Selective Gas Adsorption in One-Dimensional, Flexible CuII Coordination Polymers with Polar Units

Introducing polar Cu-PF6 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(PF6)(2)(bpetha)(2)](n) (1), with weak and flexible Cu-PF6 parts. 1 shows the property of highly selective adsorption for CO2 and C2H2 gases, which interact with the F atoms of the polar Cu-PF6 parts. Crystallographic characterization of [Cu(PF6)(2)(4-mepy)(4)] (2) with a basic [Cu(PF6)(2)(pyridine)(4)] structure indicates that 2 forms weak Cu-PF6 bonds at its axial sites and the polarity of the surface in 2 is higher than that in alpha-[Ni(NCS)(2)(4-mepy)(4)]. The axial ligand-exchanged frameworks, [Cu(PF6)(1.4)(BF4)(0.6)(bpetha)(2)](n) (3) and {[Cu(bpetha)(2)(DMF)(2)]center dot 2PF(6)}(n) (4), enable us to control the onset pressure and maximum adsorption amount for targeted CO2 gases, showing the first case of finely controlled adsorption properties using one-dimensional porous coordination polymers.