Seeding Layer Approach for the Synthesis of Co-ZIF-90 Thin Films of Optical Quality

authored by

Nils Christian Keppler, Johanna Fricke, Andreas Schaate, Adrian Hannebauer, Karen Deli Josephine Hindricks, Saskia Zailskas, Peter Behrens

Abstract

The growth of zeolitic imidazolate framework (ZIF) thin films is an interesting topic, since ZIFs have a high thermal and chemical stability compared to many other MOFs. A variety of functionalities can be introduced via the imidazole linker molecule. Here, we report on a new approach for the preparation of thin films of a novel ZIF material: Co-ZIF-90. The preparation of thin films is possible on silicon or glass when ZIF-8 seeding layers are deposited first. The resulting constructions are effectively MOF-on-MOF layer systems. The synthesis procedure has been optimized with regard to obtaining high-quality thin films of Co-ZIF-90 on ZIF-8 for optical applications. Notably, the preparation of Co-ZIF-90 thin films is possible only by using a mixture of two different cobalt precursor salts (acetate and nitrate). The thin films are characterized in detail. With regard to the use as an optical material, UV-vis absorption spectra of the MOF-on-MOF constructs were measured and the refractive index of Co-ZIF-90 was determined using ellipsometry. Furthermore, the refractive index of the Co-ZIF-90 film can be modulated reversibly by the adsorption and desorption of water via the gas phase. The kinetics of this fast process are on the time scale of 1 s. In addition to the preparation of thin films, we obtained Co-ZIF-90 as a powder sample and basically characterized the powder. The approach to use an easy-to-crystallize ZIF-8 film as a seeding layer for the growth of films of other ZIFs may be extended as a general concept for the deposition of crystalline ZIF layers in such cases, where a direct deposition is difficult or not possible.

Organisation(s)

PhoenixD: Photonics, Optics, and Engineering - Innovation Across Disciplines
Institute of Inorganic Chemistry
Inorganic Solid State and Materials Chemistry group
Hannover School for Nanotechnology

Type

Article

Journal

Crystal Growth and Design

Volume

22

Pages

7008-7020

No. of pages

13

ISSN

1528-7483

Publication date

07.12.2022

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Chemistry(all), Materials Science(all), Condensed Matter Physics

Electronic version(s)

https://doi.org/10.1021/acs.cgd.2c00664 (Access: Open)