Self-Assembled Mesoporous Zeolitic Imidazolate Framework-8 (ZIF-8) Nanocrystals Bearing Thiol Groups for Separations Technologies

Abstract

Colloidal suspensions of Zn-based ZIF-8 metal–organic framework (MOF) particles were synthesized (both micrometer μ-ZIF-8- and nanometer n-ZIF-8-sized, respectively). Postsynthetic modification was carried using 2-amino-ethanethiol (cysteamine or Cys), a thiol-bearing monodentate ligand, and particles obtained were employed for the assembly of films on gold-coated electrode surfaces. The results obtained show that, aside from conferring chemical affinity toward Au, when suitable molar ratios are employed, cysteamine modification causes partial coordinative chemical etching of inherently microporous ZIF-8 units, thus giving rise to additional mesoporosity. Cysteamine concentration and exposure time were found to act as control parameters ultimately determining the transport properties of porous films obtained, which can then feature, e.g., size-exclusion effects. The colloidal modification strategies like the one hereby described can be employed for the preparation of robust nano-organized MOF thin films with hierarchical porosity, which bear great potential for its application in separation technologies.

Nanoarchitectonics of metal organic frameworks and PEDOT layer-by-layer electrodes for boosting oxygen reduction reaction

“…Furthermore, a SEM image of a 3x-ZIF-8-(PEI/PEDOT) 4 substrate is shown in Figure 2A, where a top view of a film showing the nanocrystals of the deposited MOF can be seen, as previously reported. 75,76 When compared with the SEM picture of a (PEI/PEDOT) 4 substrate (Figure S1), the differences ascribed to the deposited MOF layer are clearly evidenced.…”

Post-synthetic modification and chemical modulation of the ZIF-8 MOF using 3-mercaptopropionic acid (MPA): a multi-technique study on thermodynamic and kinetic aspects

“…S2 †). Based on previous reports for similar systems, 26 we hypothesized that the above described PSM approach should lead to the appearance of additional mesoporosity on inherently microporous ZIF-8 units, arising from coordinative etching triggered by affinity between Zn 2+ and carboxylate moieties. The extent of such modifications can be controlled in principle via manipulation of reaction conditions such as temperature, exposure period or modifying agent concentrations.…”

“…In addition, we have recently found similar results with thiol-functionalized ZIF-8 nanocrystals using cysteamine as a functionalizing agent. 26…”

“…Therefore, we consider that this is a promising strategy for the design of porous (both micro and meso) colloidal building blocks with tailored affinity towards metallic surfaces, with multiple possibilities in the design of functional nanoarchitectures. 26,54…”

“…In this regard, it was recently shown that the constructional mesoporosity of ZIF-8 films (directly related to the possibility of selective permeation in aqueous environments) can be tuned by careful design of porous nanounits. 26,27 Moreover, it was shown also that such control can be exploited for the design of composite films in which insulating ZIF-8 nanounits and conducting polymers (CPs) are synergically combined. These films were demonstrated to be cost-effective prospective electroactive catalysts with increased efficiency towards the energy relevant oxygen reduction reaction (ORR).…”