TY - JOUR

T1 - Seeding Layer Approach for the Synthesis of Co-ZIF-90 Thin Films of Optical Quality

AU - Keppler, Nils Christian

AU - Fricke, Johanna

AU - Schaate, Andreas

AU - Hannebauer, Adrian

AU - Hindricks, Karen Deli Josephine

AU - Zailskas, Saskia

AU - Behrens, Peter

N1 - Funding Information: This work was funded by the Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy within the Cluster of Excellence PhoenixD (EXC 2122, Project ID 390833453). Karen Hindricks thanks the Studienstiftung des Deutschen Volkes (German National Academic Foundation) for a scholarship. Adrian Hannebauer thanks the HSN (Hannover School for Nanotechnology) for a scholarship. We thank Younes Senft for building the UV/vis measurement cell.

PY - 2022/12/7

Y1 - 2022/12/7

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85143508384&partnerID=8YFLogxK

U2 - 10.1021/acs.cgd.2c00664

DO - 10.1021/acs.cgd.2c00664

M3 - Article

AN - SCOPUS:85143508384

VL - 22

SP - 7008

EP - 7020

JO - Crystal Growth and Design

JF - Crystal Growth and Design

SN - 1528-7483

IS - 12

ER -