Design of new materials for methane storage.

One of the strategic goals of the modern automobile manufacturing industry is to replace gasoline and diesel with alternative fuels such as natural gas. In this report, we elucidate the desired characteristics of an optimal adsorbent for gas storage. The U.S. Department of Energy has outlined several requirements that adsorbents must fulfill for natural gas to become economically viable, with a key criterion being the amount adsorbed at 35 bar. We explore the adsorption characteristics of novel metal-organic materials (IRMOFs and molecular squares) and contrast them with the characteristics of two zeolites, MCM-41, and different carbon nanotubes. Using molecular simulations, we uncover the complex interplay of the factors influencing methane adsorption, especially the surface area, the capacity or free volume, the strength of the energetic interaction, and the pore size distribution. We also explain the extraordinary adsorption properties of IRMOF materials and propose new, not yet synthesized IRMOF structures with adsorption characteristics that are predicted to exceed the best experimental results to date by up to 36%.