title: Improving the photocatalytic reduction of CO2 to CO through immobilisation of a molecular Re catalyst on TiO2.
abstract: The photocatalytic activity of phosphonated Re complexes, [Re(2,2'-bipyridine-4,4'-bisphosphonic acid) (CO)3(L)] (ReP; L = 3-picoline or bromide) immobilised on TiO2 nanoparticles is reported. The heterogenised Re catalyst on the semiconductor, ReP-TiO2 hybrid, displays an improvement in CO2 reduction photocatalysis. A high turnover number (TON) of 48 molCO molRe(-1) is observed in DMF with the electron donor triethanolamine at λ>420 nm. ReP-TiO2 compares favourably to previously reported homogeneous systems and is the highest TON reported to date for a CO2-reducing Re photocatalyst under visible light irradiation. Photocatalytic CO2 reduction is even observed with ReP-TiO2 at wavelengths of λ>495 nm. Infrared and X-ray photoelectron spectroscopies confirm that an intact ReP catalyst is present on the TiO2 surface before and during catalysis. Transient absorption spectroscopy suggests that the high activity upon heterogenisation is due to an increase in the lifetime of the immobilised anionic Re intermediate (t50% >1 s for ReP-TiO2 compared with t50% = 60 ms for ReP in solution) and immobilisation might also reduce the formation of inactive Re dimers. This study demonstrates that the activity of a homogeneous photocatalyst can be improved through immobilisation on a metal oxide surface by favourably modifying its photochemical kinetics.
authors: Christian Doppler Laboratory for Sustainable SynGas Chemistry, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (U.K.); Department of Chemistry, University of York, Heslington, York YO10 5DD (U.K.).
authors: Christopher D
authors: CD
authors: Windle
authors: Ernest
authors: E
authors: Pastor
authors: Anna
authors: A
authors: Reynal
authors: Adrian C
authors: AC
authors: Whitwood
authors: Yana
authors: Y
authors: Vaynzof
authors: James R
authors: JR
authors: Durrant
authors: Robin N
authors: RN
authors: Perutz
authors: Erwin
authors: E
authors: Reisner
keywords: CO2 reduction; heterogeneous catalysis; immobilisation; photocatalysis; time-resolved spectroscopy
references: Chem Rev. 2007 May;107(5):1692-744
references: 17488058
references: Dalton Trans. 2012 Apr 28;41(16):5026-37
references: 22415540
references: J Am Chem Soc. 2003 Oct 1;125(39):11976-87
references: 14505419
references: J Phys Chem Lett. 2012 Feb 16;3(4):486-92
references: 26286052
references: Inorg Chem. 2011 Apr 4;50(7):2738-47
references: 21391575
references: J Am Chem Soc. 2008 Apr 30;130(17):5632-3
references: 18393497
references: Inorg Chem. 2011 Dec 5;50(23):11877-89
references: 22043811
references: Chem Commun (Camb). 2011 Feb 14;47(6):1695-7
references: 21212905
references: Chem Commun (Camb). 2014 May 4;50(34):4462-4
references: 24660220
references: Inorg Chem. 2013 Oct 21;52(20):11902-9
references: 24083376
references: Inorg Chem. 2005 Apr 4;44(7):2326-36
references: 15792468
references: Chem Commun (Camb). 2012 Aug 25;48(66):8189-91
references: 22785349
references: Dalton Trans. 2009 Feb 14;(6):983-93
references: 19173081
references: ChemSusChem. 2014 Mar;7(3):785-94
references: 24678062
references: Chemistry. 2011 Apr 4;17(15):4313-22
references: 21374746
references: Chemistry. 2008;14(10):3006-12
references: 18257003
references: J Am Chem Soc. 2009 Dec 30;131(51):18457-66
references: 19928857
references: Phys Chem Chem Phys. 2012 Jun 14;14(22):8192-8
references: 22549294
references: Photochem Photobiol Sci. 2007 Apr;6(4):454-61
references: 17404641
references: Phys Chem Chem Phys. 2014 Apr 7;16(13):5922-6
references: 24566893
references: J Am Chem Soc. 2011 May 11;133(18):6922-5
references: 21504161
references: J Am Chem Soc. 2010 Feb 24;132(7):2132-3
references: 20121138
references: Chem Commun (Camb). 2012 Jul 28;48(59):7374-6
references: 22714095
references: Angew Chem Int Ed Engl. 2012 Dec 14;51(51):12749-53
references: 23169697
references: J Am Chem Soc. 2014 Mar 12;136(10):4003-11
references: 24571655
references: Chemistry. 2012 Nov 26;18(48):15464-75
references: 23033059
references: Inorg Chem. 2008 Dec 1;47(23):10801-3
references: 18986137
references: Angew Chem Int Ed Engl. 2013 Jan 14;52(3):988-92
references: 23197479
references: J Phys Chem A. 2007 Jul 26;111(29):6832-42
references: 17518452
references: J Am Chem Soc. 2013 Nov 13;135(45):16825-8
references: 24156658
references: J Am Chem Soc. 2014 Apr 23;136(16):6021-30
references: 24689747
references: Inorg Chem. 2013 May 20;52(10):5889-96
references: 23651366
references: Inorg Chem. 2010 Oct 18;49(20):9283-9
references: 20845978
references: Annu Rev Phys Chem. 2012;63:541-69
references: 22404587
references: Science. 2012 Oct 5;338(6103):90-4
references: 23042890
references: J Am Chem Soc. 2003 Jan 15;125(2):475-82
references: 12517161
references: J Appl Crystallogr. 2011 Dec 1;44(Pt 6):1259-1263
references: 22199401
references: J Am Chem Soc. 2008 Feb 13;130(6):2023-31
references: 18205359
references: J Am Chem Soc. 2013 Mar 27;135(12):4596-9
references: 23470246