mz8b00765_si_001.pdf (1.9 MB)
Macromolecular Engineering of the Outer Coordination Sphere of [2Fe-2S] Metallopolymers to Enhance Catalytic Activity for H2 Production
journal contribution
posted on 2018-11-08, 20:15 authored by William
P. Brezinski, Metin Karayilan, Kayla E. Clary, Keelee C. McCleary-Petersen, Liye Fu, Krzysztof Matyjaszewski, Dennis H. Evans, Dennis L. Lichtenberger, Richard S. Glass, Jeffrey PyunSmall-molecule
catalysts inspired by the active sites of [FeFe]-hydrogenase
enzymes have long struggled to achieve fast rates of hydrogen evolution,
long-term stability, water solubility, and oxygen compatibility. We
profoundly improved on these deficiencies by grafting polymers from
a metalloinitiator containing a [2Fe-2S] moiety to form water-soluble
poly(2-dimethylamino)ethyl methacrylate metallopolymers (PDMAEMA-g-[2Fe-2S]) using atom transfer radical polymerization
(ATRP). This study illustrates the critical role of the polymer composition
in enhancing hydrogen evolution and aerobic stability by comparing
the catalytic activity of PDMAEMA-g-[2Fe-2S] with a nonionic water-soluble metallopolymer based on poly(oligo(ethylene
glycol) methacrylate) prepared via ATRP (POEGMA-g-[2Fe-2S]) with the same [2Fe-2S] metalloinitiator. Additionally,
the tunability of catalyst activity is demonstrated by the synthesis
of metallocopolymers incorporating the 2-(dimethylamino)ethyl methacrylate
(DMAEMA) and oligo(ethylene glycol) methacrylate (OEGMA) monomers.
Electrochemical investigations into these metallo(co)polymers show
that PDMAEMA-g-[2Fe-2S] retains complete
aerobic stability with catalytic current densities in excess of 20
mA·cm–2, while POEGMA-g-[2Fe-2S] fails to reach 1 mA·cm–2 current
density even with the application of high overpotentials (η
> 0.8 V) and loses all activity in the presence of oxygen. Random
copolymers of the two monomers polymerized with the same [2Fe-2S]
initiator showed intermediate activity in terms of current density,
overpotential, and aerobic stability.