Chemical Property Change in a Metal-Organic Framework by Fluoro Functionality

A fluorine-functionalized HKUST-1 (HKUST-1-F) has been synthesized by a solvothermal reaction between copper nitrate and a potassium salt of 2-fluoro-1,3,5-benzenetricarboxylic acid (K[H₂BTC-F]). HKUST-1-F shows nearly the same crystal structure as that of UHM-31, a known fluorinated HKUST-1. Because of its reduced surface area, HKUST-1-F takes up smaller amounts of gases (N₂ , H₂ , CO₂ ) than UHM-31 at 1 bar. After a water vapor adsorption measurement at 298 K, HKUST-1-F turned into an unknown structure, based on powder X-ray diffraction analyses. HKUST-1-F could be further functionalized with benzylamine in a postsynthetic modification; the nucleophilic replacement of the F atom in BTC-F with benzylamine in methylene chloride at room temperature took place in a conversion yield of ~38% based on ¹H NMR analyses.