Host–Guest Interaction Modulation in Porous Coordination Polymers for Inverse Selective CO2/C2H2 Separation

Controlling gas sorption by simple pore modification is important in molecular recognition and industrial separation processes. In particular, it is challenging to realize the inverse selectivity, which reduces the adsorption of a high‐affinity gas and increases the adsorption of a low‐affinity gas. Herein, an “opposite action” strategy is demonstrated for boosting CO2/C2H2 selectivity in porous coordination polymers (PCPs). A precise steric design of channel pores using an amino group as an additional interacting site enabled the synergetic increase in CO2 adsorption while suppressing the C2H2 adsorption. Based on this strategy, two new ultramicroporous PCP physisorbents that are isostructural were synthesised. They exhibited the highest CO2 uptake and CO2/C2H2 volume uptake ratio at 298 K. Origin of this specific selectivity was verified by detailed density functional theory calculations. The breakthrough separation performances with remarkable stability and recyclability of both the PCPs render them relevant materials for C2H2 purification from CO2/C2H2 mixtures. Boosting inverse CO2/C2H2 selectivity is achieved through precise steric design of amino groups in the pore surface to provide enhanced CO2–framework interactions and suppressed C2H2 adsorption. The obtained two new porous coordination polymers (PCPs) exhibit high CO2 uptake and strong separation performance for one‐step C2H2 purification at room temperature, which can be considered as new physisorbents with this specific inverse selectivity.