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.
Keywords: crystal engineering; gas separation; hydrogen-bonded organic frameworks; microporous; propylene.
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