Chemical and Biomolecular Engineering
Faculty Advisor: Yamil Colón
Computational Materials Discovery and Design for Water Vapor Adsorption using Nanoporous Materials
Water is necessary for energy production due to its low-cost, high availability, and ease of use in the energy generation processes. It is also used as a medium for exchanging heat, for generating energy (via steam), for cleaning equipment, as well as for human consumption. However, water is not an unlimited resource and due to climate change, increase in energy demand, and rising global population, it is becoming scarce and unavailable to many parts of the world . A solution to mitigate water scarcity is to devise novel technologies for recovering water vapor directly from air as well as from waste streams exiting from various industries. This extracted water vapor can be recycled back to the industrial and public facilities, and for this prospect, nanoporous materials such as metal-organic frameworks (MOFs) can offer a reliable, and tailored solution . MOFs have the highest surface area per volume among all the crystalline materials, and many of them have demonstrated wide applicability in energy storage and separations including their use as atmospheric water harvester (AWH) materials [3,4]. My project aims to develop a computational method to study water vapor adsorption and separations in MOFs and determine how design variables such as pore size, geometry, electrostatics, and different functional groups affect the adsorption and separation mechanism. My Ph.D. project will leverage the established criteria to inform the rational design and discovery of porous materials for water vapor adsorption and separation.
Our preliminary results on water vapor interaction with idealized carbon cylinders (ICC) suggests that relative humidity (vapor pressure) has a significant role in affecting the adsorption phenomena. I found that the water vapor uptake in adsorption isotherm quickly rose to its highest water vapor uptake capacity beyond a pressure point, which signifies the presence of a limiting pressure after which the surface becomes hydrophilic. This study also confirms that charge arrangement on pore surface has a significant influence in influencing the hydrophilicity of ICCs. For example, the surface was found to be more hydrophilic when charges are alternated (from positive to negative) along the vertical axis (directed parallel to the pore length), then when they were alternated along the horizontal axis (perpendicular to the pore length). Electric potential maps and water vapor density isotherm for these cylinders further confirmed that charge arrangement plays a very important role in determining the hydrophilicity of these surfaces. We hypothesize that MOFs having similar electrostatic characteristics to the ICCs would also exhibit identical water vapor adsorption behavior and they can be potentially used for AWH technology and other water vapor separation processes. Further, novel MOFs may be designed by adding chemical moieties to existing MOFs to induce a desired water vapor adsorption and separation behavior as observed in the ICCs. In the next phase, I plan to develop an entropy-biasing Monte Carlo algorithm, since modeling of water vapor adsorption with MOFs has proven to be difficult due to large equilibration time and slow convergence rate. With the current MC algorithm, it is nearly impossible to simulate hypothetical structures from MOF databases such as inorganic crystal structure database (ICSD) and the Cambridge structural database (CSD). After developing this protocol, I wish to conduct a high-throughput screening to find the best performing MOFs for water vapor adsorption and separation applications.
(1) Richey, A. S., Thomas, B. F., Lo, M.‐H., Reager, J. T., Famiglietti, J. S., Voss, K., Swenson, S., and Rodell, M.( 2015), Quantifying renewable groundwater stress with GRACE, Water Resour. Res., 51, 5217– 5238
(2) J. Canivet, A. Fateeva, Y. Guo, B. Coasne, D. Farrusseng, Water adsorption in MOFs: Fundamentals and applications. Chemical Society Reviews. 43 (2014), pp. 5594–5617
(3) Matthew W. Logan, Spencer Langevin & Zhiyong Xia, Reversible Atmospheric Water Harvesting Using Metal-Organic Frameworks. Scientific Reports. 10 (2020), Article number: 1492
(4) Kim, Hyunho, A Yang, Sungwoo, A Rao, Sameer R., A Narayanan, Shankar, A Kapustin, Eugene A, A Furukawa, Hiroyasu, A Umans, Ari S, A Yaghi, Omar M. A Wang, Evelyn N. Water harvesting from air with metal-organic frameworks powered by natural sunlight, Science, 430-434