Release of the Narrow-Channel Lock in Porous Crystals for Direct Acetylene Purification

Acetylene (C 2 H 2 ) is an essential chemical feedstock, yet removing carbon dioxide (CO 2 ) impurities in a single step remains a formidable challenge due to their nearly identical molecular sizes and boiling points. Here, we present that by releasing a “narrow-channel lock” through functional-group modulation, a porous crystal ( NTU-87 ) overcomes this limitation. The parent framework NTU-87-NH 2 contains isolated nanopockets locked by – NH 2 groups, exhibiting negligible adsorption difference between CO 2 and C 2 H 2 (2.9 cm 3 g –1 at 0.5 bar, 298 K). Removing these groups transforms the structure into NTU-87 with a ball-neck channel, markedly reversing the adsorption preference and amplifying the difference to 15.6 cm 3 g –1 . Breakthrough experiments confirm that NTU-87 binds CO 2 more strongly than C 2 H 2, enabling single-step production of pure C 2 H 2 from CO 2 /C 2 H 2 mixtures with low regeneration energy. This strategy of unlocking confined pore architectures establishes functional-group regulation as a general route to high-performance gas purification.