(532du) Analysis and Augmentation of Guest-Host Interaction Energy Models As CHA and AEI Zeolite Crystallization Phase Predictors
AIChE Annual Meeting
Wednesday, November 16, 2022 - 3:30pm to 5:00pm
Chabazite (CHA) and AEI are cage-window zeolites that share the same double six ring (d6r) secondary building unit arranged in different stackings. Structurally similar organic structure directing agents (OSDAs) are observed to promote crystallization of one phase over the other. These differences are not captured faithfully by reported guest-host interaction energies (GHIE) between a templating molecule and the siliceous framework. Here we explore both the energetics and dynamics of void occlusion of a series of OSDAs across CHA and AEI, using discrete configurational sampling combined with density functional theory energy models, and classical molecular dynamics combined with conventional standard forcefields. We find that all methods report similar trends in GHIE and similarly fail to predict observed crystallization tendencies. From analysis of discrete sampling and molecular dynamics, we observe differences in the abilities of OSDAs to fill cages even among OSDAs of similar GHIE, suggesting some intrinsic OSDA shape feature as a secondary descriptor. By screening over a set of common molecular descriptors, we find that GHIE combined with molecular eccentricity or asymmetry is able to correctly predict crystallization tendencies between CHA and AEI. The results point to strategies for leveraging GHIE calculations to identify secondary OSDA features useful for predicting crystallization patterns.