Surface and Stability Characterization of a Nanoporous ZIF-8 Thin Film

Abstract

Zeolitic imidazolate frameworks (ZIFs) have been widely investigated for numerous applications including energy storage, heterogeneous catalysis, and greenhouse gas adsorption. Much of the early work has focused on the bulk properties of microcrystalline ZIFs. Herein, we focus on identifying the nature of the surface of ZIF-8 by studying a supported ZIF-8 nanoparticle film using surface characterization techniques. We have experimentally identified the presence of a zinc-rich surface terminated by carbonates and water/hydroxyl groups (in addition to the expected methylimidazole terminations) using X-ray photoelectron spectroscopy (XPS). The thermal stability of ZIF-8 thin films was also investigated using scanning electron microscopy (SEM) and temperature-programmed reaction spectroscopy (TPRS). We determined the onset of decomposition of ZIF-8 thin films to be approximately 630 K using TPRS in an ultrahigh vacuum (UHV) environment. This work presents the first characterization steps needed to study the evolution of ZIF surfaces in situ using surface characterization techniques. Such techniques are capable of determining reaction products and tracking intermediates and surface evolution in gas adsorption/reaction studies of thin films.

One-step synthesis of nanostructured mesoporous ZIF-8/silica composites

“…In the C1s and N1s region ( Fig. 2a and b), two signals around 399.2 eV for N1s and 284.8 eV for C1s are found, respectively, which are consistent with N and C of the ligand [30,31]. In the zinc region (Fig.…”

Secondary growth of ZIF-8 films onto copper-based foils. Insight into surface interactions

“…When analyzing the C1s and N1s regions (Fig. S5), symmetrical signals around 398.7 eV for N1s and 284.8 eV for C1s were found which are consistent with N and C of the ligand [54]. Moreover, signals of Cu 2p 3/2 centered at 932.2 eV which are typical of Cu 1þ (Fig.…”

In Situ Measurement of CO2 and H2O Adsorption by ZIF-8 Films

“…16 In identifying and studying non-native exterior surface groups, we employ ZIF-8 nanoparticle films prepared in a manner previously reported by Demessence et al, who demonstrated that film thickness could be controlled using a simple dip-coating process. 17 Reported uses for ZIF films include chemical vapor sensors 18 and membranes for petrochemical separation.…”

“…19,20 In our earlier studies of such films we demonstrated that carbonates and water/hydroxides terminate the outermost surfaces in addition to the expected methylimidazolate groups. 16 Herein, we compare the adsorption of CO 2 to that of water under low-pressure (10 −9 −10 −6 Torr), low-temperature (exposure temperature ∼90 K) conditions using ZIF-8 nanoparticle films in a fundamental study. We show that a distinction can be made between molecules which bind to outer surfaces of the film and those which penetrate into the pore structure using a combination of in situ X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD).…”