Pore space partition via secondary metal ions entrapped by pyrimidine hooks: influences on structural flexibility and carbon dioxide capture

Abstract

A new way of pore space partition via secondary metal ions entrapped by pyrimidine hooks is implemented on flexible metal–organic frameworks. The new resulting (3, 4, 6)-connected MOF, HHU-2 (HHU for Hohai University), whose pore space was partitioned by additional metal ions and flexibility was confined under specific pressure and temperature, exhibits promising CO₂ uptake capacity (17.5 wt% at 1 bar and 298 K), strong CO₂ adsorption enthalpy (30.0 kJ mmol⁻¹), and high CO₂ selectivity towards N₂ (47.3 at 298 K). Importantly, this is the first example of simultaneously achieving high CO₂ selectivity as well as high CO₂ uptake capacity in MOFs by flexibility confinement through the introduction of secondary metal sites.