Rational Construction of Ultrahigh Thermal Stable MOF for Efficient Separation of MTO Products and Natural Gas

Considering the important application foundation of propylene (C₃H₆) and ethylene (C₂H₄) production, as well as methane (CH₄), in petrochemical industries, this report comprehensively investigated an innovative MOF material (Zn-BPZ-SA) that was synthesized by 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (H₂BPZ) and squaric acid (H₂SA) for separating methanol-to-olefins (MTO) products (C₃H₆/C₂H₄ mixtures) and natural gas (C₃H₈/C₂H₆/CH₄ mixtures). Zn-BPZ-SA with great resistance toward water and exceptional thermal stability (520 °C), can preferentially adsorb C₃H₈ and C₃H₆ rather than C₂H₆ and C₂H₄, and in particular, reveals high C₃H₆ and C₃H₈ uptakes of 46.6 and 48.0 cm³ g^-1 under the crucial low pressure (10 kPa, 298 K). The experimental and simulated transient breakthroughs for C₃H₆/C₂H₄ binary mixtures and C₃H₈/C₂H₆/CH₄ ternary mixtures demonstrated that the MOF can separate these mixtures with long breakthrough time differences, yielding high-purity (>99.95%) products with high productivities: C₂H₄ (21.9-142.8 L kg^-1) and CH₄ (34.9-73.0 L kg^-1). The excellent separation abilities can be attributed to the rich accessbile O/N and methyl binding sites scattered at the pore surfaces in framework.