10.1002/anie.201902218
Angewandte Chemie International Edition
COMMUNICATION
for CO. Control experiments under N2 (Fig. S15) and isotopic
labelling experiments (Fig. S16) confirmed CO2 as the origin of
CO. ATR-FTIR does not suggest modification or degradation of
P21, both upon immobilization and after CPE (Fig. S17).
development of catalyst-containing polymers with tailored
functionality toward catalytic activity, selectivity and stability.
The product selectivity of P21 is also
a significant
Acknowledgements
improvement relative to that of the molecular CotpyP catalyst,
which produces CO at 69% selectivity (CO/H2 = 2.3) on the
same electrode (Fig. S18). This highlights the possibility of
improving selectivity by modification to the outer coordination
sphere of a molecular catalyst rather than the catalyst’s primary
ligand structure.[9a, 9b] The relatively low turnover frequencies of
P21-based electrodes (~0.007 s−1) compares well with those of
CotpyP-based electrodes (~0.009 s−1), suggesting that the
polymeric scaffold does not impede catalysis. Similar kinetic
limitations were previously observed for other Co bis(terpyridine)
This work was supported by the Woolf Fisher Trust in New
Zealand (J. J. L.), the Winston Churchill Foundation of the
United States (J. A. V.), the Christian Doppler Research
Association (Austrian Federal Ministry for Digital and Economic
Affairs and the National Foundation for Research, Technology
and Development), the OMV Group (J. W., E. E. M., E. R.). We
also gratefully acknowledge Dr. Katarzyna P. Sokol, Dr. Dong
Heon Nam, Andreas Wagner and Kenichi Nakanishi for
providing electrode materials and Daniel Whitaker for help with
gel permeation chromatography measurements.
catalysts immobilized on electrodes in aqueous and MeCN
17]
electrolysis conditions,[11b,
which could originate from the
anchored catalyst’s reduced degrees of freedom or, in this case,
from the limited diffusion of CO2 within the porous electrodes.
As the most selective polymer toward CO production, P21
was immobilized on a p-type Si (Si) semiconductor electrode for
photoelectrochemical CO2 reduction. This was enabled by
interfacing a compatible IO-TiO2 layer with light-harvesting Si as
previously reported.[18]
Keywords: polymers • electrochemistry • catalysis • CO2
reduction • artificial photosynthesis
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Linear sweep voltammograms under chopped illumination
were conducted on the Si|IO-TiO2|P21 photocathode in the same
electrolyte solution as that used for the Ti|IO-TiO2|P21 cathodes
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In conclusion, rationally designed coordination polymers
have been demonstrated as a versatile platform to achieve
tunable molecular CO2 reduction catalysis in the presence of
water. By first modulating the degree of crosslinking via Co
loading in the polymer matrix, an equilibrium between mono(tpy)
and bis(tpy) complexes was established that ultimately favors
the more stable bis(tpy) complex and therefore electrocatalytic
CO evolution. Next, the choice of functional group monomer was
aimed toward the provision of an artificially engineered
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selective CO production. This was demonstrated by the
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photoelectrodes, where selective solar-driven CO2 reduction was
achieved. The strategy presented here motivates further
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