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Abstract Small molecule biomimetics inspired by the active site of the [FeFe]‐hydrogenase enzymes have shown promising electrocatalytic activity for hydrogen (H2) generation. However, most of the active‐site mimics based on [2Fe‐2S] clusters are not water‐soluble which limits the use of these electrocatalysts to organic media. Polymer‐supported [2Fe‐2S] systems, in particular, single‐site metallopolymer catalysts, have shown drastic improvements for electrocatalytic H2generation in aqueous milieu. [2Fe‐2S] complexes functionalized within well‐defined macromolecular supports via covalent bonding have demonstrated water solubility, enhanced site‐isolation, and improved chemical stability during catalysis. In this report, the synthesis of a new propanedithiolate (pdt)‐[2Fe‐2S] complex bearing a single α‐bromoester moiety for use in atom transfer radical polymerization (ATRP) is demonstrated as a novel metalloinitiator to prepare water‐soluble poly(2‐dimethylaminoethyl methacrylate) grafted (PDMAEMA‐g‐[2Fe‐2S]) metallopolymers. Using this approach, metallopolymers with controllable molecular weights (Mn= 5–40 kg mol−1) and low dispersity (Đ,Mw/Mn= 1.09–1.36) are prepared, which allows for the first time observation of the effect of the metallopolymers' chain length on the electrocatalytic activity. The ability to control the composition and molecular weight of these metallopolymers enables macromolecular engineering via ATRP of these materials to determine optimal structural features of metallopolymer catalysts for H2production.
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[FeFe]‐Hydrogenase Mimetic Metallopolymers with Enhanced Catalytic Activity for Hydrogen Production in Water
Abstract Electrocatalytic [FeFe]‐hydrogenase mimics for the hydrogen evolution reaction (HER) generally suffer from low activity, high overpotential, aggregation, oxygen sensitivity, and low solubility in water. By using atom‐transfer radical polymerization (ATRP), a new class of [FeFe]‐metallopolymers with precise molar mass, defined composition, and low polydispersity, has been prepared. The synthetic methodology introduced here allows facile variation of polymer composition to optimize the [FeFe] solubility, activity, and long‐term chemical and aerobic stability. Water soluble functional metallopolymers facilitate electrocatalytic hydrogen production in neutral water with loadings as low as 2 ppm and operate at rates an order of magnitude faster than hydrogenases (2.5×105 s−1), and with low overpotential requirement. Furthermore, unlike the hydrogenases, these systems are insensitive to oxygen during catalysis, with turnover numbers on the order of 40 000 under both anaerobic and aerobic conditions.
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- Award ID(s):
- 1664745
- PAR ID:
- 10072489
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 57
- Issue:
- 37
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 11898-11902
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Reviewed herein is the development of novel polymer‐supported [2Fe‐2S] catalyst systems for electrocatalytic and photocatalytic hydrogen evolution reactions. [FeFe] hydrogenases are the best known naturally occurring metalloenzymes for hydrogen generation, and small‐molecule, [2Fe‐2S]‐containing mimetics of the active site (H‐cluster) of these metalloenzymes have been synthesized for years. These small [2Fe‐2S] complexes have not yet reached the same capacity as that of enzymes for hydrogen production. Recently, modern polymer chemistry has been utilized to construct an outer coordination sphere around the [2Fe‐2S] clusters to provide site isolation, water solubility, and improved catalytic activity. In this review, the various macromolecular motifs and the catalytic properties of these polymer‐supported [2Fe‐2S] materials are surveyed. The most recent catalysts that incorporate a single [2Fe‐2S] complex, termed single‐site [2Fe‐2S] metallopolymers, exhibit superior activity for H2production.more » « less
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