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

Abstract

One-step separation of C2H4from ternary C2H2/C2H4/C2H6hydrocarbon 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 C2H4over C2H2and C2H6. The 4,6-connectedfscframework of CuTiF6-TPPY exhibits semi–cage-like one-dimensional channels sustained by porphyrin rings and TiF62−pillars, which demonstrates the noticeably enhanced adsorption of C2H2and C2H6over 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 C2H4in the framework are less marked.

One Atom Can Make All the Difference: Gas-Induced Phase Transformations in Bisimidazole-Linked Diamondoid Coordination Networks

“…The design and performance fine-tuning of sorbents for gas storage technologies for gaseous energy sources , remain a challenge. In the context of gas separations, a new generation of ultramicroporous physisorbents offers advantages over chemisorbents due to lower energy requirements for sorbent recycling. − For gas storage using physisorbents, flexible metal–organic materials (FMOMs), or soft porous crystals, − have emerged as attractive alternatives to rigid sorbents for storage applications since they can offer enhanced working capacity. , FMOMs have been developed in the past two decades, and their sorption profiles tend to be different from rigid coordination networks (CNs), ,,, with isotherm types that occur because of dynamic behavior. These FMOMs can respond to external stimuli such as light, temperature, mechanical pressure, and guest molecules, making them of interest for gas separation, catalysis, drug delivery, and sensing in addition to gas storage.…”

Design of Olefin-Phobic Zeolites for Efficient Ethane and Ethylene Separation

“…Such materials may allow the preferential adsorption of C 2 H 6 having a slightly larger polarizability than C 2 H 4 . Recently, some novel microporous organometallic and organic materials, including metal–organic frameworks (MOFs), − zeolite imidazolate frameworks (ZIFs), − hydrogen-bonded organic frameworks (HOFs), − and porous organic cages (POCs), have been reported to preferentially adsorb C 2 H 6 over C 2 H 4 . Although these materials exhibit a wide range of structural and adsorption properties, several important design principles can be drawn for C 2 H 6 -selective adsorbents.…”

“…First, the adsorbents must have no open metal sites (Lewis acids) that can strongly interact with the π-electrons of C 2 H 4 (Lewis base). Second, the presence of Lewis basic moieties, such as aromatics − ,− ,− , and heteroatoms (N, ,− , O, ,,, and F), is often beneficial for improving the C 2 H 6 /C 2 H 4 selectivity. This can be explained by the fact that C 2 H 6 has six slightly polarized C δ− –H δ+ bonds and the basic moieties can interact via weak C–H···π, − ,− , C–H···N, ,,, C–H···O, ,, and C–H···F hydrogen bonds.…”

“…Second, the presence of Lewis basic moieties, such as aromatics − ,− ,− , and heteroatoms (N, ,− , O, ,,, and F), is often beneficial for improving the C 2 H 6 /C 2 H 4 selectivity. This can be explained by the fact that C 2 H 6 has six slightly polarized C δ− –H δ+ bonds and the basic moieties can interact via weak C–H···π, − ,− , C–H···N, ,,, C–H···O, ,, and C–H···F hydrogen bonds. In particular, due to strong C–H···O interactions, Fe­(O 2 )­(dobdc) with iron­(III)-peroxo moieties has been reported to exhibit remarkably higher C 2 H 6 /C 2 H 4 selectivity (4.4) than other C 2 H 6 -selective adsorbents (1.3–2.96). ,− …”

“…First, the adsorbents must have no open metal sites (Lewis acids) that can strongly interact with the π-electrons of C 2 H 4 (Lewis base). Second, the presence of Lewis basic moieties, such as aromatics [14][15][16][17][18][19][21][22][23][25][26][27][28]30 and heteroatoms (N, 12,[18][19][20]24 O, 13,18,27,29 and F 19 ), is often beneficial for improving the C 2 H 6 /C 2 H 4 selectivity. This can be explained by the fact that C 2 H 6 has six slightly polarized C δ− −H δ+ bonds and the basic moieties can interact via weak C−H•••π, [14][15][16][17][18][19][20][21][22][23][25][26][27][28]30 C−H••• N, 12,18,19,24 C−H•••O, 13,18,27 Although recently developed organometallic and organic adsorbents offer considerable flexibility in material design, there are still general concerns ab...…”