RESUMEN
Construction of thermally and chemically robust metal-organic frameworks (MOFs) is highly desirable for postcombustion CO2 capture from flue gas containing water vapor and other acidic gases. Here we report a strategy based on appending amino groups to the triazolate linkers of MOFs to achieve exceptional chemical stability against aqueous, acidic, and basic conditions. These MOFs exhibit not only CO2/N2 thermodynamic adsorption selectivity as high as 120 but also CO2/H2O kinetic adsorption selectivity up to 70, featuring distinct adsorptive sites at the channel center for CO2 and at the corner for H2O, respectively. The best performing MOF in this series features low regeneration energy, high CO2 capture utility under humid conditions, and decent cycling performance for mimic flue gas.
RESUMEN
Metal-organic frameworks (MOFs) is a promising class of sorbent materials for swing adsorption gas separation. However, although sorption kinetics plays a major role in column breakthrough experiments, it is rarely studied with MOF materials. This is largely because the synthesis of uniform yet separation-relevant MOFs is a challenging task. Here, we report a dual-modulation approach for the synthesis of well-defined Mg-MOF-74 hexagonal rods with an extremely uniform size distribution (polydispersity index = 1.02). Through epitaxial growth and wet chemical etching, uniform hollow Ni-MOF-74 with plate-shaped caps were obtained. CO2 adsorption kinetic study shows that hollow Ni-MOF-74 exhibits 54% faster diffusion rate compared to solid Ni-MOF-74 due to a shortened diffusion length, despite their identical CO2 uptake capacity. This has led to a 21% extension of column breakthrough time during CO2/N2 separation under identical conditions.