GRADUATE SCHOOL OF SCIENCES & ENGINEERING
CHEMICAL AND BIOLOGICAL ENGINEERING
MS THESIS DEFENSE BY VAHID NOZARI
Title: Towards Rational Design of Ionic Liquid/Metal-Organic Framework Composites: Effects of interionic interactions in Ionic Liquids
Speaker: Vahid Nozari
Time: June 13, 2018, 11.00
Place: ENG B05
Rumeli Feneri Yolu
Thesis Committee Members:
Assoc. Prof. Alper Uzun (Advisor, Koç University)
Assoc. Prof. Seda Keskin-Avcı (Advisor, Koç University)
Prof. Can Erkey (Koç University)
Assist. Prof. Sarp Kaya (Koç University)
Prof. Ramazan Yıldırım (Boğaziçi University)
Metal-organic frameworks (MOFs) are nanoporous materials, consist of organic linkers and inorganic metal constituents. Because of their structural functionalities, they have been investigated for a variety of applications such as gas storage and separation, catalysis, and sensing. To introduce further functionality into MOF structure and modify the framework for a target application, ionic liquids (ILs) have been used as a simple post-synthetic modification agent. Since the ILs are composed of ion pairs, by changing either the structures of cations or anions, one can synthesize an almost infinite number of varieties with different physicochemical properties. The challenging part in the modification of MOFs with IL incorporation is the proper choice of an IL. In this thesis study, the effects of interionic interaction energy in ILs on gas storage and separation performance and the thermal stability limits of the composites were investigated by introducing two different systematic changes on the IL structure: changing the anion structure and methylation of the proton on the C2 position of the imidazolium ring.
In the first part, three different preparation techniques were examined to synthesize an IL/MOF composite. Influence of different preparation routes on the adsorption performance of the composite as well as its structural properties were investigated. Wet impregnation technique was selected as a proper way of preparing IL/MOF composites compared to ship-in-a-bottle and incipient wetness methods. Since this technique is not time and energy consuming, it can be employed to synthesize any combination of IL/MOF composite materials. In the second part, a family of imidazolium-based ILs with the same cation, 1-butyl-3-methylimidazolium [BMIM], and seven different anions were selected and incorporated into a well-known MOF, CuBTC (HKUST-1). Effects of interionic interactions in ILs on the extent of interactions between IL and MOF were investigated. The results showed that ILs mostly interact with the open metal sites of CuBTC, and extent of these interactions depends strongly on the IL structure. Consequences of these interactions on the thermal stability limits and adsorption performance of the IL/MOF composites were examined. Results exhibited that interionic interaction in ILs which can be probed spectroscopically with C2-H vibration frequency is the dominant factor in determining the extent of interactions between IL/MOF. In the last part of the thesis, the influence of methylation on the C2 position of an imidazolium type IL ([BMIM][PF6]) was investigated. Results showed that methylation in ILs affects the interactions between IL and MOF and results in improvements in gas separation performance. Results provided in this thesis study can help to systematically design IL/MOF pairs by selecting a proper IL depending on the desired application.