The ability to design and tailor the growth of surface-anchored metal organic frameworks (surMOFs) permits controlled assembly processes to enhance a material’s viability for applications such as catalysis, sensing, and absorption. SurMOFs are a class of nano-porous crystalline materials assembled from metal-based nodes and bridging organic ligands. To produce surface-anchored MOF films with controlled thickness and surface coverage, liquid-phase epitaxy (LPE) is commonly employed to deposit films by introducing the metal ion source and the organic linker in an alternating, sequential solution-phase deposition process. This research investigates the bottom-up assembly of SurMOFs and examines various growth parameters to optimize assembly and to provide further insight into the fundamental forces that drive SurMOF growth. To fabricate SurMOF thin films, we employed LPE to deposit MOF-14 on gold substrates functionalized with self-assembled monolayers (SAMs). SurMOF thin films were subsequently characterized via ellipsometry, contact angle goniometry, and atomic force microscopy. We have successfully demonstrated the ability to control SurMOF thickness and morphology by altering the identity and conditions of the underlying substrate. More specifically, we employed varying concentrations of carboxylic acid and methyl terminated alkanethiol self-assembled monolayers, investigated various deposition times, and utilized post-deposition processing, which included exposure to dilute acidic solutions and metal salt solutions. Methyl-terminated alkanethiol SAMs of varying lengths were also studied to investigate if they effectively inhibit surMOF formation. Because these parameters influenced SurMOF assembly in a well-controlled fashion, this research offers new insight into the preparation of high-quality surMOFs for targeted applications. More specifically, by exploring surMOF growth mechanisms, this research paves the way for the development of new types of surMOFs that maintain fewer and well-regulated defects, grain boundaries, and in-plane orientation.

Investigating how the anchoring monolayer can tailor film morphology of surface-bound MOF-14

ACS Spring 2022

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