Zeolitic imidazolate frameworks (ZIFs) have strong potential for numerous applications in energy-related gas storage, catalysis, and sensor development. Much of the work to this point has focused on the synthesis and investigation of the bulk properties of microcrystalline ZIFs. In this study, we focus on nanoporous ZIF-8 thin films supported on a Au substrate as many applications depend on the preparation of films. More importantly, the study of such films can provide fundamental insight into adsorption and reaction mechanisms.  We used X-ray photoelectron spectroscopy (XPS) to determine the identity of the surface-terminating groups, the first groups encountered by any entering gases. In parallel, we investigated the adsorption of energy-related gases, including CO2, H2O, and methanol by ZIF-8 films using temperature programmed reaction spectroscopy (TPRS).    By combining these techniques with quartz crystal microbalance (QCM) measurements of film mass, we were able to determine gas uptake of the films and compare these uptakes to bulk measurements. Under low-temperature, low-pressure conditions, we observed uptakes of CO2 very similar to that of the bulk microcrystalline ZIF-8, while uptake of water is limited, likely due to hydrogen bonding interactions with external terminating surface groups. This work reveals a method which allows one to distinguish between species which occupy the pores of the film from those which reside at the surface, and demonstrates more generally the ability to monitor the interactions of gases with supported nanoporous materials in ultra-high vacuum, opening the door to understanding mechanisms of adsorption and reaction of gases of interest.

Surface reactivity of nanoporous ZIF-8 thin film toward energy-related gases

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.