@article{ritter_tudor_hogan_pham_space_2024, title={PHAHST Potential: Modeling Sorption in a Dispersion-Dominated Environment}, volume={6}, ISSN={["1549-9626"]}, url={https://doi.org/10.1021/acs.jctc.4c00226}, DOI={10.1021/acs.jctc.4c00226}, abstractNote={PHAHST (potentials with high accuracy, high speed, and transferability) is a recently developed force field that utilizes exponential repulsion, multiple dispersion terms, explicit many-body polarization, and many-body van der Waals interactions. The result is a systematic approach to force field development that is computationally practical. Here, PHAHST is employed in the simulation for rare gas uptake of krypton and xenon in the metal-organic material, HKUST-1. This material has shown promise in use as an adsorptive separating agent and presents a challenge to model due to the presence of heterogeneous interaction sorption surfaces, which include pores with readily accessible, open-metal sites that compete with dispersion-dominated pores. Such environments are difficult to simulate with commonly used empirical force fields, such as the Lennard-Jones (LJ) potential, which perform better when electrostatics are dominant in determining the nature of sorption and alone are incapable of modeling interactions with open-metal sites. The effectiveness of PHAHST is compared to the LJ potential in a series of mixed Kr-Xe gas simulations. It has been demonstrated that PHAHST compares favorably with experimental results, and the LJ potential is inadequate. Overall, we establish that force fields with physically grounded repulsion/dispersion terms are required in order to accurately model sorption, as these interactions are an important component of the energy. Furthermore, it is shown that the simple mixing rules work nearly quantitatively for the true pair potentials, while they are not transferable for effective potentials like LJ.}, journal={JOURNAL OF CHEMICAL THEORY AND COMPUTATION}, author={Ritter, Logan and Tudor, Brant and Hogan, Adam and Pham, Tony and Space, Brian}, year={2024}, month={Jun} }
 @article{mohamed_elzeny_samuel_huang_helal_galanek_xu_kim_pham_miller_et al._2024, title={Trailblazing Kr/Xe Separation: The Birth of the First Kr-Selective Material}, volume={4}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.4c01833}, abstractNote={Efficient separation of Kr from Kr/Xe mixtures is pivotal in nuclear waste management and dark matter research. Thus far, scientists have encountered a formidable challenge: the absence of a material with the ability to selectively adsorb Kr over Xe at room temperature. This study presents a groundbreaking transformation of the renowned metal–organic framework (MOF) CuBTC, previously acknowledged for its Xe adsorption affinity, into an unparalleled Kr-selective adsorbent. This achievement stems from an innovative densification approach involving systematic compression of the MOF, where the crystal size, interparticle interaction, defects, and evacuation conditions are synergistically modulated. The resultant densified CuBTC phase exhibits exceptional mechanical resilience, radiation tolerance, and notably an unprecedented selectivity for Kr over Xe at room temperature. Simulation and experimental kinetic diffusion studies confirm reduced gas diffusion in the densified MOF, attributed to its small pore window and minimal interparticle voids. The lighter Kr element demonstrates facile surface passage and higher diffusivity within the material, while the heavier Xe encounters increased difficulty entering the material and lower diffusivity. This Kr-selective MOF not only represents a significant breakthrough in Kr separation but also demonstrates remarkable processability and scalability to kilogram levels. The findings presented herein underscore the transformative potential of engineered MOFs in addressing complex challenges, heralding a new era of Kr separation technologies.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Mohamed, Mona H. and Elzeny, Islam and Samuel, Joshua and Huang, Yimeng and Helal, Ahmed S. and Galanek, Mitchell and Xu, Wenqian and Kim, So Yeon and Pham, Tony and Miller, Lenore and et al.}, year={2024}, month={Apr} }
 @article{mohamed_elzeny_samuel_xu_malliakas_picard_pham_miller_hogan_space_et al._2024, title={Turning Normal to Abnormal: Reversing CO<sub>2</sub>/C2-Hydrocarbon Selectivity in HKUST-1}, volume={1}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202312280}, abstractNote={Abstract}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Mohamed, Mona H. and Elzeny, Islam and Samuel, Joshua and Xu, Wenqian and Malliakas, Christos D. and Picard, Yoosuf N. and Pham, Tony and Miller, Lenore and Hogan, Adam and Space, Brian and et al.}, year={2024}, month={Jan} }
 @article{forrest_pham_chen_jiang_madden_franz_hogan_zaworotko_space_2021, title={Tuning the Selectivity between C2H2 and CO2 in Molecular Porous Materials}, volume={37}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.1c02009}, abstractNote={A combined experimental and theoretical study of C2H2 and CO2 adsorption and separation was performed in two isostructural molecular porous materials (MPMs): MPM-1-Cl ([Cu2(adenine)4Cl2]Cl2) and MPM-1-TIFSIX ([Cu2(adenine)4(TiF6)2]). It was revealed that MPM-1-Cl displayed higher low-pressure uptake, isosteric heat of adsorption (Qst), and selectivity for C2H2 than CO2, whereas the opposite was observed for MPM-1-TIFSIX. While MPM-1-Cl contains only one type of accessible channel, which has a greater preference toward C2H2, MPM-1-TIFSIX contains three distinct accessible channels, one of which is a confined region between two large channels that represents the primary binding site for both adsorbates. According to molecular simulations, the initial adsorption site in MPM-1-TIFSIX interacts more strongly with CO2 than C2H2, thus explaining the inversion of adsorbate selectivity relative to MPM-1-Cl.}, number={47}, journal={LANGMUIR}, author={Forrest, Katherine A. and Pham, Tony and Chen, Kai-Jie and Jiang, Xue and Madden, David G. and Franz, Douglas M. and Hogan, Adam and Zaworotko, Michael J. and Space, Brian}, year={2021}, month={Nov}, pages={13838–13845} }