Browsing by Author "Mah, Roger K"

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    Developing Porous Water Stable Metal Phosphonates for CO2 Capture Applications
    (2016) Mah, Roger K; Shimizu, George; Marriott, Robert; Thangadurai, Venkataraman; Maeda, Kazuyuki
    Porous solid sorbents have emerged as a promising class of materials for CO2 capture applications. A subclass of solid sorbents, metal-organic frameworks (MOFs), has been thoroughly investigated towards implementation into CO2 capture systems, owing to high tailorability from an inherently modular nature. The crux of conventional carboxylate-based MOFs has been stability against hydrolytic cleavage in the presence of elevated temperature and humidity. This thesis investigated the development of water stable phosphonate MOFs using the trigonal 1,3,5-tris(phosphonophenyl)benzene (H6L1) as the ligand coordinated to trivalent and tetravalent metals. The first metal investigated was Sn4+, which required significant efforts towards enhancing crystallinity. An ordered material for SnH2L1 (CALF-28) was achieved through solvothermal reaction followed a humidity exposure step. After the harsh humidity treatment, CALF-28 remained porous albeit with a decreased surface area. The second framework investigated utilized La3+ producing single crystals of LaH3L1 (CALF-29). Upon exposure to mild humidity treatment, CALF-29 decomposed resulting in significant loss of surface area revealing CALF-29 had no stability against hydrolytic cleavage. The final metal investigated with L1 was Zr4+ to produce ZrH2L1 (CALF-31). After repeated exposures to harsh humidity, CALF-31 remained porous with only a minor surface area drop. CALF-28 and CALF-31 were evaluated as potential CO2 capture sorbents and revealed the strengths of solid sorbents against the traditional monoethanolamine benchmark using calculations developed during this work. Finally, coordination of 1,3,5-tris(phosphonobiphenyl)benzene (H6L2) with Zr4+ provided insights into the effect of extending the L1 ligand. From the preliminary results, the potential advantages of H6L2, namely increased functionalization sites to accommodate polarizing groups, were discussed in the context of enhancing the CO2 capture potential of frameworks formed using trigonal trisphosphonates.