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

• Published in: Advanced functional materials 2014-08, Vol.24 (30), p.4804-4811
• Main Authors: Khaletskaya, Kira, Turner, Stuart, Tu, Min, Wannapaiboon, Suttipong, Schneemann, Andreas, Meyer, Robert, Ludwig, Alfred, Van Tendeloo, Gustaaf, Fischer, Roland A.
• Format: Article
• Language: English
• Subjects: Deposition; Formations; localized film growth; metal oxide films; Microbalances; nanolayers; Nanostructure; Nucleation; quartz crystal microbalance; Silicon substrates; Thin films; zeolitic imidazolate; Zinc oxide; ZnO
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201400559

Control of localized metal–organic framework (MOF) thin film 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 Zn2+ ions required for nucleation and localized growth of ZIF‐8 films ([Zn(mim)2]; Hmim = 2‐methylimidazolate). The obtained ZIF‐8 films 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 films derived from Al2O3 nanolayers. The self‐template route for the manufacturing of ZIF‐8 films on silicon (Si) and quartz crystal microbalance (QCM) substrates involves the pre‐deposition of ZnO films prepared by sputtering or atomic layer deposition methods and the subsequent conversion of the immobilized ZnO phase into crystalline and homogeneously dense ZIF‐8 films via microwave‐assisted synthesis.