Density Functional Theory Meta-GGA+U Study of Water Incorporation in the Metal Organic Framework Material Cu-BTC

摘要

Water absorption in the metal-organic framework (MOF) material Cu-BTC, up toa concentration of 3.5 H$_2$O per Cu ion, is studied via density functionaltheory at the meta-GGA+U level. The stable arrangements of water molecules showchains of hydrogen-bonded water molecules and a tendency to form closed cagesat high concentration. Water clusters are stabilized primarily by a combinationof water-water hydrogen bonding and Cu-water oxygen interactions. Stability isfurther enhanced by van der Waals interactions, electric field enhancement ofwater-water bonding, and hydrogen bonding of water to framework oxygens. Wehypothesize that the tendency to form such stable clusters explains theparticularly strong affinity of water to Cu-BTC and related MOFs with exposedmetal sites.