Three Robust Isoreticular Metal-Organic Frameworks with High-Performance Selective CO 2 Capture and Separation.

Based on the hard-soft acid base (HSAB) theory, three robust isoreticular metal-organic frameworks (MOFs) with nia topology were successfully synthesized by solvothermal reaction {[In ₃ O(BHB)(H ₂ O) ₃ ]NO ₃ ·3DMA ( JLU-MOF110(In) ), [Fe ₃ O(BHB)(H ₂ O) ₃ ]NO ₃ ( JLU-MOF110(Fe) ), and [Fe ₂ NiO(BHB)(H ₂ O) ₃ ] ( JLU-MOF110(FeNi) ) (DMA = N , N -dimethylacetamide, H ₆ BHB = 4,4″-benzene-1,3,5-triyl-hexabenzoic acid)}. Both JLU-MOF110(In) and JLU-MOF110(Fe) are cationic frameworks, and their BET surface areas are 301 and 446 m ² /g, respectively. By modification of the components of metal clusters, JLU-MOF110(FeNi) features a neutral framework, and the BET surface area is increased up to 808 m ² /g. All three MOF materials exhibit high chemical and thermal stability. JLU-MOF110(In) remains stable for 24 h at pH values ranging from 1 to 11, while JLU-MOF110(Fe) and JLU-MOF110(FeNi) persist to be stable for 24 h at pH from 1 to 12. JLU-MOF110(In) exhibits thermal stability up to 350 °C, whereas JLU-MOF110(Fe) and JLU-MOF(FeNi) can be stable up to 300 °C. Thanks to the microporous cage-based structure and abundant open metal sites, JLU-MOF110(In) , JLU-MOF110(Fe) , and JLU-MOF110(FeNi) have excellent CO ₂ capture capacity (28.0, 51.5, and 99.6 cm ³ /g, respectively, under 298 K and 1 bar). Interestingly, the ideal adsorption solution theory results show that all three MOFs exhibit high separation selectivity toward CO ₂ over N ₂ (35.2, 43.2, and 43.2 for CO ₂ /N ₂ = 0.15/0.85) and CO ₂ over CH ₄ (14.4, 11.5, and 10.1 for CO ₂ /CH ₄ = 0.5/0.5) at 298 K and 1 bar. Thus, all three MOFs are potential candidates for CO ₂ capture and separation. Among them, JLU-MOF110(FeNi) displays the best separation potential, as revealed by dynamic column breakthrough experiments.