A Microporous Hydrogen-Bonded Organic Framework for the Efficient Capture and Purification of Propylene

Adsorptive separation of propylene/propane (C₃ H₆ /C₃ H₈ ) mixture is desired for its potential energy saving on replacing currently deployed and energy-intensive cryogenic distillation. Realizing efficient C₃ H₆ /C₃ H₈ 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 C₃ H₆ /C₃ H₈ mixtures. Under ambient conditions, HOF-16 shows a significant C₃ H₆ /C₃ H₈ 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.