Synergistic binding sites in a hybrid ultramicroporous material for one-step ethylene purification from ternary C2 hydrocarbon mixtures.

Abstract

One-step separation of C2H4 from ternary C2H2/C2H4/C2H6 hydrocarbon mixtures is of great significance in the industry but is challenging due to the similar sizes and physical properties of C2H2, C2H4, and C2H6. Here, we report an anion-pillared hybrid ultramicroporous material, CuTiF6-TPPY, that has the ability of selective recognition of C2H4 over C2H2 and C2H6. The 4,6-connected fsc framework of CuTiF6-TPPY exhibits semi–cage-like one-dimensional channels sustained by porphyrin rings and TiF62− pillars, which demonstrates the noticeably enhanced adsorption of C2H2 and C2H6 over C2H4. Dynamic breakthrough experiments confirm the direct and facile high-purity C2H4 (>99.9%) production from a ternary gas mixture of C2H2/C2H6/C2H4 (1/9/90, v/v/v) under ambient conditions. Computational studies and in situ infrared reveal that the porphyrin moieties with large π-surfaces form multiple van der Waals interactions with C2H6; meanwhile, the polar TiF62− pillars form C–H•••F hydrogen bonding with C2H2. In contrast, the recognition sites for C2H4 in the framework are less marked.