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 (Cu-I@UiO-66-(COOH)(2)) to achieve ultrahigh C2H2/CO2 separation selectivity. The anchored Cu-I ions on the pore surfaces can specifically and strongly interact with C2H2 molecule through copper(I)-alkynyl pi-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 pi-complexation between Cu-I and C2H2 mainly contributes to the ultra-strong C2H2 binding affinity and record selectivity. The exceptional separation performance was evidenced by break-through 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.

Automated summary

By using copper(I)-alkynyl chemistry within an ultra-microporous MOF, the researchers achieved ultrahigh C2H2/CO2 separation selectivity with a record high C2H2/CO2 selectivity of 185. The specific interaction between Cu-I ions and C2H2 through pi-complexation played a key role in the exceptional separation performance. This work suggests a new perspective on functionalizing MOFs for selective separation of C2H2 over CO2.