Inverse selectivity for CO2 over C2H2 in an interdigitated coordination polymer

The separation of carbon dioxide (CO₂) from acetylene (C₂H₂) is crucial but highly challenging due to their similar molecular dimensions and physicochemical properties. In contrast to C₂H₂-selective adsorbents, CO₂-selective adsorption strategy substantially reduces energy consumption by eliminating the need for additional C₂H₂ desorption steps. However, the development of CO₂-selective adsorbents capable of reversing C₂H₂/CO₂ separation remains limited and requires further exploration. Herein, we report a porous coordination polymer, [Cu(5-NH₂-ipa)(pia)], featuring an interdigitated structure with one-dimensional corrugated channels to directly purify C₂H₂. Adsorption results indicate that at 298 K and 1.0 bar, [Cu(5-NH₂-ipa)(pia)] exhibits a CO₂/C₂H₂ 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 CO₂, enabling preferential CO₂ 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 CO₂ can be directly obtained from CO₂ and C₂H₂ mixtures. This work paves the way for the future development of advanced porous materials and inspires their use for CO₂-selective capture from C₂H₂.