Improving the photocatalytic reduction of CO2 to CO through immobilization of a molecular Re catalyst on TiO2
Author(s)Windle, Christopher D.
Whitwood, Adrian C.
Durrant, James R.
Perutz, Robin N.
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AbstractThis is the final published version. It first appeared in Chemistry - a European Journal, 2015, 21, 3746 – 3754, DOI: 10.1002/chem.201405041
The photocatalytic activity of phosphonated Re complexes, [Re(2,2’-
bipyridine-4,4’-bisphosphonic acid)(CO)3(L)] (ReP) with L = 3-picoline, or L =
bromide, immobilized on TiO2 nanoparticles is reported. The heterogenized Re
catalyst on the semiconductor, ReP-TiO2 hybrid, displays an improvement in CO2
reduction photocatalysis. A high turnover number (TON) of 48 mol CO (mol Re)–1
was observed in DMF with the electron donor triethanolamine at λ > 420 nm, which
compares favourably to previously reported homogeneous systems and is the highest
TON observed with a CO2 reducing Re catalyst under visible light in the absence of
an additional molecular dye. Photocatalytic CO2 reduction could even be observed
with ReP-TiO2 using wavelengths λ > 495 nm. Infrared and X-ray photoelectron
spectroscopies confirmed that an intact ReP catalyst is present on the TiO2 surface
before and during catalysis. Transient absorption spectroscopy suggests that the high
activity upon heterogenization is due to an increase in the lifetime of the immobilized
anionic Re intermediate (t50% > 1 s for ReP-TiO2 compared with t50% = 60 ms for ReP
in solution) and immobilization might also reduce the formation of inactive Re dimers.
This study demonstrates that the activity of a homogenous photocatalyst can be
improved through immobilization on a metal oxide surface by favorably modifying its
Financial support from the EPSRC (EP/H00338X/2 to E.R.; studentship and Doctoral
Prize to C.D.W.; DTP scholarship to E.P.), the Christian Doppler Research
Association (Austrian Federal Ministry of Science, Research and Economy and the
National Foundation for Research, Technology and Development) and the OMV
Group (to E.R.), the ERC (project Intersolar to J.D.) and the European Commission
Marie Curie CIG (PCIG10-GA-2011-303650 to A.R.) is gratefully acknowledged.