Highly scalable acid-base resistant Cu-Prussian blue metal-organic framework for C₂H₂/C₂H₄, biogas, and flue gas separations

One of the emerging problems plaguing the chemical industry today is the selective capture and separation of gases from their mixtures in an efficient and cost-effective manner. MOFs are new-age physisorbent materials extensively investigated for various gas mixture separations (such as biogas, flue gas, olefin/paraffin etc.); however, face the challenge of separations in a realistic environment. Here, we have investigated one of the Prussian blue analogues (Cu-PSB) to explore its potential as energy-efficient gas separation material. Cu-PSB can easily be scaled up at room temperature from water and is highly robust under harsh acidic, basic environments (pH = 1–11, 6 M HCl, 18 M H₂SO₄), exhibiting excellent separation of C₂H₂/C₂H₄, biogas (CO₂:CH₄ = 50:50), and flue gas (CO₂:N₂ = 15:85) mixtures. The IAST selectivity at ambient conditions (295 K, 50:50 mixture) could reach up to 5.2 for C₂H₂/C₂H₄, 14.7 for CO₂/CH₄, and 60.5 for the CO₂/N₂ (15:85 mixture). Such high C₂H₂ and CO₂ uptake capacity and separation selectivity could be attributed to the synergistic effect of open Cu^II sites and the multiple H-bonding interactions within the functional pore channels of optimal pore size. Further, breakthrough simulation confirmed the complete separations from their binary mixtures, thus proving to be highly useful for the C₂H₂/C₂H₄ separation and CO₂ capture from the bio and post-combustion flue gas mixtures. Cu-PSB was found to be even a more robust framework than ZIF-8 and UiO-66 MOFs.