Synthesis of thin film metal organic frameworks using aerosol assisted chemical vapour deposition

Abstract

Currently many methods used for the synthesis of MOF thin films are modifications of the solvothermal synthesis, and as such are not well suited for large scale synthesis. This project focuses on the use of aerosol assisted chemical vapour deposition (AACVD), a promising technique for industrial thin film synthesis. In this project it has been demonstrated that AACVD can offer a simple and scalable synthetic route to adherent and crystalline MOF thin films. The quality of the film was judged by its crystallinity, purity, adherence and coverage of the 15 x 5 cm substrate. 4 MOFs, ZIF-8, ZIF-67, Zn-CPO-27 and Co-CPO-27 have been successfully synthesised using AACVD on both glass and alumina. The twostep process involved the dissolution of the precursors into methanol, and the ultrasonication of the solution into an aerosol, which was carried into the reactor using argon. Through optimisation it was found that similar conditions were needed for the synthesis of all 4 films. The conditions were designed to limit MOF formation before entering the reactor, by modifying the precursor ratio and reactor temperature. Thin film thickness could be controlled by altering the quantity of precursors. Zinc oxide was deposited onto glass substrate prior to the MOF deposition to investigate the effect on the MOFs adherence. The film adherence was shown to improve with the roughness of the substrate surface. This was demonstrated as the adherence of the films was greatest on alumina, and worst on glass. The films adherence and coverage make these films promising for applications such as separation and catalysis. The films were also assessed for applications in gas separation by depositing on alumina membranes. The coverage was demonstrated to be good, with future applications looking promising.

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ORCID for Geoffrey Hyett: orcid.org/0000-0001-9302-9723

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