Katalytische omzetting van koolstofdioxide naar Organic carbonaten

Catalytic Conversion of Carbon Dioxide into Organic Carbonates The utilization of carbon dioxide as a source of carbon in synthetic chemistry appears very attractive since CO2 is widely available, inexpensive, nontoxic and continuously produced by human activities. Atom-efficient fixation of CO2 with epoxides to valuable products with growing applications as cyclic carbonates or polycarbonates has received much attention. This process requires a catalyticnbsp;containing Lewis acid sites for the electrophilic activation of epoxide and/or carbon dioxide and Lewis base sites acting as nucleophiles. In this thesis, newnbsp;catalysts were investigated to promote the coupling reaction of CO2 with epoxides. The idea is to develop inexpensive,nbsp;stable and easily prepared catalysts with high activity to promote this reaction. Highly stable and easily synthesized zinc(II) salphen, iron(III) pyridylamino-bis(phenolate),nbsp;iron(III) amino-triphenolate complexes were studied as homogeneous catalysts in the selective synthesis of either cyclic carbonates or polycarbonates.nbsp;Tuning the electronic and stericnbsp;of ligands and the influence on the catalyticnbsp;were investigated. The parameters affecting the activity and the selectivity of the reaction such as the nature of the epoxide, the type and loading of additional co-catalyst, the reaction temperature, the CO2 pressure, the solvent, the reaction time, the presence of impurities as well as thenbsp;properties (regio- and stereochemistry and glass transition temperature) of the obtained polycarbonates were systematically investigated. Controllable activity and selectivity towards the target product was obtained by fine tuning those parameters. With zinc(II) salphen, remarkable activity andnbsp;selectivity for the synthesisnbsp;cyclic carbonate from a variety of epoxides was achieved. Changing the ligand scaffold from planar to trigonal bipyramidal and thenbsp;center from Zn(II) to Fe(III)nbsp;in highly active catalyst iron(III)nbsp;with a switchable selectivity towards eithernbsp;or cyclic carbonate achieved by changing thenbsp;type and the catalyst/co-catalyst ratio. Tuning the structure by incorporating an axialnbsp;ligand gave iron(III) pyridylamino-bis(phenolate) that showed catalytic activity alone; its performancenbsp;be improved by adding a nucleophilic co-catalyst. With this catalyst, an unexplored epoxide (1,2-epoxy-4-vinylcyclohexane) was successfully polymerized with nearlynbsp;selectivity towards polycarbonate.nbsp;of the obtained polycarbonate was explored as a strategy to improve thermalnbsp;chemical resistance of the polymer. Since heterogeneous catalystsnbsp;reusable, they are more suitable for industrial application compared to homogeneous catalysts. Metal organic frameworksnbsp;were studied as heterogeneous catalysts in the selective synthesis of cyclic carbonates from CO2 and epoxides. MOFs with coordinatively unsaturated sites possessing Lewis aciditynbsp;large pore size, innbsp;to have no diffusion problem,nbsp;chosen. Strategies towards improving structural stability of MOFs in this cycloaddition reaction were investigated. The parameters determining the catalytic activity of MOFsnbsp;as the structure, the pore size, Lewis acidity of the metal centers, the organic linkers, nucleophilic substituent on the organic linkers were systematically investigated. High-throughput experimentation allowed fast and reliable comparison of various catalysts and of different reaction conditions,nbsp;improvingnbsp;efficiency in screening and optimizing the above-mentioned catalytic systems.status: publishe