(292g) Diffusion in Nanoporous Materials: Challenges, Surprises and Tasks of the Day

Jörg Kärger

Faculty of Physics and Earth Sciences, Leipzig University, 04103 Leipzig, Linnéstraße 5, Germany,

kaerger@physik.uni-leipzig.de

Nanoporous materials are in the heart of numerous technologies of matter upgrading by mass separation and conversion, given the intimate interaction between the guest molecules and the internal surface of the host material. „Microporous” materials with pore diameters matching the dimension of the molecules offer particularly favorable conditions. Their performance, however, is impeded by the diffusional resistance in such materials since the exchange rate with the surrounding atmosphere limits the gain in value-added products. A powerful way out of this dilemma is provided by the use of „hierarchically” porous materials. Here, the microporous space is permeated by mesopores, ensuring both the elementary processes of matter upgrading (in the micropores) and sufficiently fast matter exchange (via the mesopores). The complexity of such systems and the multitude of parameters of influence on overall mass transfer [1,2] make diffusion measurement a challenging task, by far more complicated than with the purely microporous material. „Microscopic” techniques of diffusion measurement like pulsed field gradient NMR and microimaging by IR and interference microscopy [3] shall be shown to be particularly suitable for such studies. It was mainly this type of measurement which, in the past, gave rise to a paradigm shift in our understanding, stimulating the formation of an IUPAC research group aiming to establish a “first comprehensive set of guidelines for measuring and reporting diffusivities in nanoporous materials” [4]. The talk reports about current developments and surprises of this initiative, highlighting Stefano Brandani’s landmark contributions [5-8].

References

[1] S. Hwang, J. Haase, E. Miersemann, and J. Kärger, Adv. Mater. Interfaces 8 (2021) 2000749.

[2] S. Hwang, J. Kärger, and E. Miersemann, Adsorption 27 (2021) 761–776.

[3] J. Kärger, and D.M. Ruthven, New J. Chem. 40 (2016) 4027–4048.

[4] J. Kärger, D.M. Ruthven, and R. Valiullin, Adsorption 27 (2021) 265–266 and Chemistry International 43 (2021) 25–29.

[5] S. Brandani, Adsorption 27 (2021) 353–368.

[6] S. Brandani, and E. Mangano, Adsorption 27 (2021) 319–351.

[7] D.M. Ruthven, J. Kärger, S. Brandani, and E. Mangano, Adsorption 27 (2021) 787–799.

[8] J.-Y. Wang, E. Mangano, S. Brandani, and D.M. Ruthven, Adsorption 27 (2021) 295–318.