Boosting CO2 transport in mixed matrix membranes by chitosan-MOF networks

The chitosan (CS)-grafted UiO-66-NH2 (U6N) (CSGUN) was synthesized and incorporated into Pebax matrix to fabricate mixed matrix membranes (MMMs) for boosting CO2 transport. The excellent CO2 separation performance was exhibited for MMMs due to the following reasons: U6N with the suitable porosity and abundant CO2 transport carriers can provide a unique "expressway" for CO2 to boost CO2 transport through MMMs. The grafting CS in CSGUN can connect Pebax (regular roads) and U6N (expressway), acting as an "on-ramp" between them to enrich CO2 and guide CO2 through U6N in an orderly manner. Thus, the constructed "on-ramp" and "expressway" in MMMs can improve CO2 separation performance. Furthermore, the CS-MOF networks were formed in MMMs through using CS molecular chains to connect U6N for enhancing CO2 separation performance of MMMs. Therefore, Pebax/CSGUN MMMs exhibited the excellent CO2 separation performance with the CO2 permeability of 558 ± 7 Barrer and the CO2/CH4 selectivity of 37.5 ± 0.7. The study indicated that MMMs with CS-MOF bridged networks had great potential for boosting CO2 transport by combining "expressways" and "on-ramp".