Overcoming Fundamental Limitations in Adsorbent Design: Alkene Adsorption by Non‐porous Copper(I) Complexes.

Purifying alkenes from alkanes requires cryogenic distillation. This consumes energy equivalent to countries of ca. 5 million people. Replacing distillation with adsorption processes would significantly increase energy efficiency. Trade‐offs between kinetics, selectivity, capacity, and heat of adsorption have prevented production of an optimal adsorbent. We report adsorbents that overcome these trade‐offs. [Cu‐Br]3 and [Cu‐H]3 are air‐stable trinuclear complexes that undergo reversible solid‐state inter‐molecular rearrangements to produce dinuclear [Cu‐Br⋅(alkene)]2 and [Cu‐H⋅(alkene)]2. The reversible solid‐state rearrangement, confirmed in situ using powder X‐ray diffraction, allows adsorbent design trade‐offs to be overcome, coupling low heat of adsorption (−10 to −17 kJ mol−1alkene), high alkene:alkane selectivity (47; 29), and uptake capacity (>2.5 molalkene mol−1Cu3). Most remarkably, [Cu‐H]3 displays fast uptake and regenerates capacity within 10 minutes. [ABSTRACT FROM AUTHOR]