Interlayer Expansion in a Layered Metal-Organic Framework Enhances CO₂ Capture and CO₂ /N₂ Separation

Developing efficient CO₂ adsorbent materials and technologies is significant to reduce the increasing greenhouse gases concentration in the atmosphere. Herein, a layered MOF with a porous kagomé lattice (kgm), which owned three phases (kgm-1, kgm-2, and kgm-3) via interlayer expansion, was evaluated as a promising CO₂ capture and separation material by using grand canonical Monte Carlo simulations. Results showed that the interlayer expansion provided additional pore volume, which played a considerable role in CO₂ adsorption and separation. The CO₂ adsorption capacity and CO₂ /N₂ selectivity followed the sequence kgm-3>kgm-2>kgm-1, and kgm-3 exhibited an excellent CO₂ adsorption capacity of 8.7 mmol g^-1 at 1 bar with a CO₂ /N₂ selectivity of 130.3 at 20 bar and 298 K. Gas distribution analysis showed that CO₂ and N₂ are adsorbed only in the channels in kgm-1, whereas they could be adsorbed between layers in kgm-2 and kgm-3 due to the interlayer expansion. The adsorption heat and interactions between CO₂ and frameworks were analyzed to elucidate the effect of interlayer expansion. Results of this work highlighted that appropriate interlayer expansion can be an effective approach for framework adsorbents to improve CO₂ capture ability and separation performance at the same time.