Preparation Of Mil-100(Fe) And HPW@MIL-100(Fe)Catalysts And Their Catalytic Properties

Metal-organic frameworks (MOFs), an important class of advanced functional materials, are currently eliciting much attention for their potential applications in the fields of gas storage, separation, drug delivery, and heterogeneous catalysis. The interest in MOFs arises from their high surface area, huge porosity, tunable pore size and functionality. Among known MOFs, several transition-metal MOFs have high hydrothermal and chemical stabilities. These include mesoporous iron(III) carboxylate [MIL-100(Fe)], which has a rigid zeotype crystal structure, consisting of2.5and2.9nm mesoporous cages accessible through window sizes of ca.0.55and0.86nm, respectively. Notably, the nature of the iron offers several advantages, compared to other metals, due to its low cost, non-toxicity, and environmentally-friendly character, which make MIL-100(Fe) an interesting candidate for many potential applications. In this thesis, new methods for the preparation of MIL-100(Fe) and HPW@MIL-100(Fe) catalysts were developed and their catalytic propertie were also systematically investigated. The main results are summarized as follows:Mesoporous metal-organic framework (MOF), MIL-100(Fe), has been successfully synthesized by a simple unappreciated low-temperature (<100℃) synthesis route via reaction of ferric nitrate and trimesic acid under HF-free conditions. The obtained MIL-100(Fe) was systematically characterized by XRD, N2adsorption, XPS, TGA, FT-IR, SEM, and in situ FT-IR spectroscopy of adsorbed pyridine, as well as used as heterogeneous catalysts for liquid-phase acetalization of various aldehydes with diols. The characterization results indicate that MIL-100(Fe) can be well prepared following the method described in this context. In comparison with other methods commonly used for the preparation of this MOF in the literature, the reported synthesis strategy has several merits such as mild and environmentally benign synthesis conditions, high MOF yield, as well as easy scale-up production. Additionally, the synthesized MIL-100(Fe) shows some excellent catalytic properties in the acetalization of various aldehydes with diols due to the Lewis acidity of its unsaturated metal sites, accompanied with abundant mesoporous cage in its framework, superior to the commercial resin and zeolite catalysts.12-Tungstophosphoric heteropolyacid (HPW) has been encapsulated in the mesoporous metal-organic framework (MOF), MIL-100(Fe), by one-pot synthesis route via reaction of ferric nitrate, trimesic acid and HPW under HF-free conditions. The resulting hybrid HPW@MIL-100(Fe) was systemically characterized by XRD, N2adsorption, FT-IR, acid-base titration,31P MAS NMR, XPS techniques, and elemental analysis, and then used as a heterogeneous catalyst for liquid-phase esterification of acetic acid with n-hexanol. The characterization results indicate that the HPW molecules were successfully encaged within the mesoporous cages of the MIL-100(Fe) matrix as noncoordinating guests with the integrated protonic acidity of HPW. The developed HPW@MIL-100(Fe) shows high catalytic activity and excellent reusability in the esterification without agglomeration, leaching and deactivation of HPW during its repeated use. The unique characteristics of MIL-100(Fe) and the well-dispersed level of HPW molecules in the mesoporous cages of the MIL-100(Fe) matrix may account for the high catalytic properties of HPW@MIL-100(Fe).