Solvent-Free Powder Synthesis and MOF-CVD Thin Films of the Large-Pore Metal–Organic Framework MAF‑6

• Published in: Chemistry of materials 2020-03, Vol.32 (5), p.1784-1793
• Main Authors: Stassin, Timothée, Stassen, Ivo, Marreiros, João, Cruz, Alexander John, Verbeke, Rhea, Tu, Min, Reinsch, Helge, Dickmann, Marcel, Egger, Werner, Vankelecom, Ivo F. J, De Vos, Dirk E, Ameloot, Rob
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/acs.chemmater.9b03807

A simple solvent- and catalyst-free method is presented for the synthesis of the large-pore metal–organic framework (MOF) MAF-6 (RHO-Zn­(eIm)2) based on the reaction of ZnO with 2-ethylimidazole vapor at temperatures ≤100 °C. By translating this method to a chemical vapor deposition (CVD) protocol, crystalline films of a large-pore material could be deposited for the first time entirely from the vapor phase. A combination of positron annihilation lifetime spectroscopy (PALS) and Kr physisorption measurements confirmed the porosity of these MOF-CVD films and the size of the MAF-6 supercages (diameter ∼2 nm), in close agreement with powder data and calculations. MAF-6 powders and films were further characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), pair distribution function (PDF), and extended X-ray absorption fine structure (EXAFS). The exceptional uptake capacity of MAF-6 in comparison to ZIF-8 is demonstrated by vapor-phase loading of a molecule larger than the ZIF-8 windows.