Benchmark C2H2/CO2 Separation in an Ultra‐Microporous Metal–Organic Framework via Copper(I)‐Alkynyl Chemistry.

Separation of acetylene from carbon dioxide remains a daunting challenge because of their very similar molecular sizes and physical properties. We herein report the first example of using copper(I)‐alkynyl chemistry within an ultra‐microporous MOF (CuI@UiO‐66‐(COOH)2) to achieve ultrahigh C2H2/CO2 separation selectivity. The anchored CuI ions on the pore surfaces can specifically and strongly interact with C2H2 molecule through copper(I)‐alkynyl π‐complexation and thus rapidly adsorb large amount of C2H2 at low‐pressure region, while effectively reduce CO2 uptake due to the small pore sizes. This material thus exhibits the record high C2H2/CO2 selectivity of 185 at ambient conditions, significantly higher than the previous benchmark ZJU‐74a (36.5) and ATC‐Cu (53.6). Theoretical calculations reveal that the unique π‐complexation between CuI and C2H2 mainly contributes to the ultra‐strong C2H2 binding affinity and record selectivity. The exceptional separation performance was evidenced by breakthrough experiments for C2H2/CO2 gas mixtures. This work suggests a new perspective to functionalizing MOFs with copper(I)‐alkynyl chemistry for highly selective separation of C2H2 over CO2. [ABSTRACT FROM AUTHOR]