Adsorptive separation of propylene/propane (C3H6/C3H8) mixture is desired for its potential energy saving on replacing currently deployed and energy‐intensive cryogenic distillation. Realizing efficient C3H6/C3H8 separation in the emerging hydrogen‐bonded organic frameworks (HOFs) is very challenging owing to the lack of functional sites for preferential gas binding. By virtue of crystal engineering, we herein report a functionalized HOF (HOF‐16) with free ‐COOH sites for the efficient separation of C3H6/C3H8 mixtures. Under ambient conditions, HOF‐16 shows a significant C3H6/C3H8 uptake difference (by 76 %) and selectivity (5.4) in contrast to other carboxylic acid‐based HOFs. Modeling studies indicate that free ‐COOH groups together with the suitable pore confinement facilitate the recognition and high‐density packing of gas molecules. The separation performance of HOF‐16 was validated by breakthrough experiments. HOF‐16 is stable towards strong acidity and water.

The development of porous metal−organic framework (MOF) solids displaying efficient separation and purification of acetylene is of cardinal significance but challenging in the chemical industry. Among the reported MOFs for such a purpose, there usually exists an issue associated with trade-off between the uptake capacity and adsorption selectivity. In this work, we employed an N-oxide-functionalized dicarboxylate ligand to successfully construct under suitable solvothermal conditions a dicopper paddlewheel-based MOF featuring two different types of nanocages and rich open oxygen atoms on the channel surface. These structural features endow the material with the promising potential for C 2 H 2 recovery from CO 2 and CH 4 at ambient conditions with impressive adsorption selectivity of C 2 H 2 over CO 2 and CH 4 as well as considerable C 2 H 2 capture capacity, which have been validated by isotherm measurements, ideal adsorbed solution theory calculations, and breakthrough experiments. Furthermore, molecular modeling studies revealed the vital role that the oxygen atoms coming from both N-oxide moieties and carboxylate groups play in selectively recognizing C 2 H 2 over CO 2 and CH 4 . KEYWORDS: metal−organic frameworks, C 2 H 2 separation and purification, C 2 H 2 /CO 2 separation, gas separation, N-oxide

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.

NH3 is the most important gaseous alkaline pollutant, which when accumulated at high concentrations can have a serious impact on animal and human health. More importantly, NH3 emissions will react with acidic pollutant gases to form particulate matter (PM2.5) in the atmosphere, which also poses a huge threat to human activities. The use of adsorbents for NH3 removal from emission sources or air is an urgent issue. However, there are difficulties in the compatibility between high adsorption capacity and recyclability for most conventional adsorbents. In this work, a structural transformation strategy using metal–organic frameworks (MOFs) is proposed for large-scale and recyclable NH3 adsorption. A series of M­(BDC) (M = Cu, Zn, Cd) materials can transform into one-dimensional M­(BDC)­(NH3)2 after NH3 adsorption, resulting in repeatable adsorption capacities of 17.2, 14.1, and 7.4 mmol/g, respectively. These MOFs can be completely regenerated at 250 °C for 80 min with no adsorption capacity loss. Besides, breakthrough and cycle tests indicate that Cu­(BDC) and Zn­(BDC) show good performance in the removal of low concentrations of NH3 from the air. Overall, combining the advantages of high adsorption capacity and recyclability due to the reversible structural transformation, Cu­(BDC) and Zn­(BDC) can be employed as ideal adsorbent candidates for NH3 removal.

Functional nanoporous materials are widely explored for CO2 separation, in particular small-pore aluminosilicate zeolites having “trapdoor” effect. Such effect allows the specific adsorbate to push away the sited cations inside...