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Title: Operando Mechanistic Studies of CO2 Hydrogenation by Ruthenium Complexes Using High-Pressure NMR Spectroscopy

Journal Article · · ACS Catalysis

As a result of increased energy demands, the ability to both reduce carbon dioxide with dihydrogen to formate and conduct the reverse reaction with the same catalyst is of interest as a method for potential fuel generation and use. Ruthenium bis(diphosphine) complexes with and without pendant amines were reacted with mixtures of CO2/H2 gases in the presence of added base to catalytically yield formate; when the base was triethylamine, the reaction was found to be reversible. The reactions were monitored using high-pressure operando 1H and 31P{1H} NMR spectroscopy at 18 °C in THF under 40 atm of a 1:1 mixture of H2 and CO2. The rate of production of formate was correlated with the observation of specific organometallic species by NMR spectroscopy under catalytic conditions, including a hydrido–dihydrogen complex. From this operando study, a mechanism is proposed with two competing catalytic cycles for which the predominant cycle is dependent on which base and catalyst are used. Finally, the role of the base is shown to be vital for both catalytic rate and reversibility of the chemical transformation, indicating base selection should be carefully considered.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
Grant/Contract Number:
AC05-76RL01830
OSTI ID:
2340812
Report Number(s):
PNNL-SA--184605
Journal Information:
ACS Catalysis, Journal Name: ACS Catalysis Journal Issue: 23 Vol. 13; ISSN 2155-5435
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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