Gas Storage and Separation in Porous Frameworks

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Porous frameworks, such as metal–organic frameworks, hold small molecules inside pores only a few ångströms wide. By choosing the size and chemistry of those pores, a framework can be made to store a gas or to take up one gas and reject another, which makes these materials candidates for capturing CO2, separating air and hydrocarbons, and storing hydrogen at moderate pressures. Our first-principles calculations, working alongside adsorption, diffraction and spectroscopy measurements by our collaborators, show where the molecules bind and why a framework prefers one gas over another.

Much of our recent work concerns aluminum formate, Al(HCOO)3 or ALF, a framework made cheaply from commodity chemicals. ALF removes CO2 from N2-rich gas streams by a size-selective separation that rests on the small difference between the two molecules’ kinetic diameters,[1] and its hydrogen-lined pore cavities recognize CO2 while rejecting hydrocarbons, including acetylene and methane.[2] The same material adsorbs O2 from air near dry-ice temperatures, without cryogenic distillation,[3] and stores hydrogen competitively at 120–160 K and 10–20 bar.[4] We have also traced its temperature-regulated gating, which lets temperature alone switch the separation of one gas from another, to the motion of the formate linkers that frame the windows between its cavities.[5]

This builds on our earlier first-principles work on metal–organic frameworks, from the diffusion of small molecules through their channels[6] to high-throughput screening of small-molecule adsorption.[7]

Relevant references

  1. Evans H. A., Mullangi D., Deng Z., Wang Y., Peh S. B., Wei F., Wang J., Brown C. M., Zhao D., Canepa P., and Cheetham A. K.; Sci. Adv. 8, eade1473 (2022)
  2. Zhang Z., Deng Z., Evans H. A., Mullangi D., Kang C., Bo Peh S., Wang Y., Brown C. M., Wang J., Canepa P., Cheetham A., and Zhao D.; J. Am. Chem. Soc. 145, 11643 (2023)
  3. Mullangi D., Evans H. A., Yildirim T., Wang Y., Deng Z., Zhang Z., Mai T. T., Wei F., Wang J., Hight Walker A. R., Brown C. M., Zhao D., Canepa P., and Cheetham A.; J. Am. Chem. Soc. 145, 9850 (2023)
  4. Evans H. A., Yildirim T., Peng P., Cheng Y., Deng Z., Zhang Q., Mullangi D., Zhao D., Canepa P., Breunig H. M., Cheetham A. K., and Brown C. M.; J. Am. Chem. Soc. 145, 22150 (2023)
  5. Evans H. A., Yildirim T., McCarver G. A., Mai T. T., Cheng Y., Deng Z., Klein R. A., Zhao D., Canepa P., Hight Walker A. R., Cheetham A. K., and Brown C. M.; Chem. Mater. 37, 7102–7114 (2025)
  6. Canepa P., Nijem N., Chabal Y. J., and Thonhauser T.; Phys. Rev. Lett. 110, 026102 (2013)
  7. Canepa P., Arter C. A., Conwill E. M., Johnson D. H., Shoemaker B. A., Soliman K. Z., and Thonhauser T.; J. Mater. Chem. A 1, 13597–13604 (2013)