Higher Symmetry Multinuclear Clusters of Metal–Organic Frameworks for Highly Selective CO₂ Capture

Abstract

A new approach of finely tuning multinuclear clusters of metal-organic frameworks (MOFs) through symmetry-upgradingly isoreticular transformation was first presented and a bcu-type MOF, {[Cu₄(μ₄-O)Cl₂(IN)₄][CuCl₂]}_∞ (NJU-Bai35; NJU-Bai for Nanjing University Bai group), with cluster [Cu₄(μ₄-O)Cl₂(COO)₄N₄] of higher symmetry compared to the pristine MOF, was successfully synthesized. The symmetry upgrading implemented on the inorganic part triggers the adjustment of channels in NJU-Bai35 to fit CO₂ molecules, leading to a high CO₂ adsorption capacity (7.20 wt % at ∼0.15 bar and 298 K) and high selectivity of CO₂ over N₂ and CH₄ (275.8 for CO₂/N₂ and 11.6 for CO₂/CH₄) in NJU-Bai35. Breakthrough experiments further confirmed that NJU-Bai35 might be an excellent candidate for CO₂ capture and natural gas purification.