Ethylene (C2H4) purification from multicomponent mixtures by physical adsorption presents a great challenge in the chemical industry. This work successfully uses the postsynthetic method of crystal transformation in boiling alkaline solution to synthesize a trap‐and‐flow channel crystal (namely NTU‐67), the flow channel of which provides an effective shape‐ and size‐dependent sieving path for linear molecules such as acetylene (C2H2) and carbon dioxide (CO2), while the adjacent channel possesses customized space for efficient molecular trapping. The three‐bladed array of the nanospace enables the crystal to afford a record productivity of C2H4 (121.5 mL g−1, >99.95%) from C2H2/CO2/C2H4 (1/9/90, v/v/v) mixtures in a single adsorption–desorption cycle under humid and dynamic conditions, even at a high temperature of 343 K and wide gas ratio. The molecular‐level insight and mechanism of the cooperative role of the trap‐and‐flow channel, found computationally and observed experimentally, demonstrates a new design philosophy toward extending the application boundaries of porous coordination polymers to further challenging tasks.
Energy-efficient separation of propylene (C 3 H 6 )/ propane (C 3 H 8 ) is in high demand for the chemical industry. However, this process is challenging due to the imperceptible difference in molecular sizes of these gases. Here, we report a continuous water nanotube dedicatedly confined in a Cu 10 O 13based metal−organic framework (MOF) that can exclusively adsorb C 3 H 6 over C 3 H 8 with a record-high selectivity of 1570 (at 1 bar and 298 K) among all the porous materials. Such a high selectivity originates from a new mechanism of initial expansion and subsequent contraction of confined water nanotubes (∼4.5 Å) caused by C 3 H 6 adsorption rather than C 3 H 8 . Such unique response was further confirmed by breakthrough measurements, in which one adsorption/desorption cycle yields each component of the binary mixture high purity (C 3 H 6 : 98.8%; C 3 H 8 : >99.5%) and good C 3 H 6 productivity (1.6 mL mL −1 ). Additionally, benefiting from the high robustness of the framework, the water nanotubes can be facilely recovered by soaking the MOF in water, ensuring long-term use. The molecular insight here demonstrates that the confining strategy opens a new route for expanding the function of MOFs, particularly for the sole recognition from challenging mixtures.
Molecular Trapping
In article number 2203745, Jingui Duan, Susumu Kitagawa, and co‐workers report a trap‐and‐flow channel crystal, where the flow channel provides an effective shape‐ and size‐dependent sieving path for linear acetylene and carbon dioxide, while the flow channel possesses a customized space of efficient molecular trapping, yielding a record productivity of poly‐grade C2H4 from C2H2/CO2/C2H4 mixtures.
Soft nanoporous crystals with structural dynamics are among the most exciting of recently discovered materials. However, designing or controlling this system, which can recognize very similar gases, remains a challenge. Here we report a soft crystal (NTU-68) in which one-dimensional channel opening delicately expands and contracts ~4 Å at elevated temperature. A completely different adsorption model for propane (C3H8: kinetic dominance) and propylene (C3H6: thermodynamic preference) allows sieving of C3H8/C3H6 mixtures at 273 K (10 min·g-1), as well as boosted performance at 298 K (22 min·g-1). This is contrary to the general observation for adsorption separation, the higher the temperature, the lower the efficiency. Gas-loaded in-situ powder X-ray analysis and model calculations reveal that slight pore enlargement in the temperature response provides plausible traffic for C3H6 but remains constriction on C3H8. The finely controlled dynamic systems and efficient molecular recognition provide a new route for design of next-generation sieve materials.
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