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

Abstract

The removal of carbon dioxide (CO₂) from acetylene (C₂H₂) is a critical industrial process for manufacturing high-purity C₂H₂. 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 C₂H₂/CO₂ 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 C₂H₂ storage capacity (191 cm³ g^-1, or 213 cm³ cm^-3) but much less CO₂ uptake (90 cm³ g^-1) under ambient conditions. The C₂H₂ adsorption amount of MIL-160 is remarkably higher than those for the other two isostructural MOFs (86 and 119 cm³ 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 C₂H₂/CO₂ separation in terms of the separation potential (Δ<i>q</i>_break = 5.02 mol/kg) and C₂H₂ productivity (6.8 mol/kg). In addition, <i>in situ</i> FT-IR experiments and computational modeling further reveal that the unique host-guest multiple hydrogen-bonding interaction between the nanotrap and C₂H₂ is the key factor for achieving the extraordinary acetylene storage capacity and superior C₂H₂/CO₂ selectivity. This work provides a novel and powerful approach to address the tradeoff of this extremely challenging gas separation.