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.