Host-Guest Interactions in C2H2/CO2 Discriminative Covalent Organic Framework Probed by Solid-State NMR

Covalent organic frameworks (COF) are promising porous materials for energy-efficient gas separation. However, understanding of the interaction between the host framework and the guest gas molecules, which is crucial for the development of the COF adsorbents, remains insufficient. Here, we look into the host-guest interactions between C2H2/CO2 molecules and a propyl sodium sulfonate group functionalized COF. Gas sorption studies indicate that the synthesized COF, termed Py-Na COF, exhibits C2H2/CO2 discriminative adsorption at ambient temperature. The underlying discriminative mechanism is studied by in situ 23Na solid-state NMR combined with molecular dynamics (MD) and density functional theory (DFT) calculations. The interactions between the C2H2/CO2 molecules and the host sodium ion play an essential role in C2H2/CO2 discrimination in Py-Na COF.