Ethylene production from C2 hydrocarbon mixtures through one separation
step is desirable but challenging because of the similar size and
physical properties of acetylene, ethylene, and ethane. Herein, we
report three new isostructural porous coordination networks (NPU-1, NPU-2, NPU-3; NPU represents
Northwestern Polytechnical University) that are sustained by 9-connected
nodes based upon a hexanuclear metal cluster of composition [Mn6(μ3-O)2(CH3COO)3]6+. NPU-1/2/3 exhibit a dual cage
structure that was systematically fine-tuned in terms of cage size
to realize selective adsorption of C2H2 and
C2H6 over C2H4. Dynamic
breakthrough experiments demonstrated that NPU-1 produces
ethylene in >99.9% purity from a three-component gas mixture (1:1:1
C2H2/C2H4/C2H6). Molecular modeling studies revealed that the dual
adsorption preference for C2H2 and C2H6 over C2H4 originates from (a)
strong hydrogen-bonding interactions between electronegative carboxylate
O atoms and C2H2 molecules in one cage and (b)
multiple non-covalent interactions between the organic linkers of
the host network and C2H6 molecules in the second
cage.
One-step adsorptive purification of ethylene (C2H4) from four-component gas mixtures comprising acetylene (C2H2), ethylene (C2H4), ethane (C2H6) and carbon dioxide (CO2) is an unmet challenge in the area of commodity purification. Herein, we report that the ultramicroporous sorbent Zn-atz-oba (H2oba = 4,4-dicarboxyl diphenyl ether; Hatz = 3-amino-1,2,4-triazole) enables selective adsorption of C2H2, C2H6 and CO2 over C2H4 thanks to the binding sites that lie in its undulating pores. Molecular simulations provide insight into the binding sites in Zn-atz-oba that are responsible for coadsorption of C2H2, C2H6 and CO2 over C2H4. Dynamic breakthrough experiments demonstrate that the selective binding exhibited by Zn-atz-oba can produce polymer-grade purity (>99.95%) C2H4 from binary (1:1 for C2H4/C2H6), ternary (1:1:1 for C2H2/C2H4/C2H6) and quaternary (1:1:1:1 for C2H2/C2H4/C2H6/CO2) gas mixtures in a single step.
Herein a strategy is reported for capturing and sensing iodine by strong I ⋅⋅⋅I ⋅⋅⋅I interaction, confined in a metal-organic framework, [Tb(Cu I )(ina) (DMF)] (1) (ina=isonicotinate). As revealed by single-crystal X-ray crystallography, the uptaken I molecules directly contact the {Cu I } chains, virtually forming an electronically polarizable tetraiodide anion (I ) through strong I ⋅⋅⋅I ⋅⋅⋅I interaction. As such, a quasi-copper-iodide layer of {Cu I } with semiconducting characteristics results, leading to a significant enhancement (Δ =10 times) in electrical conductivity over the I -free 1. The effect observed is several orders of magnitude higher than those reported due to iodine⋅⋅⋅aromatic interactions (Δ =10 times) and by interactions between I and a redox-active metal centre (Δ =10 times). The drastic enhancement in electrical conductivity was used to switch on/off an LED bulb, suggesting the possibility of electrically sensing I .
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