization. Herein, we report the reduction of nitrobenzene to aniline using waste H<sub>2</sub>S as a “hydrogen donor” over the catalyst of FeCeO<sub>2−δ</sub> with abundant oxygen vacancies (Ov), especially an asymmetric oxygen vacancy (ASOv). The electron-rich nature of the ASOv sites facilitates electron transfer to the electron-deficient nitro group, promoting the adsorption and activation of Ph–NO<sub>2</sub> through the elongation and cleavage of the N–O bond. Benefiting from the formation of abundant ASOv sites, the resulting FeCeO<sub>2−δ</sub> achieves an impressive 85.6% Ph–NO<sub>2</sub> conversion and 81.9% Ph–NH<sub>2</sub> selectivity at 1.5 MPa and 90 °C, which surpasses that of pure CeO<sub>2</sub> with flower and rod morphologies. In situ FT-IR measurements combined with density functional theory calculations have elucidated a plausible reaction mechanism and a rate-limiting step in the hydrogenation of Ph–NO<sub>2</sub> by H<sub>2</sub>S.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1021/acscatal.4c02813
Daniyal Kiani, Israel E. Wachs
Understanding reaction kinetics is crucial for designing and applying heterogeneous catalytic processes in chemical and energy conversion. Here, we revisit the Langmuir–Hinshelwood (L-H) kinetic model for bimolecular surface reactions, originally formulated for metal catalysts, assuming immobile adsorbates on neighboring pair sites, with the rate varying linearly with the density of surface sites (sites per unit area); r ∝ [*]o1. Supported metal oxide catalysts, however, offer systematic control over [*]o through variation of the active two-dimensional metal oxide loading in the submonolayer region. Various reactions catalyzed by supported metal oxides are analyzed, such as supported VOx catalysts, including methanol oxidation, oxidative dehydrogenation of propane and ethane, SO2 oxidation to SO3, propene oxidation to acrolein, n-butane oxidation to maleic anhydride, and selective catalytic reduction of nitric oxide with ammonia. The analysis reveals diverse dependencies of reaction rate on [*]o for these surface reactions, with r ∝ [*]on, where n equals 1 for reactions with a unimolecular rate-determining step and 2 for those with a bimolecular rate-limiting step or exchange of more than 2 electrons. We propose refraining from a priori assumptions about the nature and density of surface sites or adsorbate behavior, advocating instead for data-driven elucidation of kinetics based on the density of surface sites, adsorbate coverage, etc. Additionally, recent studies on catalytic surface mechanisms have shed light on nonadjacent catalytic sites catalyzing surface reactions in contrast to the traditional requirement of adjacent/pair sites. These findings underscore the need for a more nuanced approach in modeling heterogeneous catalysis, especially supported metal oxide catalysts, encouraging reliance on experimental data over idealized assumptions that are often difficult to justify.
{"title":"The Conundrum of “Pair Sites” in Langmuir–Hinshelwood Reaction Kinetics in Heterogeneous Catalysis","authors":"Daniyal Kiani, Israel E. Wachs","doi":"10.1021/acscatal.4c02813","DOIUrl":"https://doi.org/10.1021/acscatal.4c02813","url":null,"abstract":"Understanding reaction kinetics is crucial for designing and applying heterogeneous catalytic processes in chemical and energy conversion. Here, we revisit the Langmuir–Hinshelwood (L-H) kinetic model for bimolecular surface reactions, originally formulated for metal catalysts, assuming immobile adsorbates on neighboring pair sites, with the rate varying linearly with the density of surface sites (sites per unit area); <i>r</i> ∝ [*]<sub>o</sub><sup>1</sup>. Supported metal oxide catalysts, however, offer systematic control over [*]<sub>o</sub> through variation of the active two-dimensional metal oxide loading in the submonolayer region. Various reactions catalyzed by supported metal oxides are analyzed, such as supported VO<sub><i>x</i></sub> catalysts, including methanol oxidation, oxidative dehydrogenation of propane and ethane, SO<sub>2</sub> oxidation to SO<sub>3</sub>, propene oxidation to acrolein, <i>n</i>-butane oxidation to maleic anhydride, and selective catalytic reduction of nitric oxide with ammonia. The analysis reveals diverse dependencies of reaction rate on [*]<sub>o</sub> for these surface reactions, with <i>r</i> ∝ [*]<sub>o</sub><sup><i>n</i></sup>, where <i>n</i> equals 1 for reactions with a unimolecular rate-determining step and 2 for those with a bimolecular rate-limiting step or exchange of more than 2 electrons. We propose refraining from a priori assumptions about the nature and density of surface sites or adsorbate behavior, advocating instead for data-driven elucidation of kinetics based on the density of surface sites, adsorbate coverage, etc. Additionally, recent studies on catalytic surface mechanisms have shed light on nonadjacent catalytic sites catalyzing surface reactions in contrast to the traditional requirement of adjacent/pair sites. These findings underscore the need for a more nuanced approach in modeling heterogeneous catalysis, especially supported metal oxide catalysts, encouraging reliance on experimental data over idealized assumptions that are often difficult to justify.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1021/acscatal.4c01636
Lei Li, Huanhuan Liu, Chao Cheng, Xinyan Dai, Fang Chen, Jiqiang Ning, Wentao Wang, Yong Hu
Precisely engineering point defects holds promise for the development of state-of-the-art photocatalysts for CO2 conversion. This study demonstrates the controllable creation of nitrogen vacancies (VNs) in the centers of heptazine rings of graphitic carbon nitrides (g-C3N4) via a photochemical-assisted nitrogen etching strategy. Spectroscopic analyses and theoretical simulations elucidate the photochemical process to hydrogenate the nitrogen situated at the center of the g-C3N4 heptazine ring and then release an ammonia molecule, accompanied by the photooxidation of the sacrificial agents. The catalyst with an optimal VNs concentration achieves a CO generation rate of 35.2 μmol g–1 h–1 with nearly 100% selectivity, comparable to the performance of the reported g-C3N4 materials. The remarkably improved photoactivity is due to the adjustments of the electronic structures and the midgap states of g-C3N4 by the delocalized π electron cloud created in the 12-membered ring surrounding the VN, which maximizes the light-harvesting efficiencies and suppresses the recombination of photogenerated electrons and holes. The VNs also activates the neighboring catalytic carbon centers to reduce the energy barrier for CO2 reduction. This work provides a good design concept to regulate catalytic activity by engineering point defects.
{"title":"Photochemical Tuning of Tricoordinated Nitrogen Deficiency in Carbon Nitride to Create Delocalized π Electron Clouds for Efficient CO2 Photoreduction","authors":"Lei Li, Huanhuan Liu, Chao Cheng, Xinyan Dai, Fang Chen, Jiqiang Ning, Wentao Wang, Yong Hu","doi":"10.1021/acscatal.4c01636","DOIUrl":"https://doi.org/10.1021/acscatal.4c01636","url":null,"abstract":"Precisely engineering point defects holds promise for the development of state-of-the-art photocatalysts for CO<sub>2</sub> conversion. This study demonstrates the controllable creation of nitrogen vacancies (<i>V</i><sub>Ns</sub>) in the centers of heptazine rings of graphitic carbon nitrides (g-C<sub>3</sub>N<sub>4</sub>) via a photochemical-assisted nitrogen etching strategy. Spectroscopic analyses and theoretical simulations elucidate the photochemical process to hydrogenate the nitrogen situated at the center of the g-C<sub>3</sub>N<sub>4</sub> heptazine ring and then release an ammonia molecule, accompanied by the photooxidation of the sacrificial agents. The catalyst with an optimal <i>V</i><sub>Ns</sub> concentration achieves a CO generation rate of 35.2 μmol g<sup>–1</sup> h<sup>–1</sup> with nearly 100% selectivity, comparable to the performance of the reported g-C<sub>3</sub>N<sub>4</sub> materials. The remarkably improved photoactivity is due to the adjustments of the electronic structures and the midgap states of g-C<sub>3</sub>N<sub>4</sub> by the delocalized π electron cloud created in the 12-membered ring surrounding the <i>V</i><sub>N</sub>, which maximizes the light-harvesting efficiencies and suppresses the recombination of photogenerated electrons and holes. The <i>V</i><sub>Ns</sub> also activates the neighboring catalytic carbon centers to reduce the energy barrier for CO<sub>2</sub> reduction. This work provides a good design concept to regulate catalytic activity by engineering point defects.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141436101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1021/acscatal.4c02747
Daniel J. DiRocco, Pronay Roy, Anushree Mondal, Prathamesh M. Datar, E. Neil G. Marsh
UbiD-like (de)carboxylase enzymes employ prenylated-FMN (prFMN) as a cofactor to catalyze (de)carboxylation reactions on otherwise unreactive aromatic rings and conjugated double bonds. UbiD-like enzymes are attractive for biocatalysis applications but are often difficult to obtain as active holoenzymes. Phenazine-1-carboxylic acid decarboxylase (PhdA) is one such case: even when coexpressed with its cognate prenylated-FMN synthase (PhdB), PhdA is largely obtained as inactive apoenzyme. Here, we show that a third protein, PhdC, encoded in the same operon, functions as maturase to catalyze the oxidation of reduced prFMN to the catalytically active form. Coexpression in E. coli of PhdA, PhdB, and PhdC allowed highly active holo-PhdA to be purified. Using purified proteins, we show that PhdC uses molecular oxygen to oxidize the prFMN semiquinone radical, formed by spontaneous air oxidation, to the active cofactor. Formation of the prFMN semiquinone radical by reaction with oxygen occurs nonenzymatically with k2app ∼ 6500 M–1 s–1 while the second, PhdC-catalyzed step to form fully oxidized prFMN occurs with kapp ∼ 0.35 min–1. In vitro reconstitution of apo-PhdA with prFMN oxidized by PhdC gives fully active holo-PhdA. PhdC also facilitated the installation of prFMN in furan-1,4-dicarboxylate decarboxylase, HmfF, suggesting that this enzyme may have general utility in the production of active holo-UbiD-like enzymes.
{"title":"An Enzyme Catalyzing the Oxidative Maturation of Reduced Prenylated-FMN to Form the Active Coenzyme","authors":"Daniel J. DiRocco, Pronay Roy, Anushree Mondal, Prathamesh M. Datar, E. Neil G. Marsh","doi":"10.1021/acscatal.4c02747","DOIUrl":"https://doi.org/10.1021/acscatal.4c02747","url":null,"abstract":"UbiD-like (de)carboxylase enzymes employ prenylated-FMN (prFMN) as a cofactor to catalyze (de)carboxylation reactions on otherwise unreactive aromatic rings and conjugated double bonds. UbiD-like enzymes are attractive for biocatalysis applications but are often difficult to obtain as active holoenzymes. Phenazine-1-carboxylic acid decarboxylase (PhdA) is one such case: even when coexpressed with its cognate prenylated-FMN synthase (PhdB), PhdA is largely obtained as inactive apoenzyme. Here, we show that a third protein, PhdC, encoded in the same operon, functions as maturase to catalyze the oxidation of reduced prFMN to the catalytically active form. Coexpression in <i>E. coli</i> of PhdA, PhdB, and PhdC allowed highly active holo-PhdA to be purified. Using purified proteins, we show that PhdC uses molecular oxygen to oxidize the prFMN semiquinone radical, formed by spontaneous air oxidation, to the active cofactor. Formation of the prFMN semiquinone radical by reaction with oxygen occurs nonenzymatically with <i>k</i><sub>2app</sub> ∼ 6500 M<sup>–1</sup> s<sup>–1</sup> while the second, PhdC-catalyzed step to form fully oxidized prFMN occurs with <i>k</i><sub>app</sub> ∼ 0.35 min<sup>–1</sup>. <i>In vitro</i> reconstitution of apo-PhdA with prFMN oxidized by PhdC gives fully active holo-PhdA. PhdC also facilitated the installation of prFMN in furan-1,4-dicarboxylate decarboxylase, HmfF, suggesting that this enzyme may have general utility in the production of active holo-UbiD-like enzymes.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1021/acscatal.4c01708
Wen-Ting Niu, Wanghui Zhao, Kai-Wen Feng, Fu-Jia Tang, Tao Wang, Kaixuan Wang, Shaohua Shen, Yang Li
Efficient hydrogen (H2) production from renewable resources, such as biomass, one of the largest renewable resources on the earth, instead of fossil resources, is highly desirable. Making it via HCO2H as an intermediate for H2 production from biomass both facilitates efficient H2 production and can avoid the issues of H2 storage. Herein, we report efficient H2 production from raw biomass-based formic acid (HCO2H) by a noble-metal-free catalysis system under mild conditions, enabled by cooperation of CdS/ZnS-S2– quantum dots photocatalysts with weak formaldehyde (HCHO) adsorption and in situ generated Ni0, resulting in H2 with a 94% yield in 3.5 h, with a 99.7% selectivity and a 537 ± 14 mol mg–1 h–1 average rate at 50 °C under visible-light irradiation. This study should promote the exploration of catalytic systems for streamlined H2 production from renewable biomass for practical application.
{"title":"Efficient H2 Production from Biomass-Based HCO2H by Cooperation of Quantum Dots Photocatalysts with Weak HCHO Adsorption and In Situ Generated Ni0","authors":"Wen-Ting Niu, Wanghui Zhao, Kai-Wen Feng, Fu-Jia Tang, Tao Wang, Kaixuan Wang, Shaohua Shen, Yang Li","doi":"10.1021/acscatal.4c01708","DOIUrl":"https://doi.org/10.1021/acscatal.4c01708","url":null,"abstract":"Efficient hydrogen (H<sub>2</sub>) production from renewable resources, such as biomass, one of the largest renewable resources on the earth, instead of fossil resources, is highly desirable. Making it via HCO<sub>2</sub>H as an intermediate for H<sub>2</sub> production from biomass both facilitates efficient H<sub>2</sub> production and can avoid the issues of H<sub>2</sub> storage. Herein, we report efficient H<sub>2</sub> production from raw biomass-based formic acid (HCO<sub>2</sub>H) by a noble-metal-free catalysis system under mild conditions, enabled by cooperation of CdS/ZnS-S<sup>2–</sup> quantum dots photocatalysts with weak formaldehyde (HCHO) adsorption and in situ generated Ni<sup>0</sup>, resulting in H<sub>2</sub> with a 94% yield in 3.5 h, with a 99.7% selectivity and a 537 ± 14 mol mg<sup>–1</sup> h<sup>–1</sup> average rate at 50 °C under visible-light irradiation. This study should promote the exploration of catalytic systems for streamlined H<sub>2</sub> production from renewable biomass for practical application.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141436104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Controlling the location and microenvironment of active centers in the zeolite framework is critical for understanding the in-depth structure–performance relationships of catalytic systems and constructing highly efficient catalysts. Herein, we have developed an MOR-type titanosilicate (denoted as 6M-Ti-M360) with an extremely low framework Ti content (Si/Ti = 300), exhibiting not only ultrahigh catalyst weight-based conversion (81%) but also a record-breaking turnover number (TON = 5845) per Ti site in batchwise ammoximation of cyclohexanone. Its highly isolated and active Ti species took the specific position of defective T3 sites within the eight-member ring side pockets of the MOR topology, evidenced by molecular dimension-dependent shape-selective experiments and theoretical evaluation of the catalytic activation ability of the different crystallographic Ti sites at the molecular level. Despite an extremely low Ti content but with the most active Ti on the defective T3 sites, the 6M-Ti-M360 catalyst maintained the cyclohexanone conversion and cyclohexanone oxime selectivity both as high as 99% for a long lifetime (314 h) in a continuous slurry bed reactor, capable of producing 1100 kg of oxime per gram of Ti. The clarification of the location and local microenvironment of Ti active sites may provide new insights into the exploration and construction of highly active sites in zeolitic catalysts.
控制沸石骨架中活性中心的位置和微环境对于深入理解催化体系的结构-性能关系和构建高效催化剂至关重要。在此，我们开发了一种框架 Ti 含量极低（Si/Ti = 300）的 MOR 型钛硅酸盐（记为 6M-Ti-M360），在批量氨基化环己酮的过程中，不仅表现出超高的催化剂重量转化率（81%），而且每个 Ti 位点的周转次数（TON = 5845）也打破了记录。通过分子维度依赖性形状选择实验以及对不同晶体学 Ti 位点在分子水平上的催化活化能力的理论评估，证明了其高度分离和活性 Ti 物种在 MOR 拓扑结构的八元环侧袋中占据了有缺陷的 T3 位点的特定位置。尽管 6M-Ti-M360 催化剂的 Ti 含量极低，但在有缺陷的 T3 位点上的 Ti 活性最高，因此在连续浆料床反应器中，环己酮转化率和环己酮肟选择性在较长的使用寿命（314 小时）内均保持在 99% 以上，每克 Ti 可生产 1100 公斤肟。澄清钛活性位点的位置和局部微环境可为探索和构建沸石催化剂中的高活性位点提供新的见解。
{"title":"MOR-Type Titanosilicate with Specific Ti Location in Defective T3 Sites for Efficient Cyclohexanone Ammoximation","authors":"Zhipeng Wan, Jingyi Tan, Wei Chen, Longkang Zhang, Xianchen Gong, Chengwei Zhai, Hao Xu, Anming Zheng, Peng Wu","doi":"10.1021/acscatal.4c01914","DOIUrl":"https://doi.org/10.1021/acscatal.4c01914","url":null,"abstract":"Controlling the location and microenvironment of active centers in the zeolite framework is critical for understanding the in-depth structure–performance relationships of catalytic systems and constructing highly efficient catalysts. Herein, we have developed an <b>MOR</b>-type titanosilicate (denoted as 6M-Ti-M360) with an extremely low framework Ti content (Si/Ti = 300), exhibiting not only ultrahigh catalyst weight-based conversion (81%) but also a record-breaking turnover number (TON = 5845) per Ti site in batchwise ammoximation of cyclohexanone. Its highly isolated and active Ti species took the specific position of defective T3 sites within the eight-member ring side pockets of the <b>MOR</b> topology, evidenced by molecular dimension-dependent shape-selective experiments and theoretical evaluation of the catalytic activation ability of the different crystallographic Ti sites at the molecular level. Despite an extremely low Ti content but with the most active Ti on the defective T3 sites, the 6M-Ti-M360 catalyst maintained the cyclohexanone conversion and cyclohexanone oxime selectivity both as high as 99% for a long lifetime (314 h) in a continuous slurry bed reactor, capable of producing 1100 kg of oxime per gram of Ti. The clarification of the location and local microenvironment of Ti active sites may provide new insights into the exploration and construction of highly active sites in zeolitic catalysts.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141436097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-20DOI: 10.1021/acscatal.4c01448
Aditya Prajapati, Nitish Govindarajan, Wenyu Sun, Jiayi Huang, Hossein Bemana, Jeremy T. Feaster, Sneha A. Akhade, Nikolay Kornienko, Christopher Hahn
The electrochemical oxidation of alcohols is being explored as a favorable substitute for the oxygen evolution reaction owing to its capability to generate high-value products and lower overpotentials. Herein, we present a systematic investigation into the electrochemical oxidation of 5-hydroxymethylfurfural (HMF), a model biomass platform chemical, on a thin-film nickel catalyst, aiming to investigate the underlying reaction mechanism and shed light on the role of the catalyst’s microenvironment and phase on activity and product selectivity. Utilizing a combined experimental and computational approach, we demonstrate that NiOOH is the active phase for HMF oxidation. Additionally, we find a substantial impact of the electrochemical environment, particularly the electrolyte pH, on the reaction. Under highly alkaline conditions (pH = 13), higher activity for HMF oxidation is observed, accompanied by an increased selectivity toward 2,5-furandicarboxylic acid (FDCA) production. Conversely, a less alkaline environment (pH = 11) results in diminished HMF oxidation activity and a higher preference for the partial oxidation product 2,5-diformylfuran (DFF). Mechanistic insights from DFT studies reveal that geminal diols that are present under highly alkaline conditions undergo hydride transfer via HMFCA, while a shift to an alkoxide route occurs at a lower pH, favoring the DFF pathway. Hydride transfer energetics are also strongly affected by the surface Ni oxidation state. This integrated approach, bridging experimental and computational insights, provides a general framework for investigating the electrochemical oxidation of aldehydes and alcohols, thereby advancing rational design strategies in electrocatalysts for alcohol electro-oxidation reactions.
{"title":"Mechanistic Insights into the Electrochemical Oxidation of 5-Hydroxymethylfurfural on a Thin-Film Ni Anode","authors":"Aditya Prajapati, Nitish Govindarajan, Wenyu Sun, Jiayi Huang, Hossein Bemana, Jeremy T. Feaster, Sneha A. Akhade, Nikolay Kornienko, Christopher Hahn","doi":"10.1021/acscatal.4c01448","DOIUrl":"https://doi.org/10.1021/acscatal.4c01448","url":null,"abstract":"The electrochemical oxidation of alcohols is being explored as a favorable substitute for the oxygen evolution reaction owing to its capability to generate high-value products and lower overpotentials. Herein, we present a systematic investigation into the electrochemical oxidation of 5-hydroxymethylfurfural (HMF), a model biomass platform chemical, on a thin-film nickel catalyst, aiming to investigate the underlying reaction mechanism and shed light on the role of the catalyst’s microenvironment and phase on activity and product selectivity. Utilizing a combined experimental and computational approach, we demonstrate that NiOOH is the active phase for HMF oxidation. Additionally, we find a substantial impact of the electrochemical environment, particularly the electrolyte pH, on the reaction. Under highly alkaline conditions (pH = 13), higher activity for HMF oxidation is observed, accompanied by an increased selectivity toward 2,5-furandicarboxylic acid (FDCA) production. Conversely, a less alkaline environment (pH = 11) results in diminished HMF oxidation activity and a higher preference for the partial oxidation product 2,5-diformylfuran (DFF). Mechanistic insights from DFT studies reveal that geminal diols that are present under highly alkaline conditions undergo hydride transfer via HMFCA, while a shift to an alkoxide route occurs at a lower pH, favoring the DFF pathway. Hydride transfer energetics are also strongly affected by the surface Ni oxidation state. This integrated approach, bridging experimental and computational insights, provides a general framework for investigating the electrochemical oxidation of aldehydes and alcohols, thereby advancing rational design strategies in electrocatalysts for alcohol electro-oxidation reactions.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":12.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：