CO2 adsorption of three isostructural metal–organic frameworks depending on the incorporated highly polarized heterocyclic moieties†
A systematic investigation of CO2 adsorption behavior in three metal–organic frameworks was executed. The three MOFs adopted the same NbO-type structure, except that the organic ligands were grafted with different highly polarized heterocyclic moieties, namely, oxadiazole, thiadiazole, and selenadiazole, respectively. After activation, the three MOF materials showed different surface areas and pore volumes depending on the incorporated heterocyclic rings attached to the organic ligands as well as the MOF's stabilities. Among the three MOF materials, ZJNU-41a exhibited an impressive CO2 uptake capacity of 97.4 cm3 (STP) g−1 at 298 K and 1 atm, which is comparable and even superior to those reported in NbO-type MOFs. In particular, when the molecular dipole of the attached heterocyclic moieties increases, the CO2 uptake also increases, which was further supported by comprehensive quantum chemical calculations. This work demonstrates that the introduction of highly polarized heterocyclic functional groups into frameworks is a promising approach to target porous metal–organic framework materials with improved CO2 adsorption performance.