Metal–Organic Framework Based Hydrogen-Bonding Nanotrap for Efficient Acetylene Storage and Separation

Abstract

The removal of carbon dioxide (CO 2 ) from acetylene (C 2 H 2 ) is a critical industrial process for manufacturing high-purity C 2 H 2 . However, it remains challenging to address the tradeoff between adsorption capacity and selectivity, on account of their similar physical properties and molecular sizes. To overcome this difficulty, here we report a novel strategy involving the regulation of a hydrogen-bonding nanotrap on the pore surface to promote the separation of C 2 H 2 /CO 2 mixtures in three isostructural metal–organic frameworks (MOFs, named MIL-160, CAU-10H, and CAU-23, respectively). Among them, MIL-160, which has abundant hydrogen-bonding acceptors as nanotraps, can selectively capture acetylene molecules and demonstrates an ultrahigh C 2 H 2 storage capacity (191 cm 3 g –1, or 213 cm 3 cm –3 ) but much less CO 2 uptake (90 cm 3 g –1 ) under ambient conditions. The C 2 H 2 adsorption amount of MIL-160 is remarkably higher than those for the other two isostructural MOFs (86 and 119 cm 3 g –1 for CAU-10H and CAU-23, respectively) under the same conditions. More importantly, both simulation and experimental breakthrough results show that MIL-160 sets a new benchmark for equimolar C 2 H 2 /CO 2 separation in terms of the separation potential (Δ q break = 5.02 mol/kg) and C 2 H 2 productivity (6.8 mol/kg). In addition, in situ FT-IR experiments and computational modeling further reveal that the unique host–guest multiple hydrogen-bonding interaction between the nanotrap and C 2 H 2 is the key factor for achieving the extraordinary acetylene storage capacity and superior C 2 H 2 /CO 2 selectivity. This work provides a novel and powerful approach to address the tradeoff of this extremely challenging gas separation.