Multifunctional Microporous MOFs Exhibiting Gas/Hydrocarbon Adsorption Selectivity, Separation Capability and Three-Dimensional Magnetic Ordering

摘要

Microporous materials [M_3(HCOO)_6] · DMF (M = Mn, Co, Ni) were synthesized solvothermally and structurally characterized by single crystal and powder X-ray diffraction methods. The metal network exhibits diamondoid connectivity and the overall framework gives rise to zigzag channels along the b axis where guest dimethylformamide molecules reside. The effective pore size of these channels is ～5-6 A. The materials feature high thermal stability and permanent porosity with relatively small pore diameters which are attributed to the extensive strong dative bonding between the metal centers and formate molecules. The title compounds exhibit interesting multi-fold gas adsorption and magnetic properties. The adsorption study of a series of alcohols, aromatics, and linear hydrocarbons revealed strong control of the adsorbent channel structures on their adsorption capacity and selectivity. The study also indicated possibility of using these materials for separation of close boiling chemicals (e.g., ethylbenzene and p-xylene) via pressure swing adsorption (PSA) process and molecules with different diffusion parameters via kinetic-based process. Three-dimensional spontaneous magnetic ordering was found in all three network structures investigated and at ground states they behave somewhat like soft magnets.