Probing the Spaces of Microporous Materials for Enhanced Molecular Accessibility and Catalytic Control

The confining environment of microporous materials provide additional control for modifying the energetics of adsorbed species and the accessibility of reactants and products. However, small changes in molecular size and structure comparable to the pore or window size of the selected porous material yield large changes in molecular behavior^[1]. In this work, the accessibility, adsorption, and transport of hydrocarbons are described using in situ characterization of the position of tunable adsorbing amines with time. Prediction of molecular sieving via three methods of describing rigid molecular size are directly compared with experimentally-measured molecular accessibility obtained via both reactive gas chromatography and in situ infrared spectroscopy^[2]. These results are expanded to permit characterization of the different transport time scales of hierarchical microporous materials.

[1] P.J. Dauenhauer, Omar Abdelrahman, “A Universal Descriptor for the Entropy of Adsorbed Molecules in Confined Spaces,” ACS Central Science 2018, 4(9), 1235-1243. DOI: 10.1021/acscentsci.8b00419

[2] Omar A. Abdelrahman, K.P. Vinter, L. Ren, D.Xu, R.J. Gorte, M. Tsapatsis, P.J. Dauenhauer, “Simple Quantification of Zeolite Acid Site Density by Reactive Gas Chromatography,” Catalysis Science & Technology 2017, 7, 3831-3841. DOI: 10.1039/C7CY01068K

[3] Y. Guefrachi, G. Sharma, D. Xu, G. Kumar, K.P. Vinter, O.A. Abdelrahman, S.A. Hassan, P.J. Dauenhauer, A. Navrotsky, W. Zhang, M. Tsapatsis, "Steam-Induced Coarsening of Single-Unit-Cell MFI Zeolite Nanosheets and its Effect on External Surface Bronsted Acid Catalysis," Angewandte Chemie International Edition 2020, DOI: 10.1002/anie.202000395