Selective CO2 adsorption and theoretical simulation of a stable Co(ii)-based metal–organic framework with tunable crystal size

Abstract

A three-fold interpenetrated metal–organic framework [Co₂(OBA)₄(PTD)·3DMF·CH₃CH₂OH·5H₂O]_n (1) has been synthesized by utilizing 4,4′-oxybis(benzoic acid) (H₂OBA) as the linker, 6-(pyridin-4-yl)-1,3,5-triazine-2,4-diamine (PTD) as the ligand, and CoCl₂·6H₂O via solvothermal method. Compound 1 exhibits not only a high uptake capacity for CO₂ molecules with an estimated high sorption heat (50.6 kJ mol⁻¹ at zero loading), but also a significant selective adsorption of CO₂ over CH₄, which may be ascribed to the presence of proper-sized pores with high polarity, amine groups and triazine rings of PTD linker decorating the pores. Meanwhile, the Grand Canonical Monte Carlo (GCMC) simulations of CO₂ adsorption of compound 1 demonstrate that CO₂ molecules are preferentially adsorbed around the PTD ligands. Furthermore, complex 1 displays a relatively high adsorption capacity of H₂ (101.7 cm³ g⁻¹ at 1 bar) under 77 K.