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Title: Highly robust hydrogen generation by bio-inspired Ir complexes for dehydrogenation of formic acid in water: Experimental and theoretical mechanistic investigations at different pH

Hydrogen generation from formic acid (FA), one of the most promising hydrogen storage materials, has attracted much attention due to the demand for the development of renewable energy carriers. Catalytic dehydrogenation of FA in an efficient and green manner remains challenging. Here, we report a series of bio-inspired Ir complexes for highly robust and selective hydrogen production from FA in aqueous solutions without organic solvents or additives. One of these complexes bearing an imidazoline moiety (complex 6) achieved a turnover frequency (TOF) of 322,000 h⁻¹ at 100 °C, which is higher than ever reported. The novel catalysts are very stable and applicable in highly concentrated FA. For instance, complex 3 (1 μmol) affords an unprecedented turnover number (TON) of 2,050,000 at 60 °C. Deuterium kinetic isotope effect experiments and density functional theory (DFT) calculations employing a “speciation” approach demonstrated a change in the rate-determining step with increasing solution pH. This study provides not only more insight into the mechanism of dehydrogenation of FA but also offers a new principle for the design of effective homogeneous organometallic catalysts for H₂ generation from FA.
 [1] ;  [2] ;  [2] ;  [3] ;  [3] ;  [4] ;  [3] ;  [3] ;  [2] ;  [4]
  1. Dalian Univ. of Technology, Panjin (China)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan)
  4. National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan); Japan Science and Technology Agency, Saitama (Japan)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 2155-5435; R&D Project: CO026; KC0304030
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 3; Journal Issue: 36; Journal ID: ISSN 2155-5435
American Chemical Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY formic acid dehydrogenation; Ir complexes; mechanism; kinetic isotope effect; pH-dependence