Pub Date : 2025-04-04DOI: 10.1021/acscatal.4c07870
Andrey N. Pravdivtsev, Ben J. Tickner, Stefan Glöggler, Jan-Bernd Hövener, Gerd Buntkowsky, Simon B. Duckett, Clifford R. Bowers, Vladimir V. Zhivonitko
Nuclear spin hyperpolarization utilizing parahydrogen has the potential for broad applications in chemistry, catalysis, biochemistry, and medicine. This review examines recent chemical and biochemical insights gained using parahydrogen-induced polarization (PHIP). We begin with photoinduced PHIP, which allows the investigation of short-lived and photoactivated catalysis. Next, we review the partially negative line effect, in which distinctive line shape helps to reveal information about rapid exchange with parahydrogen and the role of short-lived catalytic species. The NMR signal enhancement of a single proton in oneH-PHIP is discussed, challenging the underpinning concept of the necessity of pairwise hydrogenation. Furthermore, we examine metal-free PHIP facilitated by frustrated Lewis pair molecular tweezers and radicaloids, demonstrating alternative routes to hydrogenation. Although symmetric molecules incorporating parahydrogen are NMR silent, we showcase methods that reveal hyperpolarized states through post-hydrogenation reactions. We discuss chemical exchange processes that mediate polarization transfer between parahydrogen and a molecular target, expanding the reach of PHIP without synthesizing specialized precursors. We conclude this review by highlighting the role of PHIP in uncovering the H2 activation mechanisms of hydrogenases. By providing a detailed review of these diverse phenomena, we aim to familiarize the reader with the versatility of PHIP and its potential applications for mechanistic studies and chemical analysis.
{"title":"Unconventional Parahydrogen-Induced Hyperpolarization Effects in Chemistry and Catalysis: From Photoreactions to Enzymes","authors":"Andrey N. Pravdivtsev, Ben J. Tickner, Stefan Glöggler, Jan-Bernd Hövener, Gerd Buntkowsky, Simon B. Duckett, Clifford R. Bowers, Vladimir V. Zhivonitko","doi":"10.1021/acscatal.4c07870","DOIUrl":"https://doi.org/10.1021/acscatal.4c07870","url":null,"abstract":"Nuclear spin hyperpolarization utilizing parahydrogen has the potential for broad applications in chemistry, catalysis, biochemistry, and medicine. This review examines recent chemical and biochemical insights gained using parahydrogen-induced polarization (PHIP). We begin with photoinduced PHIP, which allows the investigation of short-lived and photoactivated catalysis. Next, we review the partially negative line effect, in which distinctive line shape helps to reveal information about rapid exchange with parahydrogen and the role of short-lived catalytic species. The NMR signal enhancement of a single proton in oneH-PHIP is discussed, challenging the underpinning concept of the necessity of pairwise hydrogenation. Furthermore, we examine metal-free PHIP facilitated by frustrated Lewis pair molecular tweezers and radicaloids, demonstrating alternative routes to hydrogenation. Although symmetric molecules incorporating parahydrogen are NMR silent, we showcase methods that reveal hyperpolarized states through post-hydrogenation reactions. We discuss chemical exchange processes that mediate polarization transfer between parahydrogen and a molecular target, expanding the reach of PHIP without synthesizing specialized precursors. We conclude this review by highlighting the role of PHIP in uncovering the H<sub>2</sub> activation mechanisms of hydrogenases. By providing a detailed review of these diverse phenomena, we aim to familiarize the reader with the versatility of PHIP and its potential applications for mechanistic studies and chemical analysis.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"89 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782731","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 low efficiency of photogenerated charge separation significantly hinders the photocatalytic nitrogen (N2) fixation. Local polarization electric field (LPEF) induced by defects has been known to enhance charge separation, yet the synergistic effects and mechanisms related to different types of defects in pure phases remain poorly understood. In this study, defect-free bismuth oxybromide (BiOBr; BOB), together with single vacancy (BOB-VBr and BOB-VO) and dual vacancy (BOB-VBrO) analogues, were successfully synthesized, and the presence of these specific vacancies was comprehensively characterized. Notably, the dual vacancy BOB-VBrO exhibited the highest photocatalytic NH3 generation rate of 266 μmol g–1 h–1 in a liquid–solid biphasic system, which was 6.1, 1.5, and 1.4 times higher than those of BOB, BOB-VBr, and BOB-VO, respectively. Furthermore, the NH3 generation capacity of BOB-VBrO reached an impressive rate of 978 μmol g–1 h–1 in a gas–liquid–solid triphasic system. Photoelectrochemical tests revealed that BOB-VBrO demonstrated the highest light conversion efficiency, followed by BOB-VO, BOB-VBr, and BOB. The relative intensity of the internal electric field in BOB-VBrO was also significantly high, being 1.8, 2.4, and 3.9 times greater than those of BOB-VO, BOB-VBr, and BOB, respectively. The Br and O vacancies synergistically induced LPEF between the [O]/[Br] and [Bi] layers. In situ irradiation X-ray photoelectron spectroscopy indicated that O and Br vacancies of the oligomers could synergistically enhance the LPEF, thereby facilitating the transfer of photogenerated electrons from O/Br to Bi. Additionally, the practical feasibility of BOB-VBrO in photocatalytic N2 fixation was validated to produce liquid nitrogenous fertilizer for plant growth, revealing its potential application in agricultural production.
{"title":"Oxygen and Bromine Vacancies Synergistically Induce Local Polarization Electric Field for Enhanced Photocatalytic Nitrogen Fixation on BiOBr","authors":"Zhou Zhong, Heng-Jian Zhang, Ya-Ying Yang, Tian-Kuan Zhang, Xing-Hua Qu, Li Ma, Hai-Lei Cao, Yi-Dong Hou, Jian Lü","doi":"10.1021/acscatal.5c00818","DOIUrl":"https://doi.org/10.1021/acscatal.5c00818","url":null,"abstract":"The low efficiency of photogenerated charge separation significantly hinders the photocatalytic nitrogen (N<sub>2</sub>) fixation. Local polarization electric field (LPEF) induced by defects has been known to enhance charge separation, yet the synergistic effects and mechanisms related to different types of defects in pure phases remain poorly understood. In this study, defect-free bismuth oxybromide (BiOBr; BOB), together with single vacancy (BOB-V<sub>Br</sub> and BOB-V<sub>O</sub>) and dual vacancy (BOB-V<sub>BrO</sub>) analogues, were successfully synthesized, and the presence of these specific vacancies was comprehensively characterized. Notably, the dual vacancy BOB-V<sub>BrO</sub> exhibited the highest photocatalytic NH<sub>3</sub> generation rate of 266 μmol g<sup>–1</sup> h<sup>–1</sup> in a liquid–solid biphasic system, which was 6.1, 1.5, and 1.4 times higher than those of BOB, BOB-V<sub>Br</sub>, and BOB-V<sub>O</sub>, respectively. Furthermore, the NH<sub>3</sub> generation capacity of BOB-V<sub>BrO</sub> reached an impressive rate of 978 μmol g<sup>–1</sup> h<sup>–1</sup> in a gas–liquid–solid triphasic system. Photoelectrochemical tests revealed that BOB-V<sub>BrO</sub> demonstrated the highest light conversion efficiency, followed by BOB-V<sub>O</sub>, BOB-V<sub>Br</sub>, and BOB. The relative intensity of the internal electric field in BOB-V<sub>BrO</sub> was also significantly high, being 1.8, 2.4, and 3.9 times greater than those of BOB-V<sub>O</sub>, BOB-V<sub>Br</sub>, and BOB, respectively. The Br and O vacancies synergistically induced LPEF between the [O]/[Br] and [Bi] layers. In situ irradiation X-ray photoelectron spectroscopy indicated that O and Br vacancies of the oligomers could synergistically enhance the LPEF, thereby facilitating the transfer of photogenerated electrons from O/Br to Bi. Additionally, the practical feasibility of BOB-V<sub>BrO</sub> in photocatalytic N<sub>2</sub> fixation was validated to produce liquid nitrogenous fertilizer for plant growth, revealing its potential application in agricultural production.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"25 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782769","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 capability of classical chiral cationic phase-transfer catalyst (ccPTC) in facilitating interphase transfer of inorganic bases for asymmetric synthesis has been well recognized. However, the combination of ccPTC with achiral Brønsted bases featuring wide-ranging basicity for asymmetric organic transformation is less explored, as the racemic background reaction promoted by such organo-soluble base is generally difficult to suppress. Here, we report a highly enantioselective phospha-Michael addition reaction mediated by the neutral base 4-dimethylaminopyridine (DMAP) and ccPTC bisguanidinium (BG), wherein the chiral cationic BG snatches the ionic nucleophile phosphinothioite from the protonated DMAP via a cation exchange process. The newly formed chiral ion pair resulted in the enhancement of the reactivity of the phosphinothioite and allowed it to undergo the subsequent enantiocontrolled addition pathway. The reaction furnishes α-chiral phosphine sulfides with high synthetic utility in high yields and enantioselectivities. Detailed mechanistic studies indicated the crucial impact of confined structural features and positive charge delocalization of chiral bisguanidinium on the reaction reactivity and stereoselective outcomes.
{"title":"Integrating Achiral Brønsted Base and Chiral Bisguanidinium for Enantioselective Phospha-Michael Addition to Chalcones","authors":"Zhenghao Wan, Hongjie Cao, Chao Wang, Choon-Hong Tan, Zhiping Zeng, Lili Zong","doi":"10.1021/acscatal.5c00918","DOIUrl":"https://doi.org/10.1021/acscatal.5c00918","url":null,"abstract":"The capability of classical chiral cationic phase-transfer catalyst (<b>ccPTC</b>) in facilitating interphase transfer of inorganic bases for asymmetric synthesis has been well recognized. However, the combination of <b>ccPTC</b> with achiral Brønsted bases featuring wide-ranging basicity for asymmetric organic transformation is less explored, as the racemic background reaction promoted by such organo-soluble base is generally difficult to suppress. Here, we report a highly enantioselective phospha-Michael addition reaction mediated by the neutral base 4-dimethylaminopyridine (<b>DMAP</b>) and <b>ccPTC</b> bisguanidinium (<b>BG</b>), wherein the chiral cationic <b>BG</b> snatches the ionic nucleophile phosphinothioite from the protonated <b>DMAP</b> via a cation exchange process. The newly formed chiral ion pair resulted in the enhancement of the reactivity of the phosphinothioite and allowed it to undergo the subsequent enantiocontrolled addition pathway. The reaction furnishes α-chiral phosphine sulfides with high synthetic utility in high yields and enantioselectivities. Detailed mechanistic studies indicated the crucial impact of confined structural features and positive charge delocalization of chiral bisguanidinium on the reaction reactivity and stereoselective outcomes.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"35 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782774","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 : 2025-04-03DOI: 10.1021/acscatal.4c06850
Nicole Segura-Salas, Rifael Z. Snitkoff-Sol, Danielle Ragonis, Sun-Myung Kim, Jan P. Hofmann, Ulrike I. Kramm, Lior Elbaz
Deciphering electrocatalytic processes with well-defined molecular catalysts is crucial for understanding complex reaction mechanisms. In this study, we investigated iron phthalocyanine (FePc) as a model catalyst for the CO2 reduction reaction (CO2RR). With direct current (dc) voltammetry, we described in detail the redox transitions of the catalyst and emphasized its importance for elucidating the formation of the activated catalytic site. The mechanism for CO2RR and HER was studied with Tafel plot analysis (dc-based) and Fourier-transformed alternating current voltammetry (FTacV). We showed the potential of FTacV as a technique to study catalytic processes vs dc techniques as it allowed us to observe the underlying electron transfer during CO2RR, revealing the formation of *CO2– and defining limiting steps in the reaction. These findings were compared against literature-based spectroscopic results on FePc to propose a possible mechanism. Overall, this work presents FTacV as a powerful tool for mechanistic studies in electrocatalysis, offering more profound insights into electron transfer dynamics during catalytic reactions.
{"title":"Deconvoluting HER from CO2RR on an FeN4-Derived Catalyst Using Fourier-Transformed Alternating Current Voltammetry","authors":"Nicole Segura-Salas, Rifael Z. Snitkoff-Sol, Danielle Ragonis, Sun-Myung Kim, Jan P. Hofmann, Ulrike I. Kramm, Lior Elbaz","doi":"10.1021/acscatal.4c06850","DOIUrl":"https://doi.org/10.1021/acscatal.4c06850","url":null,"abstract":"Deciphering electrocatalytic processes with well-defined molecular catalysts is crucial for understanding complex reaction mechanisms. In this study, we investigated iron phthalocyanine (FePc) as a model catalyst for the CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR). With direct current (dc) voltammetry, we described in detail the redox transitions of the catalyst and emphasized its importance for elucidating the formation of the activated catalytic site. The mechanism for CO<sub>2</sub>RR and HER was studied with Tafel plot analysis (dc-based) and Fourier-transformed alternating current voltammetry (FTacV). We showed the potential of FTacV as a technique to study catalytic processes vs dc techniques as it allowed us to observe the underlying electron transfer during CO<sub>2</sub>RR, revealing the formation of *CO<sub>2</sub><sup>–</sup> and defining limiting steps in the reaction. These findings were compared against literature-based spectroscopic results on FePc to propose a possible mechanism. Overall, this work presents FTacV as a powerful tool for mechanistic studies in electrocatalysis, offering more profound insights into electron transfer dynamics during catalytic reactions.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"62 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143766468","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 : 2025-04-03DOI: 10.1021/acscatal.4c07701
Haoyu Chen, Zhenbo Guo, Xuan Liang, Mei-Qi Zhang, Meng Wang, Ding Ma
Exploring the atom-economic transformation strategy for polyethylene terephthalate (PET), the most staple polyester material, can provide more approaches for the upcycling of plastic waste. Herein, we propose a one-pot process to convert PET into 1,4-cyclohexanedicarboxylic acid (CHDA) via the hydrogenation of terephthalic acid (TPA) by utilizing hydrogen stored in ethylene glycol (EG). The tandem process involving PET depolymerization, EG–H2O reforming, and TPA hydrogenation achieved high yields of CHDA (>90%) under optimized conditions. The employment of alkaline solution and combination of commercial Ru/C and Pd/C catalysts played critical roles in optimizing the reaction temperature and gaseous components so as to facilitate a one-pot reaction with enhanced hydrogen utilization. This method provides a feasible pathway for upcycling polyester waste, enabling high-selectivity product formation through efficient hydrogen utilization in a one-pot process.
{"title":"One-Pot Conversion of Polyethylene Terephthalate into 1,4-Cyclohexanedicarboxylic Acid without External H2","authors":"Haoyu Chen, Zhenbo Guo, Xuan Liang, Mei-Qi Zhang, Meng Wang, Ding Ma","doi":"10.1021/acscatal.4c07701","DOIUrl":"https://doi.org/10.1021/acscatal.4c07701","url":null,"abstract":"Exploring the atom-economic transformation strategy for polyethylene terephthalate (PET), the most staple polyester material, can provide more approaches for the upcycling of plastic waste. Herein, we propose a one-pot process to convert PET into 1,4-cyclohexanedicarboxylic acid (CHDA) via the hydrogenation of terephthalic acid (TPA) by utilizing hydrogen stored in ethylene glycol (EG). The tandem process involving PET depolymerization, EG–H<sub>2</sub>O reforming, and TPA hydrogenation achieved high yields of CHDA (>90%) under optimized conditions. The employment of alkaline solution and combination of commercial Ru/C and Pd/C catalysts played critical roles in optimizing the reaction temperature and gaseous components so as to facilitate a one-pot reaction with enhanced hydrogen utilization. This method provides a feasible pathway for upcycling polyester waste, enabling high-selectivity product formation through efficient hydrogen utilization in a one-pot process.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"37 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782779","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}
Catalytic NH3 decomposition has drawn growing interest in constructing the NH3-based hydrogen economy. Ni catalysts show great potential in this reaction but suffer from low atom utilization efficiency and unclear structure–activity relationship. Here, atomic layer deposition was used to grow Ni clusters on CeO2 nanorods to create a highly active catalyst for NH3 decomposition, which outperforms the conventional Ni nanoparticle catalysts and the synthesized Ni single-atom catalyst. The distinct catalytic behaviors of Ni clusters and Ni single atoms were systematically investigated. It is revealed that the interfacial confinement effect induces a strong electronic interaction between Ni clusters and CeO2, wherein abundant Ov-Ce3+ sites are formed in the vicinity of Ni clusters, resulting in interfacial electron-enriched Niδ− sites. These Niδ− sites bind to N adatoms moderately, favoring N–H bond cleavage and nitrogen desorption (the rate-determining step), which is the origin of the high activity. In contrast, ionic Ni single atoms diffusing into the CeO2 lattice display a much lower activity since strongly bound N adatoms block the active sites and retard the overall rate. This work provides a deep understanding of Ni-catalyzed NH3 decomposition and paves the way for designing high-performance metal catalysts for other structure-sensitive reactions.
{"title":"Electron-Enriched Ni Clusters Interfaced with CeO2 for Efficient H2 Production from NH3 Decomposition","authors":"Zhenwen Yang, Ziyi Shui, Mengfei Zhao, Zheng Wei, Fenglian Zhang, Xiaoxiao Duan, Ben Niu, Bingzhi Li, Guoxia Jiang, Zhengping Hao","doi":"10.1021/acscatal.5c00542","DOIUrl":"https://doi.org/10.1021/acscatal.5c00542","url":null,"abstract":"Catalytic NH<sub>3</sub> decomposition has drawn growing interest in constructing the NH<sub>3</sub>-based hydrogen economy. Ni catalysts show great potential in this reaction but suffer from low atom utilization efficiency and unclear structure–activity relationship. Here, atomic layer deposition was used to grow Ni clusters on CeO<sub>2</sub> nanorods to create a highly active catalyst for NH<sub>3</sub> decomposition, which outperforms the conventional Ni nanoparticle catalysts and the synthesized Ni single-atom catalyst. The distinct catalytic behaviors of Ni clusters and Ni single atoms were systematically investigated. It is revealed that the interfacial confinement effect induces a strong electronic interaction between Ni clusters and CeO<sub>2</sub>, wherein abundant O<sub>v</sub>-Ce<sup>3+</sup> sites are formed in the vicinity of Ni clusters, resulting in interfacial electron-enriched Ni<sup>δ−</sup> sites. These Ni<sup>δ−</sup> sites bind to N adatoms moderately, favoring N–H bond cleavage and nitrogen desorption (the rate-determining step), which is the origin of the high activity. In contrast, ionic Ni single atoms diffusing into the CeO<sub>2</sub> lattice display a much lower activity since strongly bound N adatoms block the active sites and retard the overall rate. This work provides a deep understanding of Ni-catalyzed NH<sub>3</sub> decomposition and paves the way for designing high-performance metal catalysts for other structure-sensitive reactions.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"25 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143766469","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}
In this work, we report the synthesis of stable half-sandwich two-legged Cp*Co(III)(N,O) complexes using donor-flexible pyridylidene-amine ligands, a deviation from the typical three-legged configuration of Cp*Co(III) complexes. In comparison to our previous report, wherein Cp*Co(III)-hydride species was inaccessible from the Cp*Co(III)(N,O)-alkoxy species ( ACS Catal.2021, 11, 11906–11920), this two-legged complex C-1 created a vacant coordination site at the cobalt(III) center, which was crucial for the formation of Cp*Co(III)(N,O)-hydride species (C-1-H) when treated with phenylsilane as a hydride donor. C-1-H exhibits versatile reactivity, enabling the selective deoxygenation of a variety of secondary amides, including aryl amides, acetanilide, and cyclic substrates. Moreover, the system demonstrates impressive chemoselectivity, as evidenced by the selective reduction of nitroarenes, N-phenyl urea, and the targeted deoxygenation of pharmaceutical derivatives such as paracetamol, indomethacin, and oxaprozin derivatives. The study also provides insight into the reaction mechanism, with DFT calculations confirming the role of in situ-generated cobalt hydride species as an active catalyst. This cobalt hydride is marginally more stable at triplet electronic state compared to that at the singlet state, which accounts for the experimental observation of the short-lived nature of the diamagnetic hydride species. Control experiments and kinetic profile agreed with the proposed mechanism.
{"title":"Two-Legged Cp*Co(III)(N,O) Complex as Stable Precatalyst for Selective Catalytic Deoxygenation of Secondary Amides","authors":"Priyanka Chakraborty, Sayan Dutta, Subhankar Pradhan, Nitu Kumari, Bholanath Maity, Luigi Cavallo, Basker Sundararaju","doi":"10.1021/acscatal.4c07512","DOIUrl":"https://doi.org/10.1021/acscatal.4c07512","url":null,"abstract":"In this work, we report the synthesis of stable half-sandwich two-legged Cp*Co(III)(N,O) complexes using donor-flexible pyridylidene-amine ligands, a deviation from the typical three-legged configuration of Cp*Co(III) complexes. In comparison to our previous report, wherein Cp*Co(III)-hydride species was inaccessible from the Cp*Co(III)(N,O)-alkoxy species ( <cite><i>ACS Catal.</i></cite> <span>2021</span>, <em>11</em>, 11906–11920), this two-legged complex <b>C-1</b> created a vacant coordination site at the cobalt(III) center, which was crucial for the formation of Cp*Co(III)(N,O)-hydride species (<b>C-1-</b><i><b>H</b></i>) when treated with phenylsilane as a hydride donor. <b>C-1-</b><i><b>H</b></i> exhibits versatile reactivity, enabling the selective deoxygenation of a variety of secondary amides, including aryl amides, acetanilide, and cyclic substrates. Moreover, the system demonstrates impressive chemoselectivity, as evidenced by the selective reduction of nitroarenes, <i>N</i>-phenyl urea, and the targeted deoxygenation of pharmaceutical derivatives such as paracetamol, indomethacin, and oxaprozin derivatives. The study also provides insight into the reaction mechanism, with DFT calculations confirming the role of <i>in situ</i>-generated cobalt hydride species as an active catalyst. This cobalt hydride is marginally more stable at triplet electronic state compared to that at the singlet state, which accounts for the experimental observation of the short-lived nature of the diamagnetic hydride species. Control experiments and kinetic profile agreed with the proposed mechanism.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"23 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782778","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 : 2025-04-03DOI: 10.1021/acscatal.4c07924
Haldrian Iriawan, Graham Leverick, Barış Alkan, Daniel Delgado, John Eom, Hongbin Xu, Sunmoon Yu, Livia Giordano, Annette Trunschke, Ifan E. L. Stephens, Yang Shao-Horn
The electrochemical oxidation of dinitrogen (N2) to nitrate (NO3–) is an attractive method for decentralized fertilizer production. Yet, scarce experimental evidence with trace NO3– produced in reported catalysts hints at the kinetics challenge and motivates a search for reliable electrocatalysts. We addressed the gaps in the understanding of N2 oxidation by computing three pathways: the (1) direct electrochemical pathway that extends all the way to NO3–, (2) surface lattice oxygen pathway on perovskites, and (3) surface-adsorbed oxygen pathway. These computations revealed the unfavorable trade-off between N2 activation and NO2 desorption/O vacancy filling step energies, which potentially limit the N2 oxidation activity and render the parasitic OER dominant. However, several oxides which possess reactive surface oxygen and inert/moderate OER activity were identified as more promising for experimental assessment. We then experimentally examined 20+ transition metal oxides, namely, ABO3 perovskites (A = La, Sr, Ca, Bi and B = Co, Mn, Fe) and MO2 rutiles (IrO2, RuO2, TiO2, SnO2, and Fe- and Ir-doped TiO2 and SnO2) in alkaline and neutral electrolytes. Electrochemical measurements via up to 22 h chronoamperometry showed minimal NO3– concentrations of <1 ppmN via UV–vis spectroscopy, which were comparable to those measured in the absence of N2. Time-dependent investigations of different substrates (i.e., carbon paper and Ti foil), increasing catalyst loadings in H-cells and flow cells, as well as high-surface-area La0.5Sr0.5CoO3 and La0.5Sr0.5MnO3 showed that the observed NO3– concentrations were not greater than those measured without N2 with experimental certainty. This work underscores the need for proliferating NOx production (massprod) beyond system size (masssys) or rigorous quantitative 15N2-labeling to provide concrete evidence for true N2 oxidation and encourages exploration of ambient N2 oxidation beyond conventional approaches.
{"title":"Assessing the Activity of Transition Metal Oxides for the Electrochemical N2 Oxidation to Nitrate","authors":"Haldrian Iriawan, Graham Leverick, Barış Alkan, Daniel Delgado, John Eom, Hongbin Xu, Sunmoon Yu, Livia Giordano, Annette Trunschke, Ifan E. L. Stephens, Yang Shao-Horn","doi":"10.1021/acscatal.4c07924","DOIUrl":"https://doi.org/10.1021/acscatal.4c07924","url":null,"abstract":"The electrochemical oxidation of dinitrogen (N<sub>2</sub>) to nitrate (NO<sub>3</sub><sup>–</sup>) is an attractive method for decentralized fertilizer production. Yet, scarce experimental evidence with trace NO<sub>3</sub><sup>–</sup> produced in reported catalysts hints at the kinetics challenge and motivates a search for reliable electrocatalysts. We addressed the gaps in the understanding of N<sub>2</sub> oxidation by computing three pathways: the (1) direct electrochemical pathway that extends all the way to NO<sub>3</sub><sup>–</sup>, (2) surface lattice oxygen pathway on perovskites, and (3) surface-adsorbed oxygen pathway. These computations revealed the unfavorable trade-off between N<sub>2</sub> activation and NO<sub>2</sub> desorption/O vacancy filling step energies, which potentially limit the N<sub>2</sub> oxidation activity and render the parasitic OER dominant. However, several oxides which possess reactive surface oxygen and inert/moderate OER activity were identified as more promising for experimental assessment. We then experimentally examined 20+ transition metal oxides, namely, ABO<sub>3</sub> perovskites (A = La, Sr, Ca, Bi and B = Co, Mn, Fe) and MO<sub>2</sub> rutiles (IrO<sub>2</sub>, RuO<sub>2</sub>, TiO<sub>2</sub>, SnO<sub>2</sub>, and Fe- and Ir-doped TiO<sub>2</sub> and SnO<sub>2</sub>) in alkaline and neutral electrolytes. Electrochemical measurements via up to 22 h chronoamperometry showed minimal NO<sub>3</sub><sup>–</sup> concentrations of <1 ppm<sub>N</sub> via UV–vis spectroscopy, which were comparable to those measured in the absence of N<sub>2</sub>. Time-dependent investigations of different substrates (i.e., carbon paper and Ti foil), increasing catalyst loadings in H-cells and flow cells, as well as high-surface-area La<sub>0.5</sub>Sr<sub>0.5</sub>CoO<sub>3</sub> and La<sub>0.5</sub>Sr<sub>0.5</sub>MnO<sub>3</sub> showed that the observed NO<sub>3</sub><sup>–</sup> concentrations were not greater than those measured without N<sub>2</sub> with experimental certainty. This work underscores the need for proliferating NO<sub><i>x</i></sub> production (mass<sub>prod</sub>) beyond system size (mass<sub>sys</sub>) or rigorous quantitative <sup>15</sup>N<sub>2</sub>-labeling to provide concrete evidence for true N<sub>2</sub> oxidation and encourages exploration of ambient N<sub>2</sub> oxidation beyond conventional approaches.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"18 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782780","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 : 2025-04-03DOI: 10.1021/acscatal.5c00393
Ashutosh Bhadouria, Ashmita Biswas, Brian M. Tackett
The recent abundance of ethane and propane feedstock and the simultaneous increase in electricity originating from wind and solar power present a transformative opportunity to decarbonize chemical manufacturing through the electrocatalytic production of essential chemicals. Achieving this goal will require significant improvements in fundamental understanding of electrocatalytic reactions of C2 and C3 hydrocarbons, which have only seen a resurgence in published studies over the past few years. In this Perspective, we aim to connect knowledge from a collection of such studies from the 1960s and 1970s to the most recent works today in order to accelerate electrocatalytic development for these molecular transformations. Reactions of saturated and unsaturated molecules are each analyzed in the context of (i) mechanisms, (ii) kinetics and catalyst composition, and (iii) electrolyte effects to highlight important considerations to improve activity and selectivity for each case. We hope readers find our bridge from the past to the present intriguing and of practical use in the pursuit of decarbonized chemical manufacturing.
{"title":"Electrocatalytic Transformations of C2 and C3 Hydrocarbons: Bridging from the Past to the Future","authors":"Ashutosh Bhadouria, Ashmita Biswas, Brian M. Tackett","doi":"10.1021/acscatal.5c00393","DOIUrl":"https://doi.org/10.1021/acscatal.5c00393","url":null,"abstract":"The recent abundance of ethane and propane feedstock and the simultaneous increase in electricity originating from wind and solar power present a transformative opportunity to decarbonize chemical manufacturing through the electrocatalytic production of essential chemicals. Achieving this goal will require significant improvements in fundamental understanding of electrocatalytic reactions of C<sub>2</sub> and C<sub>3</sub> hydrocarbons, which have only seen a resurgence in published studies over the past few years. In this Perspective, we aim to connect knowledge from a collection of such studies from the 1960s and 1970s to the most recent works today in order to accelerate electrocatalytic development for these molecular transformations. Reactions of saturated and unsaturated molecules are each analyzed in the context of (i) mechanisms, (ii) kinetics and catalyst composition, and (iii) electrolyte effects to highlight important considerations to improve activity and selectivity for each case. We hope readers find our bridge from the past to the present intriguing and of practical use in the pursuit of decarbonized chemical manufacturing.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"23 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143782827","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 : 2025-04-03DOI: 10.1021/acscatal.5c01683
Qi Ping, Yanru Zhu, Jian Zhang, Zhe An, Xin Shu, Hongyan Song, Jing He
In a heterogeneous catalytic reaction with strong heat release, the reaction exotherm causes a temperature increment and further has potential effects on product selectivity. This work focuses on syngas conversion, a representative strong exothermic reaction, to reveal a causation effect between the product distribution and the reaction exotherm. Owing to the thermodynamic characteristics that lead to higher heat release for methane or C2+ hydrocarbon formation than that for methanol or C2+ alcohol formation, the decrease in methanol or C2+ alcohol selectivity but increase in methane or C2+ hydrocarbon selectivity could increase the heat release and temperature increment (ΔT). It has been found that the distinguishing activation energies result in different kinetic sensitivities to heat. By decreasing ΔT, carbonyl insertion/C–C coupling reactions are boosted and hydrogenation of dissociated CO is suppressed, affording a significant decrease in methane selectivity and increase in C2+ alcohol and C2+ hydrocarbon selectivity. The activation energy of hydrogenation of nondissociated CO places in the middle among various reactions, leading to an insensitivity of methanol selectivity to the reaction exotherm in this system. The change in product distribution could further aggravate/weaken the heat release, showing a bilateral causality effect between the product distribution and reaction exotherm. Moreover, an optimized model has been developed for correlating the product selectivity (methane, C2+ hydrocarbon, methanol, or C2+ alcohol) with ΔT at a known setting temperature, which well predicts the sensitivity of the reaction exotherm to product distribution. This work innovates an approach to manipulate product distribution in intensely exothermic reactions via thermal management.
{"title":"Bilateral Causality Effects Between Product Distribution and Reaction Exotherm in the Conversion of Syngas","authors":"Qi Ping, Yanru Zhu, Jian Zhang, Zhe An, Xin Shu, Hongyan Song, Jing He","doi":"10.1021/acscatal.5c01683","DOIUrl":"https://doi.org/10.1021/acscatal.5c01683","url":null,"abstract":"In a heterogeneous catalytic reaction with strong heat release, the reaction exotherm causes a temperature increment and further has potential effects on product selectivity. This work focuses on syngas conversion, a representative strong exothermic reaction, to reveal a causation effect between the product distribution and the reaction exotherm. Owing to the thermodynamic characteristics that lead to higher heat release for methane or C<sub>2+</sub> hydrocarbon formation than that for methanol or C<sub>2+</sub> alcohol formation, the decrease in methanol or C<sub>2+</sub> alcohol selectivity but increase in methane or C<sub>2+</sub> hydrocarbon selectivity could increase the heat release and temperature increment (Δ<i>T</i>). It has been found that the distinguishing activation energies result in different kinetic sensitivities to heat. By decreasing Δ<i>T</i>, carbonyl insertion/C–C coupling reactions are boosted and hydrogenation of dissociated CO is suppressed, affording a significant decrease in methane selectivity and increase in C<sub>2+</sub> alcohol and C<sub>2+</sub> hydrocarbon selectivity. The activation energy of hydrogenation of nondissociated CO places in the middle among various reactions, leading to an insensitivity of methanol selectivity to the reaction exotherm in this system. The change in product distribution could further aggravate/weaken the heat release, showing a bilateral causality effect between the product distribution and reaction exotherm. Moreover, an optimized model has been developed for correlating the product selectivity (methane, C<sub>2+</sub> hydrocarbon, methanol, or C<sub>2+</sub> alcohol) with Δ<i>T</i> at a known setting temperature, which well predicts the sensitivity of the reaction exotherm to product distribution. This work innovates an approach to manipulate product distribution in intensely exothermic reactions via thermal management.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":"73 1","pages":""},"PeriodicalIF":12.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143766470","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}
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