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

Acetylene (C2H2) is an essential chemical feedstock, yet removing carbon dioxide (CO2) 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-NH2 contains isolated nanopockets locked by -NH2 groups, exhibiting negligible adsorption difference between CO2 and C2H2 (2.9 cm3 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 cm3 g-1. Breakthrough experiments confirm that NTU-87 binds CO2 more strongly than C2H2, enabling single-step production of pure C2H2 from CO2/C2H2 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.