Inverse selectivity for CO2 over C2H2 in an interdigitated coordination polymer

The separation of carbon dioxide (CO 2 ) from acetylene (C 2 H 2 ) is crucial but highly challenging due to their similar molecular dimensions and physicochemical properties. In contrast to C 2 H 2 -selective adsorbents, CO 2 -selective adsorption strategy substantially reduces energy consumption by eliminating the need for additional C 2 H 2 desorption steps. However, the development of CO 2 -selective adsorbents capable of reversing C 2 H 2 /CO 2 separation remains limited and requires further exploration. Herein, we report a porous coordination polymer, [Cu(5-NH 2 -ipa)(pia)], featuring an interdigitated structure with one-dimensional corrugated channels to directly purify C 2 H 2 . Adsorption results indicate that at 298 K and 1.0 bar, [Cu(5-NH 2 -ipa)(pia)] exhibits a CO 2 /C 2 H 2 uptake ratio of 2.09 and IAST (Ideal adsorbed solution theory) selectivity of 10.9. It possesses optimally sized pores with an electrostatic potential that is highly complementary to the electrostatic properties of CO 2 , enabling preferential CO 2 adsorption through strong electrostatic interactions and hydrogen bonding. This result is well supported by molecular simulation and theoretical calculations. Furthermore, experimental breakthrough tests demonstrate that high-purity CO 2 can be directly obtained from CO 2 and C 2 H 2 mixtures. This work paves the way for the future development of advanced porous materials and inspires their use for CO 2 -selective capture from C 2 H 2 .