Divergent Kinetic and Thermodynamic Hydration of a Porous Cu(Ⅱ) Coordination Polymer with Exclusive CO_2 Sorption Selectivity

摘要

Selective adsorption and separation of CO_2 are of great importance for different target applications. Metal-organic frameworks (MOFs) represent a promising class of porous materials for this purpose. Here we present a unique MOF material, [Cu(tba)_2]_n (tba = 4-(1H-1,2,4-triazol-1-yl)benzoate), which shows high CO_2 adsorption selectivity over CH_4/H_2/O_2/Ar/N_2 gases (with IAST selectivity of 41-68 at 273 K and 33-51 at 293 K). By using a critical point dryer, the CO_2 molecules can be well sealed in the 1D channels of [Cu(tba)_2]_n to allow a single-crystal X-ray analysis, which reveals the presence of not only C~(δ+)-H...O~(δ-) bonds between the host framework and CO_2 but also quadrupole - quadrupole (CO_2~(δ-)...~(δ+)CO_2) interactions between the CO_2 molecules. Furthermore, [Cu(tba)_2]_n will suffer divergent kinetic and thermodynamic hydration processes to form its isostruc-tural hydrate {[Cu(tba)_2](H_2O)}_n and a mononudear complex [Cu(tba)_2(H_2O)_4] via single-crystal to single-crystal transformations.