Epitaxial Growth of γ‑Cyclodextrin-Containing Metal–Organic Frameworks Based on a Host–Guest Strategy

• Published in: Journal of the American Chemical Society 2018-09, Vol.140 (36), p.11402-11407
• Main Authors: Shen, Dengke, Wang, Gang, Liu, Zhichang, Li, Peng, Cai, Kang, Cheng, Chuyang, Shi, Yi, Han, Ji-Min, Kung, Chung-Wei, Gong, Xirui, Guo, Qing-Hui, Chen, Hongliang, Sue, Andrew C.-H, Botros, Youssry Y, Facchetti, Antonio, Farha, Omar K, Marks, Tobin J, Stoddart, J. Fraser
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b06609

A class of metal–organic frameworks (MOFs)namely CD-MOFsobtained from natural products has been grown in an epitaxial fashion as films on the surfaces of glass substrates, which are modified with self-assembled monolayers (SAMs) of γ-cyclodextrin (γ-CD) molecules. The SAMs are created by host–guest complexation of γ-CD molecules with surface-functionalized pyrene units. The CD-MOF films have continuous polycrystalline morphology with a structurally out-of-plane (c-axial) orientation, covering an area of several square millimeters, with a thickness of ∼2 μm. Furthermore, this versatile host–guest strategy has been applied successfully in the growth of CD-MOFs as the shell on the curved surface of microparticles as well as in the integration of CD-MOF films into electrochemical devices for sensing carbon dioxide. In striking contrast to the control devices prepared from CD-MOF crystalline powders, these CD-MOF film-based devices display an enhancement in proton conductance of up to 300-fold. In addition, the CD-MOF film-based device exhibits more rapid and highly reversible CO2-sensing cycles under ambient conditions, with a 50-fold decrease in conductivity upon exposure to CO2 for 3 s which is recovered within 10 s upon re-exposure to air.