Adaptive Pore Opening to Form Tailored Adsorption Sites in a Cooperatively Flexible Framework Enables Record Inverse Propane/Propylene Separation

Published

October 11, 2023

Author(s)

Ryan Klein, Lukas Bingel, Arijit Halder, Marcus Carter, Benjamin Trump, Eric Bloch, Wei Zhou, Krista Walton, Craig Brown, C. McGuirk

Abstract

A proposed low-energy alternative to the separation of alkanes from alkenes by energy-intensive cryogenic distillation is separation by porous adsorbents. Unfortunately, most adsorbents preferentially take up the desired, high-value major component alkene, requiring frequent regeneration. Adsorbents with inverse selectivity for the minor component alkane would enable the direct production of purified, reagent-grade alkene, greatly reducing global energy consumption. However, such materials are exceedingly rare, especially for propane/propylene separation. Here, we report that through adaptive and spontaneous pore size and shape adaptation to optimize an ensemble of weak noncovalent interactions, the structurally responsive metal−organic framework CdIF-13 (sod−Cd(benzimidazolate)2) exhibits inverse selectivity for propane over propylene with record-setting separation performance under industrially relevant temperature, pressure, and mixture conditions. Powder synchrotron X-ray diffraction measurements combined with first-principles calculations yield atomicscale insight and reveal the induced fit mechanism of adsorbate-specific pore adaptation and ensemble interactions between ligands and adsorbates. Dynamic column breakthrough measurements confirm that CdIF-13 displays selectivity under mixed-component conditions of varying ratios, with a record measured selectivity factor of α ≈ 3 at 95:5 propylene:propane at 298 K and 1 bar. When sequenced with a low-cost rigid adsorbent, we demonstrated the direct purification of propylene under ambient conditions. This combined atomic-level structural characterization and performance testing firmly establishes how cooperatively flexible materials can be capable of unprecedented separation factors.

Citation

Journal of the American Chemical Society

Volume

145

Issue

40

Pub Type

Journals

Download Paper

https://doi.org/10.1021/jacs.3c06754

Local Download

Citation

Klein, R. , Bingel, L. , Halder, A. , Carter, M. , Trump, B. , Bloch, E. , Zhou, W. , Walton, K. , Brown, C. and McGuirk, C. (2023), Adaptive Pore Opening to Form Tailored Adsorption Sites in a Cooperatively Flexible Framework Enables Record Inverse Propane/Propylene Separation, Journal of the American Chemical Society, [online], https://doi.org/10.1021/jacs.3c06754, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936447 (Accessed October 10, 2025)