Surface etching of HKUST-1 promoted via supramolecular interactions for chromatography
The addition of guanidinium-based surfactants to the synthesis of HKUST-1 reveals a novel surface patterning effect where meso- and macroscopic features appear on the MOF crystals. The size of the features increases with increasing alkyl chain length of the guanidinium amphiphiles, and their formation is strongly dependent on the presence of water which appears to more favourably etch the crystal surfaces when the surfactants are employed. The patterned crystals display intermediate type I/IV isotherms and the presence of the surface features have been evaluated for the chromatographic separation of styrene and ethylbenzene. Some degree of control over the interactions between the framework building blocks and the amphiphiles is afforded, and by simply changing the order of addition of the reactants the guanidinium surfactants promote the formation of HKUST-1 nanoparticles.