Efficient One-Step Purification of Methanol-to-Olefin Products Using a Porphyrinyl MOF to Achieve Record C2H4 and C3H6 Productivity

The separation of methanol-to-olefin (MTO) products to obtain high-purity ethylene (C2H4) and propylene (C3H6) is a challenging yet critical task, as these compounds are essential industrial raw materials for polymer synthesis. However, developing adsorbents with high selectivity and productivity for C2H4/C3H6 remains a significant challenge and an urgent necessity. In this study, a porphyrinyl metal–organic framework (MOF), Al-TCPP, was developed for the simultaneous recovery of C3H6 and C2H4 through a one-step adsorption–desorption process. Benefiting from its well-developed microporous structure and abundant N- and O-accessible sites, Al-TCPP demonstrated exceptional adsorption capacities and selectivity for C3H6 and ethane (C2H6) over C2H4 under ambient conditions. The adsorption capacities (in cm3·g–1) reached 162.4 for C3H6 and 118.5 for C2H6 at 298 K and 100 kPa. The ideal adsorbed solution theory (IAST) selectivity values for C3H6/C2H4 and C2H6/C2H4 were 10.1 and 1.8, respectively. Thermodynamic studies and theoretical calculations revealed stronger interactions between C2H6 and C3H6 molecules with the Al-TCPP framework than with C2H4. Systematic breakthrough experiments demonstrated outstanding separation performance for binary C2H6/C2H4 and C3H6/C2H4 mixtures, as well as ternary C3H6/C2H6/C2H4 mixtures, achieving record productivities of 150.2 and 86.5 L·kg–1 for polymer-grade C2H4 (≥99.9%) and C3H6 (≥99.5%), respectively. Notably, the separation performance remained stable under variable flow rates, temperatures, humidities, and multiple adsorption–desorption cycles. Overall, this study highlighted Al-TCPP as a highly competitive adsorbent for addressing the challenges in MTO product separation. Moreover, it offered valuable insights into the design of MOFs with heteroatom-rich accessible sites for efficient separation of low-carbon hydrocarbons.