Selective Gas Adsorption in One-Dimensional, Flexible Cu^II Coordination Polymers with Polar Units

Introducing polar Cu−PF 6 parts into a coordination framework will open new routes in the fabrication of high-performance and/or novel functional porous materials. We have designed and synthesized the one-dimensional Cu II coordination polymer [Cu(PF 6 ) 2 (bpetha) 2 ] n ( 1 ), with weak and flexible Cu−PF 6 parts. 1 shows the property of highly selective adsorption for CO 2 and C 2 H 2 gases, which interact with the F atoms of the polar Cu−PF 6 parts. Crystallographic characterization of [Cu(PF 6 ) 2 (4-mepy) 4 ] ( 2 ) with a basic [Cu(PF 6 ) 2 (pyridine) 4 ] structure indicates that 2 forms weak Cu−PF 6 bonds at its axial sites and the polarity of the surface in 2 is higher than that in α-[Ni(NCS) 2 (4-mepy) 4 ]. The axial ligand-exchanged frameworks, [Cu(PF 6 ) 1.4 (BF 4 ) 0.6 (bpetha) 2 ] n ( 3 ) and {[Cu(bpetha) 2 (DMF) 2 ]·2PF 6 } n ( 4 ), enable us to control the onset pressure and maximum adsorption amount for targeted CO 2 gases, showing the first case of finely controlled adsorption properties using one-dimensional porous coordination polymers.