Highly selective gas transport channels in mixed matrix membranes fabricated by using water-stable Cu-BTC

Application of metal-organic frameworks (MOFs) in the field of gas separation has been widely explored, however most of the reported MOFs are sensitive to hydrolysis, restricting their applications under practical environments. In this work, Cu-BTC with distinguishing high resistance to hydrolysis was prepared through in situ functionalization with sodium citrate (SC). The obtained Cu-BTC-SC can hold its structure integrity and preserve its original gas adsorption capacity even after 10 days' immersion in water. On this basis, mixed matrix membranes (MMMs) containing different loadings of Cu-BTC-SC in Pebax (R) 1657 were fabricated and applied for CO2/N-2 and CO2/CH4 separation under humid conditions. The MMMs displayed excellent long-term stability towards humidified test conditions as well as improved CO2 separation performance compared with the pristine Pebax (R) 1657 membrane. Specifically, the membrane incorporated with 15 wt% of Cu-BTC-SC demonstrated a CO2 permeance of 1102.5 GPU together with a CO2/N-2 selectivity of 54.8 for the CO2/N-2 mixed gas, and a CO2 permeance of 1069.6 GPU together with a CO2/CH4 selectivity of 32.5 for the CO2/CH4 mixed gas, surpassing the Robeson upper bounds for CO2/N-2 and CO2/CH4 separation. These results demonstrate a potential effective strategy for improving the water stability of MOFs and suggest a promising candidate for the fabrication of high performance membranes for practical large-scale CO2 separation applications.

Automated summary

The study successfully enhanced the water stability of Cu-BTC by adding sodium citrate, leading to improved gas separation performance in CO2/N-2 and CO2/CH4 mixed matrix membranes.