Efficient capture of trace acetylene by an ultramicroporous metal−organic framework with purine binding sites

Efficient separation of acetylene (C2H2) from its byproducts, especially CO2, is difficult because of their similar physicochemical properties, including molecular dimensions and boiling point. Herein, we demonstrate trace C2H2 removal from C2H2/CO2 mixtures enabled by a new ultramicroporous metal−organic framework (MOF) adsorbent, IPM-101, which features an optimal pore size of 4 Å (close to the kinetic diameter of C2H2, 3.3 Å) and one-dimensional channels lined by Lewis basic purine groups. Single-component gas adsorption isotherms revealed a clear affinity toward C2H2 versus CO2 at low pressures with a substantial C2H2 uptake of 0.9 mmol g−1 at 3000 ppm and 298 K. Dynamic column breakthrough experiments revealed separation of C2H2 from 1:1 and 1:99 v/v C2H2/CO2 mixtures. IPM?101 exhibits one of the highest dynamic separation selectivity (αAC) values yet reported, 22.5 for 1:1 C2H2/CO2. Computational simulations indicated that the purine moiety was key to the strong C2H2 selectivity thanks to C2H2 selective N···HC≡CH interactions.