The hole story

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.

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

Jinfeng Zhang

Papers

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