Synthesis and Characterization of Highly Fluorinated Hydrophobic Rare–Earth Metal–Organic Frameworks (MOFs)

Abstract

Tuning a material’s hydrophobicity is desirable in several industrial applications, such as hydrocarbon storage, separation, selective CO2 capture, oil spill cleanup, and water purification. The introduction of fluorine into rare-earth (RE) metal–organic frameworks (MOFs) can make them hydrophobic. In this work, the linker bis(trifluoromethyl)terephthalic acid (TTA) was used to make highly fluorinated MOFs. The reaction of the TTA and RE3+ (RE: Y, Gd, or Eu) ions resulted in the primitive cubic structure (pcu) exhibiting RE dimer nodes (RE-TTA-pcu). The crystal structure of the RE-TTA-pcu was obtained. The use of the 2-fluorobenzoic acid in the synthesis resulted in fluorinated hexaclusters in the face-centered cubic (fcu) framework (RE-TTA-fcu), analogous to the UiO-66 MOF. The RE-TTA-fcu has fluorine on the linker as well as in the cluster. The MOFs were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, and contact angle measurements.