Functional materials in catalysis

  • Funktionale Materialien in der Katalyse

Krischel, Julian; RĂ¼ping, Magnus (Thesis advisor); Pich, Andrij (Thesis advisor)

Aachen (2020)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2020

Abstract

This work is an elaboration of the miscellaneous features of functional materials and the irimplementation in catalytic processes. At the outset, the properties are defined which characterize functionalized materials. In this context, the central scientific question was about how the structure-related properties can be modified to suit for possible applications. This was enabled through intense analytic investigation of the chemical and physical properties of the functional materials by various analytical methods. Two materials which are different in nature were tested for their functionality and applicability to serve as micro structured materials in multiple catalytic processes. At first, based on rigid building blocks, a polymer was crafted which unpredictably assembled into polymer nanotubes. Transmission electron microscopy gave decisive insights into the assembly process and furthermore allowed the direct visualization of the interior 3D structure via tomography. After the thoroughly investigation of various physical as well as chemical properties the polymer nanotubes turned out to be suitable as supporting material for metal nanoparticles as well as a photo catalysts. Contrary to the rigid polymer nanotubes the development of responsive microgels, which adapt to their surrounding environment, could pave the way towards the utilization of soft matters for catalysis. Inspired by the idea of a recyclable microgel reactor a poly(N-vinylcaprolactam)based microgel with a charged shell was crafted as a carrier system for gold and palladiumnanoparticles. Here, the first direct visualization of a microgel 3D structure by cryo-TEMtomography enabled the intense analysis under native and none-native condition. In addition to that, the micro reactor showed excellent activity in catalyzing the Suzuki-Miyaura coupling in water as sole solvent. Besides its responsive and adaptive behaviour, the flexible polymeric network turned out to be ideal for the growth and stabilization of different nanoparticles of small sizes. Accordingly, asecond microgel with the ability to swell at higher temperatures was crafted and loaded with ruthenium nanoparticles as versatile catalytically active sites. The ruthenium based microgel reactor showed promising activity in the dehydrogenation of hydrogen carriers like hydroushydrazine and formic acid. The hydrogen released in this process could directly be used for the catalytic transformation of various nitroarenes.

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