The Preparation Of Nanocatalysts Based On Cucurbit "n" Uril And Their Catalytic Properties

The goal of this dissertation is to study the fabrication of nanocatalysts with high catalytic activities by using cucurbit[n]uril (CB[n], n=6) as stabilizer/support. CB[n] is a class of excellent stabilizer and support for nanomaterials, which are verified by experiments involving the design, preparation and performance investigation of nanocatalysts based on such material. The design of the projects is based on its insolubility in common solvents, high thermal stability, chemical stability, and symmetrical structure of CB[n]. The details are summarized as follows:1. Four types of palladium nanoparticles, CB[n]-Pd NPs (n=5, 6, 7, 8), were prepared using four different kinds of CB[n]. Pd nanoparticles can be stabilized by the electrostatic interactions between the surface atoms of the nanoparticles and the carbonyl-laced portals of CB[n]. CB[n] also acts as the support for the nanocatalysts due to its insolubility in common solvents. The morphologies of different CB[n]-Pd NPs (n=5-8) studied. The investigation concerning the differences of appearance, dispersity, and particle diameter were also carried out. Pd NPs with controlled shapes and size were prepared by changing the molar ratio of CB[6] to metal precursor. Additionally, many reduction methods were utilized to attain CB[n]-Pd NPs with different shapes and rich twinned planes.2. The catalytic performances of CB[n]-Pd NPs (n=6, 7) for C-C coupling reactions were investigated. With ethanol/water as solvent, Suzuki reactions proceeded smoothly under mild conditions. The conditions for the Heck reactions were also tested. Up to 99% yield was obtained employing aryl halides and chain olefins as the coupling partners in the presence of CB[6]-Pd NPs.3. Four different CB[6]-Pt NPs were fabricated using different reduction methods, and their morphologies were studied based on TEM and XRD. In addition, four Pt NPs with novel morphologies were synthesized via simple procedure: 1) Pt nanoflowers with 3D complicated surface structures and high surface area; 2) Pt nanoparticles with rich twinned planes and stacking faults; 3) Pt nanoparticles with branch; 4) Pt nanoparticles with good dispersion and with particles size less than 2 nm. The growth mechanisms of CB[6]-Pt NPs with different morphologies were proposed, which further demonstrated the unique merits of CB[n] in the fabrication of nanoparticles.. 4. The electrochemical performance of CB[6]-Pt NPs were studied. Such nanoparticles showed low onset potential, high current density, and high If / Ib value for methanol oxidation, which indicates that the CB[6]-Pt NPs exhibit excellent catalytic properties and good anti-poisoning abilities for methanol MORs. Then, the catalytic performances of CB[6]-Pd NPs for electrooxidation of formic acid were studied, which shows good electrocatalytic activities. These results further certified that CB[n]-M NPs (M= Pd, Pt) have excellent catalytic performances because the active sites on surface of these nanoparticles are fully exposed.5. An organic-inorganic hybrid compound which is composed of CB[6] and polyoxometalate (POMs) was prepared by using in-situ method. Supramolecules were formed via abundant hydrogen bonding interaction of organic and inorganic building blocks. Under visible light irradiation, the organic building block could act as a sensitizer and transfer electrons to the LUMO of POMs via the hydrogen bonding network, thereby, inducing the formation of radicals that are responsible for the degradation of dye molecules. As photocatalysts, CB[6]-POMs is superior to the POMs, owing to its utilization of visible light and insolubility in common solvents. Thess studies also show the great potential of CB[6] in environmental protection.