Self‐Directed Localization of ZIF‐8 Thin Film Formation by Conversion of ZnO Nanolayers

Abstract

Control of localized metal-organic framework (MOF) thin fi lm formation is a challenge. Zeolitic imidazolate frameworks (ZIFs) are an important sub-class of MOFs based on transition metals and imidazolate linkers. Continuous coatings of intergrown ZIF crystals require high rates of heterogeneous nucleation. In this work, substrates coated with zinc oxide layers are used, obtained by atomic layer deposition (ALD) or by magnetron sputtering, to provide the Zn 2+ ions required for nucleation and localized growth of ZIF-8 fi lms ([Zn(mim) 2 ]; Hmim = 2-methylimidazolate). The obtained ZIF-8 fi lms reveal the expected microporosity, as deduced from methanol adsorption studies using an environmentally controlled quartz crystal microbalance (QCM) and comparison with bulk ZIF-8 reference data. The concept is transferable to other MOFs, and is applied to the formation of [Al(OH)(1,4-ndc)] n (ndc = naphtalenedicarboxylate) thin fi lms derived from Al 2 O 3 nanolayers.

An innovative approach for the preparation of confined ZIF-8 membranes by conversion of ZnO ALD layers

“…Although high rate of heterogeneous nucleation can be expected from the ALD nanolayers [27], the zinc source is not easily dissociated to Zn 2 þ in the considered reaction conditions and relatively low ZIF-8 formation rates are expected. This could be an additional attractive parameter for better controlling the membrane formation and uniformity.…”

ZIF-8 membranes with improved reproducibility fabricated from sputter-coated ZnO/alumina supports

“…Magnetron sputtering technique was considered as a powerful methodology for highly controllable deposition of nano-scale metal oxides on various substrates (Ellmer, 2001;Khaletskaya et al, 2014). Herein, we report the successful partial self-conversion of sputtered-coated ultrathin ZnO layer to continuous ZIF-8 membranes on porous α-alumina support.…”

“…Partial self-conversion of inorganic support to metal-organic frameworks (MOFs) membrane can effectively promote the heterogeneous nucleation and enhance the binding strength between MOF grain and support, improving the reproducibility of as-synthesized membranes (Dong et al, 2012;Guo et al, 2009;Hu et al, 2011;Khaletskaya et al, 2014;Liu et al, 2014b;Marti et al, 2013;Zhang et al, 2013;Zhang et al, 2014). For example, Jin et al (Hu et al, 2011) prepared continuous MIL-53(Al) membranes on α-alumina supports, in which the α-alumina support acted as the inorganic source reacting with the organic ligand to grow a seeding layer.…”

Fabrication of functional hollow microspheres constructed from MOF shells: Promising drug delivery systems with high loading capacity and targeted transport

“…Since the discovery of ZIFs, they have emerged as ideal candidates and have been studied extensively for biomedical applications131415. Among ZIF materials, ZIF-8 is the most frequently studied because of its exceptional chemical and thermal stability1617. ZIF-8, which is composed of Zn and 2-methylimidazole, has sufficiently large pore apertures for passing drug molecules.…”