Low-Temperature Adsorption and Diffusion of Methanol in ZIF-8 Nanoparticle Films

The adsorption of methanol by a zeolitic imidazolate framework-8 (ZIF-8) nanoparticle thin film was studied in situ using temperature-programmed desorption and X-ray photoelectron spectroscopy under low-temperature, low-pressure conditions. Partial pore penetration was observed at 90 K, but upon increasing the exposure temperature of the film to 130 K pore penetration was significantly enhanced. Although many studies exist involving bulk powders, this is the first work to our knowledge that demonstrates the ability to control and monitor the entry of a molecule into a metal organic framework (MOF) film in situ using temperature. In this case, nanoparticle films of ZIF-8 were prepared and studied in ultrahigh vacuum. The ability to control and monitor surface adsorption versus pore adsorption in situ is key to future fundamental study of MOFs, for example, in the identification of active sites in reaction mechanisms.