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

Here, we present a new ultramicroporous Cu paddlewheel based MOF. This ultramicroporous MOF has most of the features such as porosity (BET surface area = 945 m/g), CO capacity (3.5 mmol/g at ambient temperature and pressure), CO/N selectivity (sCO/N = 250), and fast CO diffusion kinetics ( D = 2.25 × 10 m/s), comparable to some of the other high-performing ultramicroporous MOFs, with strong binding sites. Typically, such MOFs exhibit strong CO-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 CO-framework interaction (HOA = 26 kJ/mol). Using periodic DFT, we have probed this counterintuitive observation.