Robust Ultramicroporous Metal–Organic Frameworks with Benchmark Affinity for Acetylene

Highly selective separation and/or purification of acetylene from various gas mixtures is a relevant and difficult challenge that currently requires costly and energy-intensive chemisorption processes. Two ultramicroporous metal–organic framework physisorbents, NKMOF-1-M (M=Cu or Ni), offer high hydrolytic stability and benchmark selectivity towards acetylene versus several gases at ambient temperature. The performance of NKMOF-1-M is attributed to their exceptional acetylene binding affinity as revealed by modelling and several experimental studies: in situ single-crystal X-ray diffraction, FTIR, and gas mixture breakthrough tests. NKMOF-1-M exhibit better low-pressure uptake than existing physisorbents and possesses the highest selectivities yet reported for C₂H₂/CO₂ and C₂H₂/CH₄. The performance of NKMOF-1-M is not driven by the same mechanism as current benchmark physisorbents that rely on pore walls lined by inorganic anions.