Study on a new method of film formation of MOFs: preparation of high crystallinity film by VAC method

Metal organic frameworks, or MOFs for short, are nanoporous crystalline materials formed by self-assembly of organic ligands and metal ions or clusters via coordination bonds Because of the characteristics of MOFs frame structure, related materials usually have high specific surface area, regular, orderly and adjustable pore size and shape, and easy to functionalize Therefore, MOFs materials have a strong attraction in assembling functional films Compared with the traditional zeolite materials, the structure of MOFs has more diverse pore size and shape, in which the flexible pore can adjust the pore size reversibly to adapt to the adsorbate, making it more widely used In recent years, the metal organic framework based films have achieved great success in small molecule separation, sensors, membrane catalytic reactors and other fields Recently, Professor Dana D Medina and Stefan Wuttke from the University of Munich, Germany, adopted the dry gel conversion (DGC) and steam assisted conversion, A new method, vapor assisted conversion (VAC), has been developed for the preparation of metal organic frameworks by sac, and zirconium based metal organic frameworks have been prepared on various substrate surfaces by this method This achievement was published in the Journal of the American Chemical Society (DOI: 10.1021 / JACS 7b08174) under the title of "on surface synthesis of highly oriented thinmetal – organic framework films through vapor assisted conversion" (source: j.a.c.s ASAP, 10.1021/jacs.7b08174) as shown in Figure 1, the equipment required for the preparation of organic metal framework by VAC method is relatively simple: a glass container is used as the reactor, and a glass platform is used as the support platform At the beginning of preparation of MOFs, the mixture of DMF and acetic acid is added to the container as the steam source, then the required substrate is placed on the support platform, then a certain amount of precursor solution (DMF solution with a certain proportion of zirconium, dicarboxylic acid and acetic acid) is added to the substrate, finally the container is sealed and kept at 100 ° C for 3 h After the reaction is complete, the corresponding MOFs membrane can be obtained only after the substrate is taken out and dried By this method, a series of MOFs thin films were prepared on the gold and silicon surfaces, and characterized by XRD, SEM and AFM In addition, the effects of reaction conditions on the formation of MOFs film, such as the composition, concentration and addition of precursor solution, reaction temperature and reaction time, were analyzed in detail It was found that acetic acid in precursor solution can regulate the crystallization process of MOFs and further affect the crystallization process of MOFs film, while the reaction time of 3 hours and reaction temperature of 100 ° C are the necessary conditions for the formation of MOF film In addition, the adsorption experiment of ethanol also proved that the MOFs prepared by this method also has porous structure and can be used to prepare porous film materials Fig 2 XRD patterns of MOFs films prepared by VAC method (source: j.a.c.s ASAP, 10.1021 / JACS 7b08174) Full text author: Erika virmani, Julian M Rotter, Andre m ä hringer, Tobias von zons, ADELHEID godd, Thomas bein, Stefan wutke, and Dana D Medina