Direct air capture of CO2 via aqueous-phase absorption and crystalline-phase release using concentrated solar power


Using negative emissions technologies for the net removal of greenhouse gases from the atmosphere could provide a pathway to limit global temperature rises. Direct air capture of carbon dioxide offers the prospect of permanently lowering the atmospheric CO2 concentration, providing that economical and energy-efficient technologies can be developed and deployed on a large scale. Here, we report an approach to direct air capture, at the laboratory scale, using mostly off-the-shelf materials and equipment. First, CO2 absorption is achieved with readily available and environmentally friendly aqueous amino acid solutions (glycine and sarcosine) using a household humidifier. The CO2-loaded solutions are then reacted with a simple guanidine compound, which crystallizes as a very insoluble carbonate salt and regenerates the amino acid sorbent. Finally, effective CO2 release and near-quantitative regeneration of the guanidine compound are achieved by relatively mild heating of the carbonate crystals using concentrated solar power.

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Fig. 1: CO2 capture from ambient air with PyBIG.
Fig. 2
Fig. 3: Representative CO2-loading curves for aqueous amino acid solutions.
Fig. 4: Amino acid regeneration.


  1. 1.

    Trends in Atmospheric Carbon Dioxide (Earth System Research Laboratory, Global Monitoring Division, NOAA, accessed September 2017);

  2. 2.

    Blunden, J. & Arndt, D. S. (eds) State of the climate in 2016. Bull. Am. Meteor. Soc. 98, Si–S277 (2017).

    Article  Google Scholar 

  3. 3.

    Hansen, J. et al. Young people’s burden: requirement of negative CO2 emissions. Earth Syst. Dynam. 8, 577–616 (2017).

    Article  Google Scholar 

  4. 4.

    Gasser, T., Guivarch, C., Tachiiri, K., Jones, C. D. & Ciais, P. Negative emissions physically needed to keep global warming below 2 °C. Nat. Commun. 6, 7958 (2015).

  5. 5.

    Mauritsen, T. & Pincus, R. Committed warming inferred from observations. Nat. Clim. Change 7, 652–655 (2017).

  6. 6.

    Keith, D. W. Why capture CO2 from the atmosphere. Science 325, 1654–1655 (2009).

    Article  Google Scholar 

  7. 7.

    Lackner, K. S. et al. The urgency of the development of CO2 capture from ambient air. Proc. Natl Acad. Sci. USA 109, 13156–13162 (2012).

    Article  Google Scholar 

  8. 8.

    Sanz-Perez, E., Murdock, C. R., Didas, S. A. & Jones, C. W. Direct capture of CO2 from ambient air. Chem. Rev. 116, 11840–11876 (2016).

    Article  Google Scholar 

  9. 9.

    Smith, P. et al. Biophysical and economic limits to negative CO2 emissions. Nat. Clim. Change 6, 42–50 (2015).

  10. 10.

    Psarras, P. et al. Slicing the pie: How big could carbon dioxide removal be? WIREs Energy Environ. 6, e253 (2017).

    Article  Google Scholar 

  11. 11.

    Zeman, F. Energy and material balance of CO2 capture from ambient air. Environ. Sci. Technol. 41, 7558–7563 (2007).

    Article  Google Scholar 

  12. 12.

    Baciocchi, R., Storti, G. & Mazzotti, M. Process design and energy requirements for the capture of carbon dioxide from air. Chem. Eng. Process. 45, 1047–1058 (2006).

    Article  Google Scholar 

  13. 13.

    Stolaroff, J. K., Keith, D. W. & Lowry, G. V. Carbon dioxide capture from atmospheric air using sodium hydroxide spray. Environ. Sci. Technol. 42, 2728–2735 (2008).

    Article  Google Scholar 

  14. 14.

    Holmes, G. & Keith, D. W. An air–liquid contactor for large-scale capture of CO2 from air. Phil. Trans. R. Soc. A 370, 4380–4403 (2012).

    Article  Google Scholar 

  15. 15.

    Didas, S. A., Choi, S., Chaikittisilp, W. & Jones, C. W. Amine-oxide hybrid materials for CO2 capture from ambient air. Acc. Chem. Res. 48, 2680–2687 (2015).

    Article  Google Scholar 

  16. 16.

    Gebald, C., Wurzbacher, J. A., Tingaut, P., Zimmermann, T. & Steinfeld, A. Amine-based nanofibrillated cellulose as adsorbent for CO2 capture from air. Environ. Sci. Technol. 45, 9101–9108 (2011).

    Article  Google Scholar 

  17. 17.

    Goeppert, A. et al. Carbon dioxide capture from the air using a polyamine based regenerable solid adsorbent. J. Am. Chem. Soc. 133, 20164–20167 (2011).

    Article  Google Scholar 

  18. 18.

    McDonald, T. M. et al. Capture of carbon dioxide from air and flue gas in the alkylamine-appended metal-organic framework mmen-Mg2(dobpdc). J. Am. Chem. Soc. 134, 7056–7065 (2012).

    Article  Google Scholar 

  19. 19.

    Lu, W., Sculley, J. P., Yuan, D., Krishna, R. & Zhou, H.-C. Carbon dioxide capture from air using amine-grafted porous polymer networks. J. Phys. Chem. C. 117, 4057–4061 (2013).

    Article  Google Scholar 

  20. 20.

    Socolow, R. et al. Direct Air Capture of CO 2 with Chemicals. A Technology Assessment for the APS Panel on Public Affairs (American Physical Society, 2011).

  21. 21.

    Wang, T. et al. Characterization of kinetic limitations to atmospheric CO2 capture by solid sorbent. Greenh. Gas. Sci. Technol. 6, 138–149 (2016).

    Article  Google Scholar 

  22. 22.

    Wang, T., Lackner, K. S. & Wright, A. B. Moisture swing sorbent for carbon dioxide capture from ambient air. Environ. Sci. Technol. 45, 6670–6675 (2011).

    Article  Google Scholar 

  23. 23.

    Wang, T., Lackner, K. S. & Wright, A. B. Moisture-swing sorption for carbon dioxide capture from ambient air: A thermodynamic analysis. Phys. Chem. Chem. Phys. 15, 504–514 (2013).

    Article  Google Scholar 

  24. 24.

    Seipp, C. A., Williams, N. J., Kidder, M. K. & Custelcean, R. CO2 capture from ambient air by crystallization with a guanidine sorbent. Angew. Chem. Int. Ed. 56, 1042–1045 (2017).

    Article  Google Scholar 

  25. 25.

    Xiang, Q., Fang, M., Yu, H. & Maeder, M. Kinetics of the reversible reaction of CO2(aq) and HCO3 with sarcosine salt in aqueous solution. J. Phys. Chem. A. 116, 10276–10284 (2012).

    Article  Google Scholar 

  26. 26.

    Guo, D. et al. Amino acids as carbon capture solvents: Chemical kinetics and mechanism of the glycine + CO2 reaction. Energy Fuels 27, 3898–3904 (2013).

    Article  Google Scholar 

  27. 27.

    Shariff, A. M. & Shaikh, M. S. in Energy Efficient Solvents for CO 2 Capture by Gas-Liquid Absorption (ed. Budzianowski, W. M.) (Springer, Cham, 2017).

  28. 28.

    Carroll, J. J., Slupsky, J. D. & Mather, A. E. The solubility of carbon dioxide in water at low pressure. J. Phys. Chem. Ref. Data 20, 1201–1209 (1991).

    Article  Google Scholar 

  29. 29.

    Wang, X., Conway, W., Burns, R., McCann, N. & Maeder, M. Comprehensive study of the hydration and dehydration reactions of carbon dioxide in aqueous solutions. J. Phys. Chem. A 114, 1734–1740 (2010).

    Article  Google Scholar 

  30. 30.

    McCann, N., Maeder, M. & Hasse, H. A calorimetric study of carbamate formation. J. Chem. Thermodyn. 43, 664–669 (2011).

    Article  Google Scholar 

  31. 31.

    Hale, J. D., Izatt, R. M. & Christensen, J. J. A calorimetric study of the heat of ionization of water at 25 °. J. Phys. Chem. 67, 2605–2608 (1963).

    Article  Google Scholar 

  32. 32.

    Le Moullec, Y. & Neveux, T. in Absorption-Based Post-Combustion Capture of Carbon Dioxide (ed. Feron, P. H. M.), Woodhead Publishing Series in Energy: Number 101 (Elsevier, 2016).

  33. 33.

    Parikh, D. M. Vacuum drying: basics and application. Chem. Eng. 122, 48–54 (2015).

    Google Scholar 

  34. 34.

    Yang, N. et al. Protonation constants and thermodynamic properties of amino acid salts for CO2 capture at high temperature. Ind. Eng. Chem. Res. 53, 12848–12855 (2014).

    Article  Google Scholar 

  35. 35.

    Nikulshina, V., Gebald, C. & Steinfeld, A. CO2 capture from atmospheric air via consecutive CaO-carbonation and CaCO3-calcination cycles in a fluidized-bed solar reactor. Chem. Eng. J. 146, 244–248 (2009).

    Article  Google Scholar 

  36. 36.

    Sanchez Fernandez, E. et al. Conceptual design of a novel CO2 capture process based on precipitating amino acid solvents. Ind. Eng. Chem. Res. 52, 12223–12235 (2013).

    Article  Google Scholar 

  37. 37.

    Perry, R. J. et al. CO2 capture using phase-changing sorbents. Energy Fuels 26, 2528–2538 (2012).

    Article  Google Scholar 

  38. 38.

    Custelcean, R., Williams, N. J., Seipp, C. A., Ivanov, A. S. & Bryantsev, V. S. Aqueous sulfate separation by sequestration of [(SO4)2((H2O)4]4– clusters within highly insoluble imine-linked bis-guanidinium crystals. Chem. Eur. J. 22, 1997–2003 (2016).

    Article  Google Scholar 

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This research was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.

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F.M.B. performed and analysed the CO2 absorption and sorbent regeneration experiments, and the potentiometric titration measurements. N.J.W. optimized and scaled up the synthesis of PyBIG, optimized the CO2 absorption and sorbent regeneration with PyBIG, and performed the solubility measurements. C.A.S. designed and synthesized the PyBIG compound. M.K.K. performed and analysed the DSC and TGA measurements. R.C. led the project, conceptualized the study, performed the measurements with concentrated solar power and wrote the manuscript. All authors contributed to discussions and manuscript reviews.

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Correspondence to Radu Custelcean.

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Competing interests

A US patent application (no. 15/813,557), currently pending, has been filed, with R.C., C.A.S. and N.J.W. as inventors, covering the DAC system described in this manuscript.

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Supplementary Figures 1–12, Supplementary Tables 1–3 and Supplementary Methods

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Brethomé, F.M., Williams, N.J., Seipp, C.A. et al. Direct air capture of CO2 via aqueous-phase absorption and crystalline-phase release using concentrated solar power. Nat Energy 3, 553–559 (2018).

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