Abstract
Annular tetranuclear cluster based metal-organic frameworks (MOFs) have displayed unique advantages in gas adsorption and separation due to their highly connected robust architectures. Herein, two novel heterometallic tetranuclear motifs, [Y(2)Cd(2)(μ(3)-O)(2)(COO)(8)(H(2)O)(2)] and [Y(2)In(2)(μ(3)-O)(2)(μ(2)-O)(2)(COO)(8)(H(2)O)(2)], were successfully explored, which were further extended by 1,3,5-tris(4-carboxyphenyl)benzene (H(3)BTB) tritopic linker to give isostructural MOFs (SNNU-326 and -327). SNNU-326 and -327 both exhibit the abilities to remove impurities (C(2)-hydrocarbons and CO(2)) in natural gas (NG) and excellent CH(4) storage capacities at high pressures. SNNU-326 shows better CH(4) purification and storage performance than SNNU-327 owing to different framework charges, in which only one counter ion is needed in SNNU-326 but two of them are necessary for SNNU-327, thus resulting in an obvious decrease of surface area. Dynamic breakthrough experiments demonstrate that SNNU-326 can effectively separate CH(4) from equimolar C(2)H(2)/CH(4), C(2)H(4)/CH(4), C(2)H(6)/CH(4), and CO(2)/CH(4) mixtures with breakthrough interval times of about 40.6, 35.1, 54.2, and 10.2 min g(-1) (273 K, 1 bar, 2 mL min(-1)), respectively. At the same time, SNNU-326 exhibits excellent CH(4) storage capability with total and working uptakes of 154.3 cm(3) (STP) cm(-3) (80 bar) and 103.4 cm(3) (STP) cm(-3) (5-65 bar) at 273 K on account of the collaborative impacts of adequate apertures, high surface areas, and multiple open metal sites.