Efficient capture of C2H2 from CO2 and CnH4 by a novel fluorinated anion pillared MOF with flexible molecular sieving effect

The efficient separation of acetylene (C2H2) from carbon dioxide (CO2) and CnH4 (n = 1 and 2) to manufacture high purity C2H2 and recover other light hydrocarbons is technologically important, while posing significant challenges. Herein, we reported a new TiF62− anion (TIFSIX) pillared metal-organic framework (MOF) ZNU-5 (ZNU = Zhejiang Normal University) with ultramicropores for highly selective C2H2 capture with low adsorption heat through gate opening based molecular sieving effect. ZNU-5 takes up a large amount of C2H2 (128.6 cm3/g) at 1.0 bar and 298 K but excludes CO2, CH4, and C2H4. Such high capacity has never been realized in MOFs with molecular sieving. The breakthrough experiments further confirmed the highly selective C2H2 separation performance from multi-component gas mixtures. 3.3, 2.8, and 2.2 mmol/g of C2H2 is captured at ZNU-5 from equimolar C2H2/CO2, C2H2/CO2/CH4, and C2H2/CO2/CH4/C2H4 mixtures, respectively. Furthermore, 2.6, 2.0, and 1.5 mmol/g of > 98% purity C2H2 can be recycled from the desorption process. Combining high working capacity, low adsorption heat, as well as good recyclability, ZNU-5 is promising for C2H2 purification.