Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Selectivity control of CO versus HCOO production in the visible-light-driven catalytic reduction of CO2 with two cooperative metal sites

A Publisher Correction to this article was published on 28 August 2019

This article has been updated


It is highly desirable to discover molecular catalysts with controlled selectivity for visible-light-driven CO2 reduction to fuels. In the design of catalysts employing earth-abundant metals, progress has been made for CO production, but formate generation has been observed more rarely. Here, we report a binuclear Co complex bearing a bi-quaterpyridine ligand that can selectively reduce CO2 to HCOO or CO under visible light irradiation. Selective formate production (maximum of 97%) was obtained with a turnover number of up to 821 in basic acetonitrile solution. Conversely, in the presence of a weak acid, CO2 reduction affords CO with high selectivity (maximum of 99%) and a maximum turnover number of 829. The catalytic process is controlled by the two Co atoms acting synergistically, and the selectivity can be steered towards the desired product by simply changing the acid co-substrate.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Structure of compounds used in this study.
Fig. 2: Crystal structure of [Co2(biqpy)Cl(MeOH)(H2O)]3+.
Fig. 3: Photocatalytic CO2 reduction products.
Fig. 4: CV plots and infrared SEC spectra.
Fig. 5: Proposed mechanism for visible-light-driven catalytic reduction of CO2 into CO and HCOO with catalyst 1.

Data availability

Crystallographic data for [Co2(biqpy)Cl(MeOH)(H2O)](ClO4)3 have been deposited at the Cambridge Crystallographic Data Centre (CCDC no. 1858669. The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Change history

  • 28 August 2019

    An amendment to this paper has been published and can be accessed via a link at the top of the paper.


  1. 1.

    Aresta, M., Dibenedetto, A. & Angelini, A. Catalysis for the valorization of exhaust carbon: from CO2 to chemicals, materials and fuels. Technological use of CO2. Chem. Rev. 114, 1709–1742 (2014).

    CAS  Article  Google Scholar 

  2. 2.

    Jhong, H.-R. M., Ma, S. & Kenis, P. J. A. Electrochemical conversion of CO2 to useful chemicals: current status, remaining challenges and future opportunities. Curr. Opin. Chem. Eng. 2, 191–199 (2013).

    Article  Google Scholar 

  3. 3.

    Seh, Z. W. et al. Combining theory and experiment in electrocatalysis: insights into materials design. Science 355, eaad4998 (2017).

    Article  Google Scholar 

  4. 4.

    Fujita, E. Photochemical carbon dioxide reduction with metal complexes. Coord. Chem. Rev. 185–186, 373–384 (1999).

    Article  Google Scholar 

  5. 5.

    Tamaki, Y., Morimoto, T., Koike, K. & Ishitani, O. Photocatalytic CO2 reduction with high turnover frequency and selectivity of formic acid formation using Ru(ii) multinuclear complexes. Proc. Natl Acad. Sci. USA 109, 15673–15678 (2012).

    CAS  Article  Google Scholar 

  6. 6.

    Rosas-Hernández, A., Junge, H. & Beller, M. Photochemical reduction of carbon dioxide to formic acid using ruthenium(ii)-based catalysts and visible light. ChemCatChem 7, 3316–3321 (2015).

    Article  Google Scholar 

  7. 7.

    Tamaki, Y., Koike, K. & Ishitani, O. Highly efficient, selective, and durable photocatalytic system for CO2 reduction to formic acid. Chem. Sci. 6, 7213–7221 (2015).

    CAS  Article  Google Scholar 

  8. 8.

    Sato, S., Morikawa, T., Kajino, T. & Ishitani, O. A highly efficient mononuclear iridium complex photocatalyst for CO2 reduction under visible light. Angew. Chem. Int. Ed. 52, 988–992 (2013).

    CAS  Article  Google Scholar 

  9. 9.

    Reithmeier, R. O. et al. Mono- and bimetallic Ir(iii) based catalysts for the homogeneous photocatalytic reduction of CO2 under visible light irradiation. New insights into catalyst deactivation. Dalton Trans. 43, 13259–13269 (2014).

    CAS  Article  Google Scholar 

  10. 10.

    Reithmeier, R. O., Meister, S., Siebel, A. & Rieger, B. Synthesis and characterization of a trinuclear iridium(iii) based catalyst for the photocatalytic reduction of CO2. Dalton Trans. 44, 6466–6472 (2015).

    CAS  Article  Google Scholar 

  11. 11.

    Hawecker, J., Lehn, J.-M. & Ziessel, R. Efficient photochemical reduction of CO2 to CO by visible light irradiation of systems containing Re(bipy)(CO)3X or Ru(bipy)3 2+–Co2+ combinations as homogeneous catalysts. J. Chem. Soc. Chem. Commun. 536–538 (1983).

  12. 12.

    Takeda, H., Koike, K., Inoue, H. & Ishitani, O. Development of an efficient photocatalytic system for CO2 reduction using rhenium(i) complexes based on mechanistic studies. J. Am. Chem. Soc. 130, 2023–2031 (2008).

    CAS  Article  Google Scholar 

  13. 13.

    Takeda, H. & Ishitani, O. Development of efficient photocatalytic systems for CO2 reduction using mononuclear and multinuclear metal complexes based on mechanistic studies. Coord. Chem. Rev. 254, 346–354 (2010).

    CAS  Article  Google Scholar 

  14. 14.

    Agarwal, J., Fujita, E., Schaefer, H. F. & Muckerman, J. T. Mechanisms for CO production from CO2 using reduced rhenium tricarbonyl catalysts. J. Am. Chem. Soc. 134, 5180–5186 (2012).

    CAS  Article  Google Scholar 

  15. 15.

    Yamazaki, Y., Takeda, H. & Ishitani, O. Photocatalytic reduction of CO2 using metal complexes. J. Photochem. Photobiol. C 25, 106–137 (2015).

    CAS  Article  Google Scholar 

  16. 16.

    Lehn, J.-M. & Ziessel, R. Photochemical generation of carbon monoxide and hydrogen by reduction of carbon dioxide and water under visible light irradiation. Proc. Natl Acad. Sci. USA 79, 701–704 (1982).

    CAS  Article  Google Scholar 

  17. 17.

    Varma, S. et al. Efficient photocatalytic hydrogen production in water using a cobalt(iii) tetraaza-macrocyclic catalyst: electrochemical generation of the low-valent Co(i) species and its reactivity toward proton reduction. Phys. Chem. Chem. Phys. 15, 17544–17552 (2013).

    CAS  Article  Google Scholar 

  18. 18.

    Chan, S. L.-F., Lam, T. L., Yang, C., Yan, S.-C. & Cheng, N. M. A robust and efficient cobalt molecular catalyst for CO2 reduction. Chem. Commun. 51, 7799–7801 (2015).

    CAS  Article  Google Scholar 

  19. 19.

    Chen, L. et al. Molecular catalysis of the electrochemical and photochemical reduction of CO2 with earth-abundant metal complexes. selective production of CO vs HCOOH by switching of the metal center. J. Am. Chem. Soc. 137, 10918–10921 (2015).

    CAS  Article  Google Scholar 

  20. 20.

    Tinnemans, A. H. A., Koster, T. P. M., Thewissen, D. H. M. W. & Mackor, A. Tetraaza-macrocyclic cobalt(ii) and nickel(ii) complexes as electron-transfer agents in the photo(electro)chemical and electrochemical reduction of carbon dioxide. Recl. Trav. Chim. Pays-Bas 103, 288–295 (1984).

    CAS  Article  Google Scholar 

  21. 21.

    Thoi, V. S., Kornienko, N., Margarit, C. G., Yang, P. & Chang, C. J. Visible-light photoredox catalysis: selective reduction of carbon dioxide to carbon monoxide by a nickel N-heterocyclic carbene–isoquinoline complex. J. Am. Chem. Soc. 135, 14413–14424 (2013).

    CAS  Article  Google Scholar 

  22. 22.

    Bonin, J., Robert, M. & Routier, M. Selective and efficient photocatalytic CO2 reduction to CO using visible light and an iron-based homogeneous catalyst. J. Am. Chem. Soc. 136, 16768–16771 (2014).

    CAS  Article  Google Scholar 

  23. 23.

    Takeda, H., Ohashi, K., Sekine, A. & Ishitani, O. Photocatalytic CO2 reduction using Cu(i) photosensitizers with a Fe(ii) catalyst. J. Am. Chem. Soc. 138, 4354–4357 (2016).

    CAS  Article  Google Scholar 

  24. 24.

    Alsabeh, P. G. et al. Iron-catalyzed photoreduction of carbon dioxide to synthesis gas. Catal. Sci. Technol. 6, 3623–3630 (2016).

    CAS  Article  Google Scholar 

  25. 25.

    Rao, H., Schmidt, L. C., Bonin, J. & Robert, M. Visible-light-driven methane formation from CO2 with a molecular iron catalyst. Nature 548, 74 (2017).

    CAS  Article  Google Scholar 

  26. 26.

    Takeda, H., Koizumi, H., Okamoto, K. & Ishitani, O. Photocatalytic CO2 reduction using a Mn complex as a catalyst. Chem. Commun. 50, 1491–1493 (2014).

    CAS  Article  Google Scholar 

  27. 27.

    Torralba-Peñalver, E., Luo, Y., Compain, J.-D., Chardon-Noblat, S. & Fabre, B. Selective catalytic electroreduction of CO2 at silicon nanowires (SiNWs) photocathodes using non-noble metal-based manganese carbonyl bipyridyl molecular catalysts in solution and grafted onto SiNWs. ACS Catal. 5, 6138–6147 (2015).

    Article  Google Scholar 

  28. 28.

    Fei, H., Sampson, M. D., Lee, Y., Kubiak, C. P. & Cohen, S. M. Photocatalytic CO2 reduction to formate using a Mn(i) molecular catalyst in a robust metal–organic framework. Inorg. Chem. 54, 6821–6828 (2015).

    CAS  Article  Google Scholar 

  29. 29.

    Cheung, P. L., Machan, C. W., Malkhasian, A. Y. S., Agarwal, J. & Kubiak, C. P. Photocatalytic reduction of carbon dioxide to CO and HCO2H using fac-Mn(CN)(bpy)(CO)3. Inorg. Chem. 55, 3192–3198 (2016).

    CAS  Article  Google Scholar 

  30. 30.

    Guo, Z. et al. Photocatalytic conversion of CO2 to CO by a copper(ii) quaterpyridine complex. ChemSusChem 10, 4009–4013 (2017).

    CAS  Article  Google Scholar 

  31. 31.

    Liu, W. J. et al. A copper(ii) molecular catalyst for efficient and selective photochemical reduction of CO2 to CO in a water-containing system. Chem. Eur. J. 24, 4503–4508 (2018).

    CAS  Article  Google Scholar 

  32. 32.

    Boston, D. J., Xu, C., Armstrong, D. W. & MacDonnell, F. M. Photochemical reduction of carbon dioxide to methanol and formate in a homogeneous system with pyridinium catalysts. J. Am. Chem. Soc. 135, 16252–16255 (2013).

    CAS  Article  Google Scholar 

  33. 33.

    Takeda, H., Cometto, C., Ishitani, O. & Robert, M. Electrons, photons, protons and earth-abundant metal complexes for molecular catalysis of CO2 reduction. ACS Catal. 7, 70–88 (2017).

    CAS  Article  Google Scholar 

  34. 34.

    Rao, H., Bonin, J. & Robert, M. Toward visible-light photochemical CO2-to-CH4 conversion in aqueous solutions using sensitized molecular catalysis. J. Phys. Chem. C. 122, 13834–13839 (2018).

    CAS  Article  Google Scholar 

  35. 35.

    Mellmann, D., Sponholz, P., Junge, H. & Beller, M. Formic acid as a hydrogen storage material—development of homogeneous catalysts for selective hydrogen release. Chem. Soc. Rev. 45, 3954–3988 (2016).

    CAS  Article  Google Scholar 

  36. 36.

    Yu, X. & Pickup, P. G. Recent advances in direct formic acid fuel cells (DFAFC). J. Power Sources 182, 124–132 (2008).

    CAS  Article  Google Scholar 

  37. 37.

    Li, H. et al. Integrated electromicrobial conversion of CO2 to higher alcohols. Science 335, 1596–1596 (2012).

    CAS  Article  Google Scholar 

  38. 38.

    Loges, B., Boddien, A., Gärtner, F., Junge, H. & Beller, M. Catalytic generation of hydrogen from formic acid and its derivatives: useful hydrogen storage materials. Top. Catal. 53, 902–914 (2010).

    CAS  Article  Google Scholar 

  39. 39.

    Guo, Z. et al. Highly efficient and selective photocatalytic CO2 reduction by iron and cobalt quaterpyridine complexes. J. Am. Chem. Soc. 138, 9413–9416 (2016).

    CAS  Article  Google Scholar 

  40. 40.

    Matsuoka, S. et al. Efficient and selective electron mediation of cobalt complexes with cyclam and related macrocycles in the p-terphenyl-catalyzed photoreduction of carbon dioxide. J. Am. Chem. Soc. 115, 601–609 (1993).

    CAS  Article  Google Scholar 

  41. 41.

    Jeoung, J.-H. & Dobbek, H. Carbon dioxide activation at the Ni,Fe-cluster of anaerobic carbon monoxide dehydrogenase. Science 318, 1461–1464 (2007).

    CAS  Article  Google Scholar 

  42. 42.

    Appel, A. M. et al. Frontiers, opportunities and challenges in biochemical and chemical catalysis of CO2 fixation. Chem. Rev. 113, 6621–6658 (2013).

    CAS  Article  Google Scholar 

  43. 43.

    Wang, J.-W., Zhong, D.-C. & Lu, T.-B. Artificial photosynthesis: catalytic water oxidation and CO2 reduction by dinuclear non-noble-metal molecular catalysts. Coord. Chem. Rev. 377, 225–236 (2018).

    CAS  Article  Google Scholar 

  44. 44.

    Ouyang, T., Huang, H.-H., Wang, J.-W., Zhong, D.-C. & Lu, T.-B. A dinuclear cobalt cryptate as a homogeneous photocatalyst for highly selective and efficient visible-light driven CO2 reduction to CO in CH3CN/H2O solution. Angew. Chem. Int. Ed. 56, 738–743 (2017).

    CAS  Article  Google Scholar 

  45. 45.

    Ouyang, T. et al. Dinuclear metal synergistic catalysis boosts photochemical CO2-to-CO conversion. Angew. Chem. Int. Ed. 57, 16480–16485 (2018).

    CAS  Article  Google Scholar 

  46. 46.

    Taheri, A., Thompson, E. J., Fettinger, J. C. & Berben, L. A. An iron electrocatalyst for selective reduction of CO2 to formate in water: including thermochemical insights. ACS Catal. 5, 7140–7151 (2015).

    CAS  Article  Google Scholar 

  47. 47.

    Paul, A., Connolly, D., Schulz, M., Pryce, M. T. & Vos, J. G. Effect of water during the quantitation of formate in photocatalytic studies on CO2 reduction in dimethylformamide. Inorg. Chem. 51, 1977–1979 (2012).

    CAS  Article  Google Scholar 

  48. 48.

    Kuramochi, Y., Kamiya, M. & Ishida, H. Photocatalytic CO2 reduction in N,N-dimethylacetamide/water as an alternative solvent system. Inorg. Chem. 53, 3326–3332 (2014).

    CAS  Article  Google Scholar 

  49. 49.

    Du, Y. et al. Strongly reducing, visible-light organic photoredox catalysts as sustainable alternatives to precious metals. Chem. Eur. J. 23, 10962–10968 (2017).

    CAS  Article  Google Scholar 

  50. 50.

    Fang, Y. & Wang, X. Photocatalytic CO2 conversion by polymeric carbon nitrides. Chem. Commun. 54, 5674–5687 (2018).

    CAS  Article  Google Scholar 

  51. 51.

    Wang, X. et al. A metal-free polymeric photocatalyst for hydrogen production from water under visible light. Nat. Mater. 8, 76–80 (2008).

    Article  Google Scholar 

  52. 52.

    Maeda, K., Sekizawa, K. & Ishitani, O. A polymeric-semiconductor–metal-complex hybrid photocatalyst for visible-light CO2 reduction. Chem. Commun. 49, 10127–10129 (2013).

    CAS  Article  Google Scholar 

  53. 53.

    Cometto, C. et al. Highly selective molecular catalysts for the CO2-to-CO electrochemical conversion at very low overpotential. Contrasting Fe vs Co quaterpyridine complexes upon mechanistic studies. ACS Catal. 8, 3411–3417 (2018).

    CAS  Article  Google Scholar 

  54. 54.

    Wang, M., Chen, L., Lau, T.-C. & Robert, M. A hybrid Co quaterpyridine complex/carbon nanotube catalytic material for CO2 reduction in water. Angew. Chem. Int. Ed. 57, 7769–7773 (2018).

    CAS  Article  Google Scholar 

  55. 55.

    Cometto, C. et al. Molecular electrochemical catalysis of the CO2-to-CO conversion with a Co complex: a cyclic voltammetry mechanistic investigation. Organometallics (2018).

    Article  Google Scholar 

  56. 56.

    Kesharwani, M. K., Brauer, B. & Martin, J. M. L. Frequency and zero-point vibrational energy scale factors for double-hybrid density functionals (and other selected methods): can anharmonic force fields be avoided? J. Phys. Chem. A 119, 1701–1714 (2015).

    CAS  Article  Google Scholar 

  57. 57.

    Palmer, R. A. & Piper, T. S. 2,2’-Bipyridine complexes. I. Polarized crystal spectra of tris (2,2’-bipyridine)copper(ii), -nickel(ii), -cobalt(ii), -iron(ii) and -ruthenium(ii). Inorg. Chem. 5, 864–878 (1966).

    CAS  Article  Google Scholar 

  58. 58.

    Martha, S., Nashim, A. & Parida, K. M. Facile synthesis of highly active g-C3N4 for efficient hydrogen production under visible light. J. Mater. Chem. A 1, 7816–7824 (2013).

    CAS  Article  Google Scholar 

  59. 59.

    Lee, I.-S. H., Jeoung, E. H. & Kreevoy, M. M. Marcus theory of a parallel effect on α for hydride transfer reaction between NAD+ analogues. J. Am. Chem. Soc. 119, 2722–2728 (1997).

    CAS  Article  Google Scholar 

  60. 60.

    Stefankiewicz, A. R. et al. Self-assembly of transition metal ion complexes of a hybrid pyrazine-terpyridine ligand. Dalton Trans. 42, 1743–1751 (2013).

    CAS  Article  Google Scholar 

  61. 61.

    Okamura, R., Wada, T., Aikawa, K., Nagata, T. & Tanaka, K. A platinum−ruthenium dinuclear complex bridged by bis(terpyridyl)xanthene. Inorg. Chem. 43, 7210–7217 (2004).

    CAS  Article  Google Scholar 

  62. 62.

    Pearson, R. M., Lim, C.-H., McCarthy, B. G., Musgrave, C. B. & Miyake, G. M. Organocatalyzed atom transfer radical polymerization using N-aryl phenoxazines as photoredox catalysts. J. Am. Chem. Soc. 138, 11399–11407 (2016).

    CAS  Article  Google Scholar 

  63. 63.

    Frisch. M. J. et al. Gaussian 09, Revision A.02 (Gaussian, 2016).

  64. 64.

    Miertus, S., Scrocco, E. & Tomasi, J. Electrostatic interaction of a solute with a continuum. A direct utilizaion of AB initio molecular potentials for the prevision of solvent effects. Chem. Phys. 55, 117–129 (1981).

    CAS  Article  Google Scholar 

  65. 65.

    Miertus, S. & Tomasi, J. Approximate evaluations of the electrostatic free energy and internal energy changes in solution processes. Chem. Phys. 65, 239–245 (1982).

    CAS  Article  Google Scholar 

  66. 66.

    Tawa, G. J., Topol, I. A., Burt, S. K., Caldwell, R. A. & Rashin, A. A. J. Calculation of the aqueous solvation free energy of the proton. Chem. Phys. 109, 4852–4863 (1998).

    CAS  Google Scholar 

  67. 67.

    Kelly, C. P., Cramer, C. J. & Truhlar, D. G. Single-ion solvation free energies and the normal hydrogen electrode potential in methanol, acetonitrile, and dimethyl sulfoxide. J. Phys. Chem. B 111, 408–422 (2007).

    CAS  Article  Google Scholar 

Download references


The work described in this project was supported by the National Science Foundation of China (grant no. 21703034), Hong Kong University Grants Committee Area of Excellence Scheme (grant no. AoE/P-03–08), Hong Kong Research Grants Council (N_CityU115/18) and the French National Agency for Research (ANR-16-CE05-0010-01). G.C. acknowledges start-up grants from Dongguan University of Technology for high-level talents (grant nos G200906-47, GC200109-17 and KCYKYQD2017016). K.C.L. and M.R. acknowledge partial financial support from CityU Strategic Research Grant no. 7004819 and from the Institut Universitaire de France (IUF), respectively. PhD fellowships to C.C. from Université Sorbonne Paris Cité (USPC) and to B.M. from the China Scholarship Council (CSC student no. 201707040042) are acknowledged. G. Thoraval (Université Paris Diderot) is thanked for the design and preparation of the glassy carbon electrode (3 mm diameter) used during CV experiments. Finally, we thank G. Miyake (Colorado State University) for the sample gift of phenoxazine (Pheno).

Author information




G.C., K.-C.L., M.R. and T.-C.L. conceived and supervised the project. G.C., L.C. and H.F. designed and synthesized the catalysts. W.-L.M. and S.-M.Y. characterized the structure of catalyst 1. Z.G., C.C. and B.M. carried out the CO2 reduction experiments. C.C. performed the spectro-electrochemistry experiments. H.Z. and T.G. carried out the DFT calculations. All authors discussed the results and assisted during manuscript preparation.

Corresponding authors

Correspondence to Kai-Chung Lau, Tai-Chu Lau or Marc Robert.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary methods, Supplementary Figs. 1–30, Supplementary Tables 1–8, Supplementary references

Compound 1

Crystallographic data for compound 1.

Supplementary Data File

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Guo, Z., Chen, G., Cometto, C. et al. Selectivity control of CO versus HCOO production in the visible-light-driven catalytic reduction of CO2 with two cooperative metal sites. Nat Catal 2, 801–808 (2019).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing