(529f) High-Throughput Screening of Alkane and Organophosphate Diffusion in Metal-Organic Frameworks
AIChE Annual Meeting
2020 Virtual AIChE Annual Meeting
Diffusion, Transport, and Dynamics in Adsorption Systems
Thursday, November 19, 2020 - 9:15am to 9:30am
Simulated diffusion coefficients of alkanes and organophosphates vary by orders of magnitude depending on MOF topology, even for the similar linker sizes used here. This is due in part to the Zr6 node connectivity, which can be 6-, 8-, or 12-connected to linkers. For topologies that are 12-connected, average diffusion coefficients of alkanes are lower at all adsorbate loadings relative to less-connected topologies, due to smaller average pore apertures. Average diffusion coefficients for both 6- and 8- connected topologies, however, do not differ from each other. The connectivity of the linkers does not significantly impact diffusivity. At high adsorbate fractional loading, diffusion coefficients correlate with pore size, but at low loadings, pore connectivity and pore shape control diffusion. For polar organophosphates, stronger adsorption to Zr6 nodes reduces diffusion at low adsorbate loadings, which are most relevant for CWA decomposition. We found that the choice of topology and linker were crucial to control organophosphate diffusion at low loadings, as diffusion coefficients vary by 3 orders of magnitude among topologies for structurally similar nodes and linkers. Coulombic interactions between nodes and adsorbates were shown to be dominant by removing node partial charges and comparing the distribution of adsorbates between frameworks with and without partial charges. We then extended these results to develop design rules for the diffusion of bulky polar adsorbates in other crystalline microporous materials.