Engineering the electronic structure and microenvironments of active sites is an effective strategy to enhance the oxygen evolution reaction (OER) kinetics. Meanwhile, most OER materials act only as precatalysts; therefore, understanding and modulation of restructuring kinetics is crucial for developing efficient OER active sites. Herein, a dopant-tuned restructuring kinetic for the generation of heterophase-confined metal-nonmetal diatomic sites has been achieved. Both operando spectra and theoretical evidence show that Zr dopants tune in situ restructuring kinetics and induce charge transfer between Ni and Se to generate Ni–Se diatomic sites that coordinate dynamically with oxygenated intermediates and reduce energy barriers significantly. Consequently, the dense Ni–Se diatomic sites display an overpotential of 224 mV vs reversible hydrogen electrode at 10 mAcm–2 and stable operation over 500 h in alkaline conditions, one of the best performances among reported selenide-derived OER catalysts. Our results enable an in-depth understanding of dynamically restructured diatomic sites beyond the conventional single-metal sites and expand the strategies for engineering atomic/molecular-level active sites.
{"title":"Dopant-Tuned Restructuring Kinetic for the Formation of Heterophase-Confined Metal-Nonmetal Diatomic Sites for Efficient Oxygen Evolution Reaction","authors":"Xinyi Li, Feiyan Liu, Wenting Lu, Huafeng Fan, Meiling Xiao, Xiaoqiang Cui, Lu Li, Xiaoxin Zou, Weitao Zheng, Xiao Zhao","doi":"10.1021/acscatal.4c03060","DOIUrl":"https://doi.org/10.1021/acscatal.4c03060","url":null,"abstract":"Engineering the electronic structure and microenvironments of active sites is an effective strategy to enhance the oxygen evolution reaction (OER) kinetics. Meanwhile, most OER materials act only as precatalysts; therefore, understanding and modulation of restructuring kinetics is crucial for developing efficient OER active sites. Herein, a dopant-tuned restructuring kinetic for the generation of heterophase-confined metal-nonmetal diatomic sites has been achieved. Both operando spectra and theoretical evidence show that Zr dopants tune in situ restructuring kinetics and induce charge transfer between Ni and Se to generate Ni–Se diatomic sites that coordinate dynamically with oxygenated intermediates and reduce energy barriers significantly. Consequently, the dense Ni–Se diatomic sites display an overpotential of 224 mV vs reversible hydrogen electrode at 10 mAcm<sup>–2</sup> and stable operation over 500 h in alkaline conditions, one of the best performances among reported selenide-derived OER catalysts. Our results enable an in-depth understanding of dynamically restructured diatomic sites beyond the conventional single-metal sites and expand the strategies for engineering atomic/molecular-level active sites.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"107 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884502","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 : 2024-12-24DOI: 10.1021/acscatal.4c07240
Zhongyao Zhang, Sai Chen, Trenton Otto, Enrique Iglesia
Hydrogenation-dehydrogenation cycles enable the efficient storage, transport, and release of hydrogen via chemical means. Practical kinetic, thermodynamic, and H-density considerations make cyclic hydrocarbons the preferred organic hydrogen carriers. This study addresses the mechanism of methylcyclohexane (MCH) dehydrogenation to toluene (TOL), through methylcyclohexene (MCHE) intermediates on Pd nanoparticles (2–11 nm diameter) dispersed on Al2O3, SiO2, MgO, and CeO2. Turnovers occur on Pd surfaces densely covered with MCH-derived intermediates differing in isomeric structure and reactivity via sequential C–H activation elementary events, irrespective of nanoparticle size or support. The kinetically relevant step shifts from the second to the first H-abstraction step in MCH as temperature increases (from 453 to 553 K). The reactivity of Pd nanoparticle surfaces is insensitive to their size but supports with more competent Lewis acid–base (LAB) pairs lead to higher rates and stronger rate enhancements (relative to SiO2) with decreasing temperatures, which reflect the lower coverages of less reactive intermediates when supports can scavenge desorbable species. These dense adlayers retain interstices within which dehydrogenation turnovers occur, but no longer expose the most distinctive low-coordination atoms prevalent on small nanoparticles, leading to the observed structure insensitivity of turnover rates. The prevalence of such adlayers leads to surfaces without the saturation hydrogen coverages expected for Pd surfaces devoid of such organic species. These mechanistic insights are consistent with (i) the elimination of support effect by titration of LAB pairs; (ii) initial rate transients that are inhibited by competent supports; (iii) the relative reactivity of metal-free supports for dehydrogenation of MCHE and methylcyclohexadienes (but not MCH); and (iv) measured kinetic effects of MCH, MCHE, and H2 on turnover rates. The support effects provide strategies for maximizing the exposure of bare atom ensembles during dehydrogenation reactions. Its conceptual impact and practical significance are not restricted to the subject reaction in this study.
{"title":"Elementary Steps, Site Requirements, and Support Effects in Methylcyclohexane Dehydrogenation Reactions on Dispersed Pd Nanoparticles","authors":"Zhongyao Zhang, Sai Chen, Trenton Otto, Enrique Iglesia","doi":"10.1021/acscatal.4c07240","DOIUrl":"https://doi.org/10.1021/acscatal.4c07240","url":null,"abstract":"Hydrogenation-dehydrogenation cycles enable the efficient storage, transport, and release of hydrogen via chemical means. Practical kinetic, thermodynamic, and H-density considerations make cyclic hydrocarbons the preferred organic hydrogen carriers. This study addresses the mechanism of methylcyclohexane (MCH) dehydrogenation to toluene (TOL), through methylcyclohexene (MCHE) intermediates on Pd nanoparticles (2–11 nm diameter) dispersed on Al<sub>2</sub>O<sub>3</sub>, SiO<sub>2</sub>, MgO, and CeO<sub>2</sub>. Turnovers occur on Pd surfaces densely covered with MCH-derived intermediates differing in isomeric structure and reactivity via sequential C–H activation elementary events, irrespective of nanoparticle size or support. The kinetically relevant step shifts from the second to the first H-abstraction step in MCH as temperature increases (from 453 to 553 K). The reactivity of Pd nanoparticle surfaces is insensitive to their size but supports with more competent Lewis acid–base (LAB) pairs lead to higher rates and stronger rate enhancements (relative to SiO<sub>2</sub>) with decreasing temperatures, which reflect the lower coverages of less reactive intermediates when supports can scavenge desorbable species. These dense adlayers retain interstices within which dehydrogenation turnovers occur, but no longer expose the most distinctive low-coordination atoms prevalent on small nanoparticles, leading to the observed structure insensitivity of turnover rates. The prevalence of such adlayers leads to surfaces without the saturation hydrogen coverages expected for Pd surfaces devoid of such organic species. These mechanistic insights are consistent with (i) the elimination of support effect by titration of LAB pairs; (ii) initial rate transients that are inhibited by competent supports; (iii) the relative reactivity of metal-free supports for dehydrogenation of MCHE and methylcyclohexadienes (but not MCH); and (iv) measured kinetic effects of MCH, MCHE, and H<sub>2</sub> on turnover rates. The support effects provide strategies for maximizing the exposure of bare atom ensembles during dehydrogenation reactions. Its conceptual impact and practical significance are not restricted to the subject reaction in this study.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"23 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142880022","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 : 2024-12-24DOI: 10.1021/acscatal.4c07610
Koushani Kundu, Severin Haid, Moritz R. Schäfer, Wolfgang Frey, Johannes Kästner, Michael R. Buchmeiser
Stereoselective ring opening metathesis polymerization (ROMP) of enantiomerically pure 2,3-dicarbomethoxynorborn-5-ene ((+)-DCMNBE) was accomplished by the action of cationic tetra- and pentacoordinated molybdenum imido alkylidene cyclic alkyl amino carbene (CAAC) complexes that are chiral at molybdenum. The same catalysts were also utilized to perform the ROMP of 2,3-dimethoxymethylnorborn-5-ene ((+)-DMMNBE). All complexes were moderately to highly active and showed high trans-isoselectivity, offering up to 97% trans-isotactic (it) repeat units. In all cases, tetracoordinated complexes were the active species, resulting in pentacoordinated transition states. A theoretical model was elaborated using the buried volume (% Vbur) values of all ligands from single-crystal X-ray analysis together with the structures of the density functional theory (DFT) generated molybdacyclobutane intermediates. The model demonstrates the steric effects of all ligands at molybdenum on the trans-isoselectivity of the reaction, as predicted by the turnstile mechanism, and includes a positive correlation between the bulky CAAC ligand with high values of % Vbur of the other ligands and a high trans-isoselectivity. It was also successfully extended to molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes, proved to be of sufficient accuracy with a root mean squared error (RMSE) of 6.19% and was verified by Monte Carlo cross-validation (MCCV).
{"title":"Origin of Stereoselectivity in Ring Opening Metathesis Polymerization with Cationic Molybdenum Imido Alkylidene CAAC Complexes","authors":"Koushani Kundu, Severin Haid, Moritz R. Schäfer, Wolfgang Frey, Johannes Kästner, Michael R. Buchmeiser","doi":"10.1021/acscatal.4c07610","DOIUrl":"https://doi.org/10.1021/acscatal.4c07610","url":null,"abstract":"Stereoselective ring opening metathesis polymerization (ROMP) of enantiomerically pure 2,3-dicarbomethoxynorborn-5-ene ((+)-DCMNBE) was accomplished by the action of cationic tetra- and pentacoordinated molybdenum imido alkylidene cyclic alkyl amino carbene (CAAC) complexes that are chiral at molybdenum. The same catalysts were also utilized to perform the ROMP of 2,3-dimethoxymethylnorborn-5-ene ((+)-DMMNBE). All complexes were moderately to highly active and showed high <i>trans</i>-isoselectivity, offering up to 97% <i>trans</i>-isotactic (it) repeat units. In all cases, tetracoordinated complexes were the active species, resulting in pentacoordinated transition states. A theoretical model was elaborated using the buried volume (% V<sub>bur</sub>) values of all ligands from single-crystal X-ray analysis together with the structures of the density functional theory (DFT) generated molybdacyclobutane intermediates. The model demonstrates the steric effects of all ligands at molybdenum on the <i>trans</i>-isoselectivity of the reaction, as predicted by the turnstile mechanism, and includes a positive correlation between the bulky CAAC ligand with high values of % <i>V<sub>bur</sub></i> of the other ligands and a high <i>trans</i>-isoselectivity. It was also successfully extended to molybdenum imido alkylidene <i>N</i>-heterocyclic carbene (NHC) complexes, proved to be of sufficient accuracy with a root mean squared error (RMSE) of 6.19% and was verified by Monte Carlo cross-validation (MCCV).","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"33 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884505","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 : 2024-12-24DOI: 10.1021/acscatal.4c05779
Zhang Liu, Yanwei Wen, Zhaojie Wang, Limin Guo, Rong Chen, Aimin Zhang, Bin Shan
Highly dispersed transition metal atoms supported by reducible ceria have garnered considerable attention as CO preferential oxidation (PROX) catalysts. Dual-atom catalysts (DACs), which effectively balance activity and selectivity through synergistic effects, are promising candidates for PROX catalysis. We report here the high-throughput screening of CeO2(110)-supported DACs (MA-MB/CeO2, MA(B) = 3d, 4d, 5d transition metal) based on first-principles microkinetics. Reduced electronegativity and d-orbital population of metal atoms favor the stability of loaded DACs via binding energy and aggregation energy analyses. A state-to-state microkinetic analysis of the full PROX reaction network identifies that the O2 -predissociated Mars–van Krevelen (MvK) pathway, characterized by direct oxidation, carbonate formation, and interfacial oxygen migration, is the predominant mechanism on MA-MB/CeO2 under low temperatures. The key energetic routes of homogeneous DACs reveal that the oxygen removal energy of dissociated O2 and adsorption energies of CO and H on transition metal sites serve as effective descriptors of PROX performance. Following these insights, high-throughput computations of PROX descriptors are carried out on a combination of 435 heterogeneous DACs to screen catalysts with balanced activity and selectivity. Au-based DACs, notably Fe–Au, stand out at room temperature for their facile activation of dissociated oxygen and moderated hydrogen affinity. Our study harnesses the unique properties of dual-atom configurations and paves way for the rational design of efficient PROX catalysts.
{"title":"Synergistic Dual-Atom Catalysts on Ceria for Enhanced CO Preferential Oxidation: Insights from High-Throughput First-Principles Microkinetics","authors":"Zhang Liu, Yanwei Wen, Zhaojie Wang, Limin Guo, Rong Chen, Aimin Zhang, Bin Shan","doi":"10.1021/acscatal.4c05779","DOIUrl":"https://doi.org/10.1021/acscatal.4c05779","url":null,"abstract":"Highly dispersed transition metal atoms supported by reducible ceria have garnered considerable attention as CO preferential oxidation (PROX) catalysts. Dual-atom catalysts (DACs), which effectively balance activity and selectivity through synergistic effects, are promising candidates for PROX catalysis. We report here the high-throughput screening of CeO<sub>2</sub>(110)-supported DACs (M<sub>A</sub>-M<sub>B</sub>/CeO<sub>2</sub>, M<sub>A(B)</sub> = 3d, 4d, 5d transition metal) based on first-principles microkinetics. Reduced electronegativity and d-orbital population of metal atoms favor the stability of loaded DACs via binding energy and aggregation energy analyses. A state-to-state microkinetic analysis of the full PROX reaction network identifies that the O<sub>2</sub> -predissociated Mars–van Krevelen (MvK) pathway, characterized by direct oxidation, carbonate formation, and interfacial oxygen migration, is the predominant mechanism on M<sub>A</sub>-M<sub>B</sub>/CeO<sub>2</sub> under low temperatures. The key energetic routes of homogeneous DACs reveal that the oxygen removal energy of dissociated O<sub>2</sub> and adsorption energies of CO and H on transition metal sites serve as effective descriptors of PROX performance. Following these insights, high-throughput computations of PROX descriptors are carried out on a combination of 435 heterogeneous DACs to screen catalysts with balanced activity and selectivity. Au-based DACs, notably Fe–Au, stand out at room temperature for their facile activation of dissociated oxygen and moderated hydrogen affinity. Our study harnesses the unique properties of dual-atom configurations and paves way for the rational design of efficient PROX catalysts.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"14 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142880021","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}
Construction of C–C bonds utilizing challenging alkenyl alcohols employing first-row transition-metal catalysts is an unexplored area. Herein, we report the α-alkylation of ketones and nitriles using unactivated alkenyl alcohols as coupling partners in the presence of a phosphine-free pincer-NHC carbene-Mn(I) complex. This catalytic system was highly effective for the α-alkylation of a wide variety of ketones and acetonitriles having aromatic, heteroaromatic, and aliphatic units in the presence of several reducible functional groups. The practical applicability and synthetic value of this protocol were demonstrated through gram-scale synthesis, evaluation of green chemistry metrics, and functionalization of alkylated products into important molecules. Several control experiments, kinetic studies, and Hammett studies were carried out to understand the reaction mechanism, which was further supported by density functional theory (DFT) calculations.
{"title":"Pincer-(NHC)Mn(I) Complex-Catalyzed Selective α-Alkylation of Ketones and Nitriles Using Unactivated Alkenyl Alcohols","authors":"Adarsha Mandal, Manoj Pradhan, Chirantan Mitra, Srabani Nandi, Biswajit Sadhu, Sabuj Kundu","doi":"10.1021/acscatal.4c05889","DOIUrl":"https://doi.org/10.1021/acscatal.4c05889","url":null,"abstract":"Construction of C–C bonds utilizing challenging alkenyl alcohols employing first-row transition-metal catalysts is an unexplored area. Herein, we report the α-alkylation of ketones and nitriles using unactivated alkenyl alcohols as coupling partners in the presence of a phosphine-free pincer-NHC carbene-Mn(I) complex. This catalytic system was highly effective for the α-alkylation of a wide variety of ketones and acetonitriles having aromatic, heteroaromatic, and aliphatic units in the presence of several reducible functional groups. The practical applicability and synthetic value of this protocol were demonstrated through gram-scale synthesis, evaluation of green chemistry metrics, and functionalization of alkylated products into important molecules. Several control experiments, kinetic studies, and Hammett studies were carried out to understand the reaction mechanism, which was further supported by density functional theory (DFT) calculations.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"29 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884503","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 : 2024-12-24DOI: 10.1021/acscatal.4c06957
Luis Acuña-Saavedra, Ana María Méndez-Torres, Gloria Cárdenas-Jirón, Rubén Oñate, Benjamín Sánchez-Allende, Ricardo Venegas, Roberto Bernal, Francisco Melo, Elizabeth Imbarack, José H. Zagal, Ingrid Ponce
Perfluorinated iron phthalocyanine 16(F)FePc is probably the most active MN4 molecular catalyst reported to promote the oxygen reduction reaction (ORR) in alkaline media. Its high activity is attributed to the electron-withdrawing properties of the fluoro substituents, which promote a hard-iron active site to interact with a hard-O2 molecule. However, its activity has been explored shallowly. Here, we modified an edge plane-pyrolytic graphite surface (EPG) with 16(F)FePc to promote ORR in different pH media to build a Pourbaix diagram as an electrocatalytic roadmap for 16(F)FePc. Furthermore, the recently proposed reactivity descriptor for ORR, known as the “electrochemical hardness” (ΔEh), was determined in the EPG/16(F)FePc system at different pH. It was found that the catalyst’s reactivity is inversely proportional to the ΔEh values, so small values conduct to high activity. The same behavior was obtained for the oxidation–reduction hardness (ηox-red) parameter, which was theoretically determined in this work by DFT calculations. The theoretical ηox-red suggests a decrease of the Fe(II) reactivity with the increase of nitrogen atom protonation in the 16(F)FePc, supporting the pH-dependent ΔEh values. Moreover, a pH-dependent locked/unlocked mechanical switch behavior for the 16(F)FePc was determined, attributed to the iron center motion above the N4-plane without a demetalation process. We observed this phenomenon in an acid media using electrochemical techniques coupled with Surface-Enhanced Raman Spectroscopy (EC-SERS), monitoring the Fe(II)/(I), Fe(III)/(II) redox potentials, and the in situ ORR process. The scanning tunneling microscopy-based break junction technique (STM-BJ) revealed this mechanical switch at the single-molecule level. Conversely, the mechanical switch is locked in alkaline media, and the 16(F)FePc is in an on-catalytic state for ORR. Therefore, the unlocked mechanical switch could explain the low ORR catalytic activity of the 16(F)FePc in acidic media (off-catalytic state). These findings are crucial for understanding the catalytic behavior of 16(F)FePc, especially in acid media.
{"title":"The On/Off pH-Dependent Electrocatalytic Activity of the Perfluorinated Iron Phthalocyanine for the Oxygen Reduction Reaction and Electrochemical Hardness as a Reactivity Descriptor: Experimental and Theoretical Study","authors":"Luis Acuña-Saavedra, Ana María Méndez-Torres, Gloria Cárdenas-Jirón, Rubén Oñate, Benjamín Sánchez-Allende, Ricardo Venegas, Roberto Bernal, Francisco Melo, Elizabeth Imbarack, José H. Zagal, Ingrid Ponce","doi":"10.1021/acscatal.4c06957","DOIUrl":"https://doi.org/10.1021/acscatal.4c06957","url":null,"abstract":"Perfluorinated iron phthalocyanine 16(F)FePc is probably the most active MN<sub>4</sub> molecular catalyst reported to promote the oxygen reduction reaction (ORR) in alkaline media. Its high activity is attributed to the electron-withdrawing properties of the fluoro substituents, which promote a <i>hard-iron</i> active site to interact with a <i>hard-</i>O<sub>2</sub> molecule. However, its activity has been explored shallowly. Here, we modified an edge plane-pyrolytic graphite surface (EPG) with 16(F)FePc to promote ORR in different pH media to build a Pourbaix diagram as an electrocatalytic roadmap for 16(F)FePc. Furthermore, the recently proposed reactivity descriptor for ORR, known as the “electrochemical hardness” (Δ<i>E</i><sup><i>h</i></sup>), was determined in the EPG/16(F)FePc system at different pH. It was found that the catalyst’s reactivity is inversely proportional to the Δ<i>E</i><sup><i>h</i></sup> values, so small values conduct to high activity. The same behavior was obtained for the oxidation–reduction hardness (η<sub>ox-red</sub>) parameter, which was theoretically determined in this work by DFT calculations. The theoretical η<sub>ox-red</sub> suggests a decrease of the Fe(II) reactivity with the increase of nitrogen atom protonation in the 16(F)FePc, supporting the pH-dependent Δ<i>E</i><sup><i>h</i></sup> values. Moreover, a pH-dependent <i>locked</i>/<i>unlocked</i> mechanical switch behavior for the 16(F)FePc was determined, attributed to the iron center motion above the N<sub>4</sub>-plane without a demetalation process. We observed this phenomenon in an acid media using electrochemical techniques coupled with Surface-Enhanced Raman Spectroscopy (EC-SERS), monitoring the Fe(II)/(I), Fe(III)/(II) redox potentials, and the in situ ORR process. The scanning tunneling microscopy-based break junction technique (STM-BJ) revealed this mechanical switch at the single-molecule level. Conversely, the mechanical switch is <i>locked</i> in alkaline media, and the 16(F)FePc is in an <i>on-catalytic state</i> for ORR. Therefore, the <i>unlocked</i> mechanical switch could explain the low ORR catalytic activity of the 16(F)FePc in acidic media (<i>off-catalytic state</i>). These findings are crucial for understanding the catalytic behavior of 16(F)FePc, especially in acid media.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"57 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884536","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 : 2024-12-23DOI: 10.1021/acscatal.4c04758
Benjamin Bohigues, Isabel Millet, Patricia Concepción, Avelino Corma, Manuel Moliner, Pedro Serna
Small metal clusters can provide improved catalytic activity compared with single metal atoms and larger metal nanoparticles of the same element. The stabilization of metal ensembles of a few atoms is extremely challenging, however, because reductive sintering and oxidative fragmentation are phenomena that often occur at low temperatures in reactive atmospheres. In this regard, the CO oxidation reaction is particularly challenging because CO tends to aggregate noble metals on nonreducible supports, such as SiO2, whereas O2 triggers the formation of (less active) single atoms on reducible supports, such as CeO2. Accordingly, state-of-the-art Pt/CeO2 catalysts undergo severe deactivation under practical CO oxidation conditions in excess of O2. In this contribution, we report a highly active CO oxidation catalyst that is able to overcome both sintering and fragmentation instabilities under conditions that make other alternatives fail. The catalyst is based on small Pt clusters inside K-MFI that benefit from both strong metal/support interactions at defective sites of the zeolite and strong electronic promotion by the support, to attain highly stable, highly active, electron-rich Pt clusters.
{"title":"Highly Stable Subnanometric Pt Clusters in All Silica K-Doped Zeolites: Implications for the CO Oxidation Reaction","authors":"Benjamin Bohigues, Isabel Millet, Patricia Concepción, Avelino Corma, Manuel Moliner, Pedro Serna","doi":"10.1021/acscatal.4c04758","DOIUrl":"https://doi.org/10.1021/acscatal.4c04758","url":null,"abstract":"Small metal clusters can provide improved catalytic activity compared with single metal atoms and larger metal nanoparticles of the same element. The stabilization of metal ensembles of a few atoms is extremely challenging, however, because reductive sintering and oxidative fragmentation are phenomena that often occur at low temperatures in reactive atmospheres. In this regard, the CO oxidation reaction is particularly challenging because CO tends to aggregate noble metals on nonreducible supports, such as SiO<sub>2</sub>, whereas O<sub>2</sub> triggers the formation of (less active) single atoms on reducible supports, such as CeO<sub>2</sub>. Accordingly, state-of-the-art Pt/CeO<sub>2</sub> catalysts undergo severe deactivation under practical CO oxidation conditions in excess of O<sub>2</sub>. In this contribution, we report a highly active CO oxidation catalyst that is able to overcome both sintering and fragmentation instabilities under conditions that make other alternatives fail. The catalyst is based on small Pt clusters inside K-MFI that benefit from both strong metal/support interactions at defective sites of the zeolite and strong electronic promotion by the support, to attain highly stable, highly active, electron-rich Pt clusters.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"32 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142873846","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 : 2024-12-23DOI: 10.1021/acscatal.4c06623
Jesse R. Canavan, Justin A. Hopkins, Brandon L. Foley, Omar A. Abdelrahman, Paul J. Dauenhauer
Programmable catalysts exhibiting forced oscillation in the free energy of reacting surface species were simulated to understand the general mechanisms leading to efficient use of the input energy. Catalytic ratchets with either positive or negative adsorbate scaling exhibited oscillation conditions of both high and low turnover efficiency, yielding catalytic turnover frequencies either close to or significantly lower than the applied catalyst oscillation frequency, respectively. The “effective rate”, defined as the product of the catalytic turnover frequency and the turnover efficiency (ηTOE), was limited via two catalytic mechanisms: a leaky catalytic ratchet existed when molecules repeatedly traversed backward through the catalytic transition state upon catalyst oscillation, while a catalytic ratchet with low surface participation exhibited reduced formation of a gas-phase final product due to low surface product coverage. A single applied frequency yielding a maximum effective catalytic rate defined as the “resonance frequency” provided maximum combined benefit for catalytic rate and efficiency.
{"title":"Catalytic Resonance Theory: Turnover Efficiency and the Resonance Frequency","authors":"Jesse R. Canavan, Justin A. Hopkins, Brandon L. Foley, Omar A. Abdelrahman, Paul J. Dauenhauer","doi":"10.1021/acscatal.4c06623","DOIUrl":"https://doi.org/10.1021/acscatal.4c06623","url":null,"abstract":"Programmable catalysts exhibiting forced oscillation in the free energy of reacting surface species were simulated to understand the general mechanisms leading to efficient use of the input energy. Catalytic ratchets with either positive or negative adsorbate scaling exhibited oscillation conditions of both high and low turnover efficiency, yielding catalytic turnover frequencies either close to or significantly lower than the applied catalyst oscillation frequency, respectively. The “effective rate”, defined as the product of the catalytic turnover frequency and the turnover efficiency (η<sub>TOE</sub>), was limited via two catalytic mechanisms: a leaky catalytic ratchet existed when molecules repeatedly traversed backward through the catalytic transition state upon catalyst oscillation, while a catalytic ratchet with low surface participation exhibited reduced formation of a gas-phase final product due to low surface product coverage. A single applied frequency yielding a maximum effective catalytic rate defined as the “resonance frequency” provided maximum combined benefit for catalytic rate and efficiency.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"58 3 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142880024","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 : 2024-12-23DOI: 10.1021/acscatal.3c04684
Jessica L. Gomez-Lopez, Ashlee J. Davis, Timothy J. McClure, Mina Son, Daniel Steigerwald, Rebecca B. Watson, Mu-Hyun Baik, Corinna S. Schindler
Carbonyl–olefin metathesis reactions are powerful transformations for carbon–carbon bond formation. Despite recent progress, limitations exist that hamper the synthetic generality of the reported approaches. Catalytic systems that will enable tuning of their Lewis acidity and consequently the selective activation of specific substrate classes are expected to greatly enhance the current scope. We herein report the development of cationic iron-bis(oxazoline) complexes as powerful catalysts that enable the alteration of Lewis acidity to efficiently convert substrate types that were previously found to be incompatible with existing catalytic systems in carbonyl–olefin ring-closing metathesis.
{"title":"Bis(oxazoline) Iron Complexes Enable Tuning of Lewis Acidity for Catalytic Carbonyl–Olefin Metathesis","authors":"Jessica L. Gomez-Lopez, Ashlee J. Davis, Timothy J. McClure, Mina Son, Daniel Steigerwald, Rebecca B. Watson, Mu-Hyun Baik, Corinna S. Schindler","doi":"10.1021/acscatal.3c04684","DOIUrl":"https://doi.org/10.1021/acscatal.3c04684","url":null,"abstract":"Carbonyl–olefin metathesis reactions are powerful transformations for carbon–carbon bond formation. Despite recent progress, limitations exist that hamper the synthetic generality of the reported approaches. Catalytic systems that will enable tuning of their Lewis acidity and consequently the selective activation of specific substrate classes are expected to greatly enhance the current scope. We herein report the development of cationic iron-bis(oxazoline) complexes as powerful catalysts that enable the alteration of Lewis acidity to efficiently convert substrate types that were previously found to be incompatible with existing catalytic systems in carbonyl–olefin ring-closing metathesis.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"28 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142873845","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}
Rational design of metal oxide-type redox catalysts for selective propylene production is of paramount importance, yet remains challenging. This paper describes the structural and electronic effect of an alkaline earth metal promoter on lattice oxygen reactivity for chemical looping oxidative dehydrogenation (CL-ODH) of propane through the configuration of core–shell-type redox catalysts, which consist of a redox-active FeVO4 core and a selective mixed alkaline earth metal oxide shell. A systematic study demonstrates that Mg is the optimal promoter among all alkali and alkaline earth metals investigated, and the formed Mg2V2O7 outer shell provides a catalytic surface for C–H activation while blocking the nonselective sites for FeVO4, typically as an oxygen carrier. The core–shell redox catalyst with a higher coverage of the Mg2V2O7 layer achieves an enhanced propylene selectivity of 80.8% at an operation temperature of 550 °C. The design strategy highlights the exploration of alkaline earth metals in redox catalysts for chemical looping processes.
{"title":"Modulating Lattice Oxygen through an Alkaline Earth Metal Promoter for Chemical Looping Oxidative Dehydrogenation of Propane","authors":"Wei Wang, Sai Chen, Jiachen Sun, Ziyi Li, Xianhui Wang, Yiyi Xu, Zelin Wu, Donglong Fu, Chunlei Pei, Zhi-Jian Zhao, Jinlong Gong","doi":"10.1021/acscatal.4c06614","DOIUrl":"https://doi.org/10.1021/acscatal.4c06614","url":null,"abstract":"Rational design of metal oxide-type redox catalysts for selective propylene production is of paramount importance, yet remains challenging. This paper describes the structural and electronic effect of an alkaline earth metal promoter on lattice oxygen reactivity for chemical looping oxidative dehydrogenation (CL-ODH) of propane through the configuration of core–shell-type redox catalysts, which consist of a redox-active FeVO<sub>4</sub> core and a selective mixed alkaline earth metal oxide shell. A systematic study demonstrates that Mg is the optimal promoter among all alkali and alkaline earth metals investigated, and the formed Mg<sub>2</sub>V<sub>2</sub>O<sub>7</sub> outer shell provides a catalytic surface for C–H activation while blocking the nonselective sites for FeVO<sub>4</sub>, typically as an oxygen carrier. The core–shell redox catalyst with a higher coverage of the Mg<sub>2</sub>V<sub>2</sub>O<sub>7</sub> layer achieves an enhanced propylene selectivity of 80.8% at an operation temperature of 550 °C. The design strategy highlights the exploration of alkaline earth metals in redox catalysts for chemical looping processes.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"20 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142873848","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}