Boosting Adsorption and Selectivity of Acetylene by Nitro Functionalisation in Copper(II)-Based Metal-Organic Frameworks.

Purification and storage of acetylene (CH) are important to many industrial processes. The exploitation of metal-organic framework (MOF) materials to address the balance between selectivity for CH vs carbon dioxide (CO) against maximising uptake of CH has attracted much interest. Herein, we report that the synergy between unsaturated Cu(II) sites and functional groups, fluoro (-F), methyl (-CH), nitro (-NO) in a series of isostructural MOF materials MFM-190(R) that show exceptional adsorption and selectivity of CH. At 298 K, MFM-190(NO) exhibits an CH uptake of 216 cm g (320 cm g at 273 K) at 1.0 bar and a high selectivity for CH/CO (up to ~150 for v/v = 2/1) relevant to that in the industrial cracking stream. Dynamic breakthrough studies validate and confirm the excellent separation of CH/CO by MFM-190(NO) under ambient conditions. In situ neutron powder diffraction reveals the cooperative binding, packing and selectivity of CH by unsaturated Cu(II) sites and free -NO groups.