title: CO2adsorption-induced structural changes in coordination polymer ligands elucidated via molecular simulations and experiments.
abstract: Aiming to elucidate guest-induced structural changes in the coordination polymer CPL-2, grand canonical Monte Carlo (GCMC) simulations were used to predict CO2loadings in this material, and the results were compared with experimental isotherms. Our calculations suggest that CPL-2 exhibits more pronounced CO2-induced structural changes than previously reported. As the initial evidence, the isotherm simulated in the previously reported CPL-2 structure (experimentally resolved from X-ray diffraction in the "as-synthesized" CPL-2) underestimated the measured CO2loadings at high pressure, indicating that CPL-2 might undergo structural changes that enable higher pore volumes at high pressure. GCMC simulations in CPL-2 structures considering moderate unit cell expansions reported in the literature still underestimated high-pressure experimental loadings. However, considering an incremental rotation of the CPL-2 bipyridyl pillars with increasing CO2pressure, we were able to trace the measured isotherm with the simulation data. Computational analysis shows that ligand rotation in CPL-2 enables higher pore volumes, which, in turn, accommodate more CO2as the gas pressure increases. Desorption measurements suggest that hysteresis in the CO2isotherm of CPL-2 may also be linked to ligand rotation, and the measured adsorption/desorption cycles show that the rotation is reversible. Based on our simulations for CPL-4 and CPL-5 and previously reported experimental data, it is likely that these materials, which differ from CPL-2 in the bipyridyl ligand, behave similarly in the presence of CO2. Our results help understand the behavior of these materials, which present the kind of structural changes that could be potentially exploited to enhance the CO2working capacity of ultra-microporous materials for carbon capture applications.
authors.affiliation: Department of Chemical Engineering, University of Puerto Rico - Mayaguez Campus, Road 108 - km 1.1, Mayaguez, PR 00681-9000, Puerto Rico. maria.curetarana@upr.edu.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Meza-Morales
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.
authors.forename: Diego A
authors.initials: DA
authors.lastname: Gómez-Gualdrón
authors.affiliation: Department of Chemical Engineering, University of Puerto Rico - Mayaguez Campus, Road 108 - km 1.1, Mayaguez, PR 00681-9000, Puerto Rico. maria.curetarana@upr.edu.
authors.forename: Rodinson R
authors.initials: RR
authors.lastname: Arrieta-Perez
authors.affiliation: Department of Chemical Engineering, University of Puerto Rico - Mayaguez Campus, Road 108 - km 1.1, Mayaguez, PR 00681-9000, Puerto Rico. maria.curetarana@upr.edu.
authors.forename: Arturo J
authors.identifier: http://orcid.org/0000-0001-9379-8987
authors.initials: AJ
authors.lastname: Hernández-Maldonado
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.
authors.forename: Randall Q
authors.identifier: http://orcid.org/0000-0003-2925-9246
authors.initials: RQ
authors.lastname: Snurr
authors.affiliation: Department of Chemical Engineering, University of Puerto Rico - Mayaguez Campus, Road 108 - km 1.1, Mayaguez, PR 00681-9000, Puerto Rico. maria.curetarana@upr.edu.
authors.forename: María C
authors.initials: MC
authors.lastname: Curet-Arana