Preferential Adsorption of CO2 in an Ultramicroporous MOF with Cavities Lined by Basic Groups and Open-Metal Sites.

Here, we present a new ultramicroporous Cu2 paddlewheel based MOF. This ultramicroporous MOF has most of the features such as porosity (BET surface area = 945 m2/g), CO2 capacity (3.5 mmol/g at ambient temperature and pressure), CO2/N2 selectivity (sCO2/N2 = 250), and fast CO2 diffusion kinetics ( Dc = 2.25 × 10-9 m2/s), comparable to some of the other high-performing ultramicroporous MOFs, with strong binding sites. Typically, such MOFs exhibit strong CO2-framework interactions (evidenced from a heat of adsorption ≥ 38 kJ/mol). However, the MOF explained here, despite having channels lined by the amine and the open-metal sites, possesses only a moderate CO2-framework interaction (HOA = 26 kJ/mol). Using periodic DFT, we have probed this counterintuitive observation.