(693a) Computational Screening of Functional Groups for Ammonia Capture in Metal-Organic Frameworks

Metal-organic frameworks (MOFs), an emerging class of porous crystalline materials, are three-dimensional network materials consisting of metal clusters regularly coordinated by organic ligands. They are of great interest for gas separation, gas storage, and catalysis applications due to their high surface area, tunability, versatility, and functionality. These features also suggest that MOFs could be useful materials for capture of toxic gases, such as ammonia, but to date, only a few studies have reported on the adsorption of ammonia in MOFs.  In this study, we have used computational methods to screen and assess functional groups that could be incorporated into MOF ligands to preferentially adsorb ammonia under humid conditions. Using quantum chemical calculations, we examined the binding energies of ammonia and water with twenty-two different functional groups. Among the functional groups, a few carboxylate salts are predicted to be the top candidates for ammonia capture under both dry and humid conditions.  The calculations also provide detailed information on the modes of binding.  For example, the possibility of ammonia protonation on acidic functional groups was investigated.