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

• Published in: Journal of the American Chemical Society Vol. 144; no. 4
• Main Authors: Ye, Yingxiang, Xian, Shikai, Cui, Hui, Tan, Kui, Gong, Lingshan, Liang, Bin, Pham, Tony, Pandey, Haardik, Krishna, Rajamani, Lan, Pui Ching, Forrest, Katherine A., Space, Brian, Thonhauser, Timo, Li, Jing, Ma, Shengqian
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society (ACS) 29.12.2021
• Subjects: Adsorption; Hydrocarbons; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Metal organic frameworks; Mixtures; Molecules
• ISSN: 0002-7863; 1520-5126

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 trade-off 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 hydrogen-bonding nanotrap on the pore surface to promote the separation of C2H2/CO2 mixtures, in three isostructural metal-organic frameworks (MOFs, named as 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 ultra-high 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 the other two isostructural MOFs (86 cm3 g–1 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 (Δqbreak = 5.02 mol/kg) and C2H2 productivity (6.8 mol/kg). In addition, in-situ FT-IR experiments combined with computational modeling further reveal that the unique host-guest multiple hydrogen-bonding interactions between the nanotrap and C2H2 is the key factor for achieving extraordinary acetylene storage capacity and superior C2H2/CO2 selectivity. Furthermore, this work provides a novel and powerful approach to address the trade-off of this extremely challenging gas separation.