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Methane (CH 4) purification using energy-efficient separation technology is important for the economic and safety of natural gas refining. Meanwhile, the common impurity acetylene (C 2 H 2) was also served as raw material to produce various organic products, therefore the highly efficient purification of CH 4 and C 2 H 2 are very important and challenging. Herein, we demonstrate the separation ability of HOF-16 for C 2 H 2 /CH 4 and CO 2 /CH 4 mixtures in detail. HOF-16 has a potential affinity for C 2 H 2 capture, resulting from the exposed free –COOH sites in the suitable pore channel. Gas sorption isotherms reveal that HOF-16a creates a high C 2 H 2 /CH 4 uptake ratio of 7.9 at 298 K and 1 bar, resulting in a C 2 H 2 /CH 4 separation selectivity of 107 (50/50, v/v) under ambient conditions, which is a record value among HOFs and even exceeds many MOFs. Theoretical calculations confirm that the free –COOH sites in the HOF-16a channel provide additional interactions for the C 2 H 2 molecules. Dynamic breakthrough experiments indicate that C 2 H 2 could be highly selective removed from C 2 H 2 /CH 4 (1/99, v/v) mixture. Combined with the low isosteric heat of adsorption (Q st), HOF-16a can efficiently extract C 2 H 2 from the adsorption bed and purify CH 4 into high purity (>99.9%) with low energy consumption. HOF-16 for separating C 2 H 2 /CH 4 gas mixture into high purity gas. [Display omitted] • HOF-16 was synthesized and has free –COOH after activation. • Activated phase HOF-16a has a suitable pore size and a polar pore environment. • HOF-16a exhibits C 2 H 2 /CH 4 selectivity of 107 and C 2 H 2 /CH 4 uptake ratio of 6.9. • HOF-16a can efficiently separate C 2 H 2 /CH 4 mixture in one sorption-desorption cycle. [ABSTRACT FROM AUTHOR]