The separation of ethylene (C2H4) from C2 hydrocarbons is considered as one of the most difficult and important processes in the petrochemical industry. Heat-driven cryogenic distillation is still widely used in the C2 hydrocarbons separation realms, which is an energy intensive process and takes up immense space. In response to a greener, more energy-efficient sustainable development, we successfully synthesized a multifunction microporous Mg-based MOF [Mg2(TCPE)­(μ2-OH2)­(DMA)2]·solvents (NUM-9) with C2H6/C2H2 selectivity based on a physical adsorption mechanism, and with outstanding stability; especially, it is stable up to 500 °C under an air atmosphere. NUM-9a (activated NUM-9) shows good performances in the separation of C2H6/C2H2 from raw ethylene gases. In addition, its actual separation potential is also examined by IAST and dynamic column breakthrough experiments. GCMC calculation results indicate that the unique structure of NUM-9a is primarily conducive to the selective adsorption of C2H6 and C2H2. More importantly, compared with C2H4, NUM-9a prefers to selectively adsorb C2H6 and C2H2 simultaneously, which makes NUM-9a as a sorbent have the capacity to separate C2H4 from C2 hydrocarbon mixtures under mild conditions through a greener and energy-efficient separation strategy.

As a new type of porous material, metal–organic frameworks (MOFs) have been widely studied in gas adsorption and separation, especially in C2 hydrocarbons. Considering the stronger interaction between the unsaturated molecules and the metal sites, and the smaller molecular size of unsaturated molecules, the usual relationship of affinities and adsorption capacities among C2 hydrocarbons in most common MOFs is C2H2 > C2H4 > C2H6. Herein, a unique microporous metal–organic framework, NUM-7a (activated NUM-7), with a completely reversed adsorption relationship for C2 hydrocarbons (C2H6 > C2H4 > C2H2) has been successfully synthesized, which breaks the traditional concept of the adsorption relationship of MOFs for C2 hydrocarbons. Based on this unique adsorption relationship, a green and simple one-step separation purification for a large amount of C2H4 can be expected to be achieved through the selective adsorption of C2H6. In addition, NUM-7a also shows good selectivities in C2H2/CO2 and CO2/CH4.

The propane (C 3 H 8 )-trapping adsorption behavior is considered as a potential performance to directly produce highpurity propylene (C 3 H 6 ). Herein, we report an ultramicroporous Mn-based metal−organic framework (NUM-7) with a reverse C 3 H 8 -selective behavior in the low-pressure area. The pore structure of this material possesses more electronegative aromatic benzene rings for the stronger binding affinity to C 3 H 8 , and the material shows outstanding reverse ideal adsorbed solution theory (IAST) selectivity values. Single-component sorption isotherms preliminarily show the reverse adsorption behavior in the lowpressure part, and the moderate heat of adsorption further confirms this performance and exhibits less energy consumption for regeneration. In addition, the purification effect for the C 3 H 8 / C 3 H 6 mixture is evaluated by the IAST selectivity and transient breakthrough curves, and the GCMC calculation results reveal that the fascinating C 3 H 8 -trapping behavior mainly depends on the multiple C−H•••π interactions. Moreover, because C 3 H 6 is the desired target product, the interesting C 3 H 8 -selective adsorption behavior of NUM-7 may provide its potential for one-step purification of C 3 H 6 , and this work can provide the method of developing C 3 H 8 -selective materials for the purification of C 3 H 6 .

Highly selective separation and purification of acetylene (C2H2) from ethylene (C2H4) and carbon dioxide (CO2) are daunting challenges in light of their similar molecule sizes and physical properties. Herein, we report a two-dimensional (2D) stable metal–organic framework (MOF), NUM-11 ([Cu­(Hmpba)2]·1.5DMF) (H2mpba = 4-(3,5-dimethyl-1H-pyrazol-4-yl)­benzoic acid), with sql topology, stacked together through π–π interactions for efficient separation of C2H2 from C2H4 and CO2. The 2D-MOF material offers high hydrolytic stability and good purification capacity; especially, it could survive in water for 7 months, even longer. This stable MOF selectively captures C2H2 from mixtures containing C2H4 and CO2, as determined by adsorption isotherms. The ideal adsorbed solution theory selectivity calculations and transient breakthrough experiments were performed to verify the separation capacity. The low isosteric heat of NUM-11a (desolvated NUM-11) (18.24 kJ mol–1 for C2H2) validates the feasibility of adsorbent regeneration with low energy footprint consumption. Furthermore, Grand Canonical Monte Carlo simulations confirmed that the pore surface of the NUM-11 framework enabled preferential binding of C2H2 over C2H4 and CO2 via multiple C–H···O, C–H···π, and C–H···C interactions. This work provides some insights to prepare stable MOF materials toward the purification of C2H2, and the water-stable structure, low isosteric heat, and good cycling stability of NUM-11 make it very promising for practical industrial application.

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