Abstract

The large surface area ofmetal-organic frameworks (MOFs) sparks great interest for their use in storage applications. While the bulk of MOF applications focuses on incorporation of gases, we demonstrate that these highly porous frameworks are also well-suited for metal ion storage. For well-defined, highly oriented surface-anchored MOF thinfilms grown on modified gold surfaces using liquid-phase epitaxy (LPE), also referred to as SURMOFs, we determined theloadingof two different types of MOF materials with a total of seven types of metal ions (Zn2+, Ag+, Pd2+, Fe3+, Cd2+, Ni2+ and Co2+). Measurements using a quartz crystal microbalance (QCM) allowed determination ofloading capacities as well as diffusion constants in a quantitative fashion. The adsorption capacities were observed to be highly ion specific; the largest uptake was for Fe3+ and Pd2+ ions with six and four metal ions per MOF pore, respectively. By comparing results for SURMOFs fabricated from different types oflinkers, we demonstrate that S-containing functionalities in particular drastically improve the storage capacityof MOFs for metal ions.