From design to application: the synthesis of metal-organic frameworks (MOFS) with an environmentally benign solvent for applications in environmental protection

Zhang, Jinfeng (2017) From design to application: the synthesis of metal-organic frameworks (MOFS) with an environmentally benign solvent for applications in environmental protection. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (17MB)

Abstract

Metal-organic frameworks (MOFs) are a series of porous materials made of wellorganized inorganic metal nodes linked via organic ligands (linkers). MOFs have gained particular attention due to their applications in gas adsorption and separation, selective sorption of harmful chemicals, catalysis, energy, sensing, bioscience, and electronics. The thesis will focus on two different aspects of MOFs. Briefly, in the first portion of the thesis, a less-toxic solvent than N,N-dimethylformamide (DMF) can be used to make MOFs will be demonstrated. In the latter portion of the thesis, my efforts to incorporate organic moieties into MOFs for sulfur dioxide sequestration will be described. With regard to the use of less-toxic solvents, it should be noted that with notable exceptions (e.g., mechanochemical, water-based, and electrochemical), the synthesis of MOFs is often carried out at elevated temperature using DMF or N,Ndiethylformamide (DEF) as the solvent. However, the industrial-scale synthesis of MOFs from DMF/DEF may generate significant amounts of DMF waste, which can exhibit reprotoxicity and end-of-life issues associated with the formation of NOx upon incineration. With the introduction of the Registration, Evaluation and Authorization of Chemicals (REACH) legislation in the European Union, there is a growing trend towards safer production and use of chemicals by industry. As such, it is crucial to develop green/sustainable methods of synthesizing MOFs. Dihydrolevoglucosenone (Cyrene), a green bioderived solvent from waste cellulose, was applied to the synthesis of MOFs. The MOF, HKUST-1, exhibited a larger Brunauer–Emmett–Teller (BET) surface area than HKUST-1 synthesized with DMF. Four additional archetypal MOFs were also synthesized to verify the universal application of Cyrene in the synthesis of MOFs. However, their BET surface areas were lower than DMF-made MOFs. It was observed that an aldol-condensation product of two Cyrene molecules, in addition to Cyrene trapped within the pores, were responsible for the lower-than expected surface areas. The use of Cyrene has led to a series of design principles that eliminate the need for problematic solvents such as DMF and can be applied to the synthesis of a wide range of MOFs. With regard to sulfur dioxide sequestration, it should be noted that sulfur dioxide, a colorless gas belonging to SOx family, yields detrimental effects via inhalation or absorption. Since MOFs are ideal sorbents for toxic gases, in Chapter 3, I will continue along the theme of reprotoxicity and end-of-life issues by designing MOFs which have the potential to chemically react with sulfur dioxide. Unlike the de novo synthetic pathways in the Chapter 2, the Chapter 3 will demonstrate how solvent-assisted linker exchange (SALE) and solvent-assisted linker incorporation (SALI) can be used to make MOFs with the ideal functionalities for sulfur dioxide sequestration. In Chapter 3, the main focus of the work was to introduce the butadiene functional groups into different MOFs, namely UiO-66, UiO-66-MA (muconic-acid-functionalized UiO-66), MOF-808, MOF-808-BS (butadiene-sulfone-functionalized MOF-808) and MOF-808-BD (butadiene-functionalized MOF-808), the SALI method was vitalized to determine if the butadiene group could undergo a cheletropic reaction in the presence of sulfur dioxide inside the MOF. All MOFs were exposed to a constant flow of sulfur dioxide, the UiO-66-MA was observed to take up three times more sulfur dioxide than the unfunctionalized parent UiO-66. For the MOF-808 series, surprisingly, the unfuctionalized MOF-808 was able to absorb more than two times the sulfur dioxide than MOF-808-BD, and five times higher than MOF-808-BS, respectively. This suggests that the terminal waters and hydroxide groups are responsible for the enhanced uptake. Despite the improved uptake of sulfur dioxide in UiO-66-MA and MOF-808, nuclear magnetic resonance (NMR) and infrared (IR) data indicate that no chemical change occurred to the butadiene-functionalized group, which suggests that a cheletropic reaction did not occur.

Actions (login required)

View Item