CO₂adsorption at low pressure over polymers-loaded mesoporous metal organic framework PCN-777: Effect of basic site and porosity on adsorption

Selective capture of CO2 from offgas is highly important for our sustainability, including mitigating global warming. Here, we investigated the CO2 and N2 adsorption under low pressure by using a mesoporous Zr-based metal organic framework PCN-777 with or without modification with polymers like polyethyleneimine (PEI) and polystyrene (PS). The polymers were applied in this study in order to reduce the pore size of PCN-777 (P777) and to introduce basic sites when PEI was used. PCN-777 s loaded with both the PEI and PS were effective in CO2 adsorption because of reduced pore size; and PEI@PCN-777 s were highly effective in CO2 capture owing to basic sites on PEI. For example, the best adsorbent (among the studied PCN-777-based adsorbents), PEI(20%)@P777, showed around 2.3 and 5.7 times of adsorption capacity (at 0.15 atm) and selectivity (CO2/N2), respectively, as much as those of the pristine P777. Moreover, this MOF is recyclable and has the recommended heat of adsorption when adsorbed CO2 is not much. Therefore, it might be suggested that mesoporous MOFs, not suitable for CO2 capture under low pressure (because of too big pore), can be modified facilely for effective CO2 adsorption (especially under low pressure of 1 atm or less) by loading polymers with basicity onto the mesoporous MOFs.