A Strategy for Trapping Molecular Guests in MOF-5 Utilizing Surface-Capping Groups

We have developed a simple strategy allowing molecular guests to be trapped within MOF-5 using carboxylic acids bearing sterically demanding substituents as capping reagents. We demonstrate that introducing triphenylacetic acid or diphenylacetic acid onto the surface of crystals of MOF-5 loaded with crystal violet (CV) prevents CV from escaping by blocking the openings of pores. In this study, MOF-5 was capped with four carboxylic acids and two 3 degrees amines, and diffusion of CV out of capped MOFs was monitored using UV-vis spectroscopy to assess how variation in the steric demand of substituents affected retention of CV.