Understanding the effect of host flexibility on the adsorption of CH₄, CO₂ and SF₆ in porous organic cages

Yang, Siyuan, Chen, Linjiang, Holden, Daniel, Wang, Ruiyao, Cheng, Yuanyuan, Wells, Mona, Cooper, Andrew I ORCID: 0000-0003-0201-1021 and Ding, Lifeng (2019) Understanding the effect of host flexibility on the adsorption of CH₄, CO₂ and SF₆ in porous organic cages. ZEITSCHRIFT FUR KRISTALLOGRAPHIE-CRYSTALLINE MATERIALS, 234 (7-8). pp. 547-555.

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Abstract

<jats:title>Abstract</jats:title> <jats:p>Molecular simulations for gas adsorption in microporous materials with flexible host structures is challenging and, hence, relatively rare. To date, most gas adsorption simulations have been carried out using the grand-canonical Monte Carlo (GCMC) method, which fundamentally does not allow the structural flexibility of the host to be accounted for. As a result, GCMC simulations preclude investigation into the effect of host flexibility on gas adsorption. On the other hand, approaches such as molecular dynamics (MD) that simulate the dynamic evolution of a system almost always require a fixed number of particles in the simulation box. Here we use a hybrid GCMC/MD scheme to include host flexibility in gas adsorption simulations. We study the adsorption of three gases – CH<jats:sub>4</jats:sub>, CO<jats:sub>2</jats:sub> and SF<jats:sub>6</jats:sub> – in the crystal of a porous organic cage (POC) molecule, CC3-R, whose structural flexibility is known by experiment to play an important role in adsorption of large guest molecules [L. Chen, P. S. Reiss, S. Y. Chong, D. Holden, K. E. Jelfs, T. Hasell, M. A. Little, A. Kewley, M. E. Briggs, A. Stephenson, K. Mark Thomas, J. A. Armstrong, J. Bell, J. Busto, R. Noel, J. Liu, D. M. Strachan, P. K. Thallapally, A. I. Cooper, Separation of rare gases and chiral molecules by selective binding in porous organic cages. <jats:italic>Nat. Mater.</jats:italic> <jats:bold>2014</jats:bold>, <jats:italic>13</jats:italic>, 954, D. Holden, S. Y. Chong, L. Chen, K. E. Jelfs, T. Hasell, A. I. Cooper, Understanding static, dynamic and cooperative porosity in molecular materials. <jats:italic>Chem. Sci.</jats:italic> <jats:bold>2016</jats:bold>, <jats:italic>7</jats:italic>, 4875]. The results suggest that hybrid GCMC/MD simulations can reproduce experimental adsorption results, without the need to adjust the host–guest interactions in an <jats:italic>ad hoc</jats:italic> way. Negligible errors in adsorption capacity and isosteric heat are observed with the rigid-host assumption for small gas molecules such as CH<jats:sub>4</jats:sub> and CO<jats:sub>2</jats:sub> in CC3-R, but the adsorption capacity of the larger SF<jats:sub>6</jats:sub> molecule in CC3-R is hugely underestimated if flexibility is ignored. By contrast, hybrid GCMC/MD adsorption simulations of SF<jats:sub>6</jats:sub> in CC3-R can accurately reproduce experiment. This work also provides a molecular level understanding of the cooperative adsorption mechanism of SF<jats:sub>6</jats:sub> in the CC3-R molecular crystal.</jats:p>

Item Type:	Article
Uncontrolled Keywords:	gas adsorption, molecular simulation, organic molecular crystals, porous organic cages
Depositing User:	Symplectic Admin
Date Deposited:	02 Mar 2020 15:30
Last Modified:	14 Oct 2023 09:35
DOI:	10.1515/zkri-2018-2150
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3077452