Incorporation of multiple supramolecular binding sites into a robust MOF for benchmark one-step ethylene purification.

Abstract

One-step adsorption separation of C₂H₄ from ternary C₂ hydrocarbon mixtures remains an important and challenging goal for petrochemical industry. Current physisorbents either suffer from unsatisfied separation performance, poor stability, or are difficult to scale up. Herein, we report a strategy of constructing multiple supramolecular binding sites in a robust and scalable MOF (Al-PyDC) for highly efficient one-step C₂H₄ purification from ternary mixtures. Owing to suitable pore confinement with multiple supramolecular binding sites, Al-PyDC exhibits one of the highest C₂H₂ and C₂H₆ uptakes and selectivities over C₂H₄ at ambient conditions. The gas binding sites have been visualized by single-crystal X-ray diffraction studies, unveiling that the low-polarity pore surfaces with abundant electronegative N/O sites provide stronger multiple supramolecular interactions with C₂H₂ and C₂H₆ over C₂H₄. Breakthrough experiments showed that polymer-grade C₂H₄ can be separated from ternary mixtures with a maximum productivity of 1.61 mmol g^-1. This material can be prepared from two simple reagents using a green synthesis method with water as the sole solvent, and its synthesis can be easily scaled to multikilogram batches. Al-PyDC achieves an effective combination of benchmark separation performance, high stability/recyclability, green synthesis and easy scalability to address major challenges for industrial one-step C₂H₄ purification.