Daniel Hedbom: Adsorbent Characteristics and Pollutant Capture in Metal-Organic Framework Design

Abstract

As our understanding of the environmental impact of anthropogenic pollution has grown, so too, has the need for strategies to capture pollutants from often complex environments, such as the Earth's atmosphere or water. One possible sorbent for such applications is the metal-organic framework or MOF. In this thesis, we explore and attempt to characterise and summarise the outcomes of various approaches in the design of MOFs, as well as a few theoretical and practical technical applications.

Novel materials involved were, with the organic linker TBAPy (4,4’,4”,4”’- (pyrene-1,3,6,8 tetrayl)-tetrabenzoic acid): Ga-TBAPy, V-TBAPy, Hf-TBAPy, Yb-TBAPy, Tm-TBAPy and Ce-TBAPy.  With the TCPB (4’,5’-bis(4-carboxyphenyl)-[1,1’:2’,1”-terphenyl]-4,4”-dicarboxylic acid) organic linker: Ga-TCPB and V-TCPB.

TBAPy MOFS such as Ga-TBAPy were found to have a relatively high SF6 uptake at 100 kPa (3.5 mmol/g, 298 K) and 1.33 mmol/g at 10 kPa, compared to the TCPB-MOFs which had a significantly higher uptake at 10 kPa (2.26 mmol/g, 298 K) and 2.95 mmol/g at 100 kPa.  This low-pressure uptake in TCPB-MOFs, combined with a very low uptake of N2 under the same conditions, resulted in IAST selectivities of as high as 418 in Ga-TCPB.

MOFs based on other strategies, UU-200 (or Bi-H3BTC (benzene-1,3,5-tricarb oxylic acid)) and UiO-67-F2 (Zr-3,3'-difluoro-[1,1'-biphenyl]-4,4'-dicarboxyl -ic acid), also showed interesting characteristics.

UU-200 was found to have a promising CO2 uptake of 2 mmol/g (293 K, 100 kPa), and a high low-pressure uptake at 0.82 mmol/g (15 kPa 298 K). UU-200 was also markedly different than other examined MOFs in the sense that it is a narrow-pore material.

UiO-67-F2 was found to have a very high uptake of SF6 at 5.2 mmol/g (298 K, 100 kPa), it may be an interesting sorbent for SF6 storage. The uptake of perfluorinated octanoic acid (PFOA), from aqueous solution was also investigated in the case of UiO-67-F2. Under what can be considered standard benchmarking conditions (298 K, 1 mgMOF/mlSuspension, 1000 mgPFOA/mlH2O, it was found that UiO-67-F2 had a very high uptake 928 mgPFOA /gMOF in addition, the saturation uptake at 1 700 mg/g (at 3200 mgPFOA /mlH2O which is among the highest uptakes currently available in published literature.