Synergistic binding sites in a hybrid ultramicroporous material for one-step ethylene purification from ternary C ₂ hydrocarbon mixtures

Abstract

One-step separation of C 2 H 4 from ternary C 2 H 2 /C 2 H 4 /C 2 H 6 hydrocarbon mixtures is of great significance in the industry but is challenging due to the similar sizes and physical properties of C 2 H 2 , C 2 H 4 , and C 2 H 6 . Here, we report an anion-pillared hybrid ultramicroporous material, CuTiF 6 -TPPY, that has the ability of selective recognition of C 2 H 4 over C 2 H 2 and C 2 H 6 . The 4,6-connected fsc framework of CuTiF 6 -TPPY exhibits semi–cage-like one-dimensional channels sustained by porphyrin rings and TiF 6 2− pillars, which demonstrates the noticeably enhanced adsorption of C 2 H 2 and C 2 H 6 over C 2 H 4 . Dynamic breakthrough experiments confirm the direct and facile high-purity C 2 H 4 (>99.9%) production from a ternary gas mixture of C 2 H 2 /C 2 H 6 /C 2 H 4 (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 C 2 H 6 ; meanwhile, the polar TiF 6 2− pillars form C–H•••F hydrogen bonding with C 2 H 2 . In contrast, the recognition sites for C 2 H 4 in the framework are less marked.