Free energy landscape for adsorption of gases on metal-organic frameworks (MOFs) and other complex nanostructures

Abstract

Metal organic frameworks (MOFs), carbon nanostructured materials and other porous materials play key scientific and technological roles in strategic areas such as renewable and sustainable energy production, green chemistry, and related fields. MOFs and other complex nanostructured materials are pivotal matrices for carbon capture and sequestration, post-combustion gas separation processes, hydrogen storage, and catalysis (e.g., synthesis of heavier organic compounds starting from CH4 and/or CO2). The adsorption of light gases by high-surface-area materials is a fundamental phenomenon underlying the above-mentioned technologically promising features of these materials. In this project, we propose to investigate the free energy density landscape for the adsorption of light gases (e.g., CO2, CH4, H2, O2) on complex nanostructured porous materials (MOFs, carbon nanostructures and others) using advanced computational methods suitable to large-scale molecular problems. We propose to use a molecular theory of solvation known as 3-dimensional reference interaction site model (3D-RISM), combined with other molecular simulation techniques, to create detailed maps of the local binding affinity (adsorption free energy landscape) for different gases of interest around the atomic sites of the nanostructured material (host) under different thermodynamic conditions of temperature and pressure. Previous studies in this area have been carried out in our group, in collaboration with Tom Woo's group at Ottawa University (Canada), using conventional modeling techniques such as Grand Canonical Monte Carlo simulations with carbon nanostructures as hosts (FAPESP/CEPID 2013/08293-7 and FAPESP/CALDO 2013/20381-10). Here, we intend to greatly extend the range of porous materials to include MOFs, to investigate different types of gases (especially greenhouse gases) and, most importantly, to adopt an entirely new approach to the gas-host adsorption problem based on the 3D-RISM method.