(4bz) From Molecular Simulations to Gas Separation/Storage Applications

Recently, nano-porous materials such as zeolites and metal organic frameworks (MOFs) have been shown to potentially provide a more energy-efficient way for gas separation and storage applications.  A huge number of material candidates can be possibly achieved by tuning both structural topologies and chemical compositions. Fully characterizing all those materials with experimental methods is therefore prohibitive. To identify promising materials, computational study plays a crucial role by utilizing various techniques in molecular simulations.

Accordingly, we have performed several large-scale computational screenings of hundred thousand structures on the basis of adsorption or membrane processes for several applications, including carbon dioxide capture, methane capture/storage, and olefin/paraffin separation. From the outcomes of these large-scale screenings, a number of promising materials toward each different application have been identified. Moreover, insights about the optimal structures were found to provide directions for future structure design and synthesis. For instance, one of our most recent works indicates that, for carbon dioxide capture, some zeolite structures that possess particular topologies resulted in constituting maximized density of ideal pockets for adsorbing CO₂ molecules, which can reduce the energy penalty imposed on a coal power plant by as much as 35% compared to the MEA technology.

A systematic and transferable methodology has also been developed to generate accurate force fields using high-level quantum chemical calculations. The method was first applied for flue gases inside Mg-MOF-74, an open-metal site MOF, and the obtained force fields can be used to well reproduce experimentally measured adsorption properties. In this original study, the Møller-Plesset second-order perturbation theory (MP2) with representative small framework fragments was used. To facilitate the automation of this methodology as well as resolve the intrinsic discrepancies between cluster and periodic calculations, a methodology based on the periodic density functional theory (DFT) calculations is therefore further introduced.

In this poster, advanced developments as well as insightful outcomes from the aforementioned screening studies and the methodology of generating accurate force fields will be highlighted. More importantly, the poster will demonstrate the potential of integrating all techniques, including those that are under development, to accelerate the search for promising materials toward various energy-related gas separation and storage applications.

Advisor: Prof. Berend Smit, Dept. of Chemical and Biomolecular Engineering and Chemistry, University of California – Berkeley