Enhancement of H2 Separation Performance in Ring-Opened Tro?ger's Base Incorporating Modified MOFs

Energy-efficient hydrogen (H2) recovery technology is of great significance to developing H2-based economy and accomplishing global carbon-neutrality with minimized worldwide energy consumption. A ring-opened Tro''ger's base (TBOR) polymer membrane as a highly H2-selective membrane holds great promise for recovering H2 while partial microporosity loss induced by ring opening reaction deteriorates the H2 permeability across the pure membrane. Herein we introduce polydopamine-modified ZIF-8 (PDA-ZIF-8) nanoparticles into TBOR to develop a permeable membrane for selective H2 separation. The resultant mixed matrix membranes demonstrate the significantly improved H2 permeability, owing to the porous structure of ZIF-8, and efficiently exclude large molecules of CH4 and N2, giving rise to promising H2/CH4 and H2/N2 ideal selectivities. The PDA-ZIF-8 interacts with the secondary amines of TBOR via hydrogen bonds, creating good interfacial adhesion, thus preventing a sharp selectivity loss that occurred in most mixed matrix membranes upon increasing filler loadings. At a maximum ZIF-8 loading of 50 wt %, the pure H2 permeability is 457 Barrer, increasing to 4.2 times as compared with the undoped membrane, and the ideal H2/CH4 selectivity of 57 and ideal H2/N2 selectivity of 59 are achieved. The H2/CH4 separation properties remain unchanged upon increasing feed pressures, indicating the membrane's good stability when operated at realistic high pressures. The ring-opening functionalization of Tro''ger's base has proven to be very useful for fabricating selective mixed matrix membranes and can be extended for designing H2-selective hybrid membranes with other porous fillers.

Automated summary

Energy-efficient hydrogen recovery technology is crucial for the development of hydrogen-based economy and achieving global carbon-neutrality. In this study, polydopamine-modified ZIF-8 nanoparticles were introduced into a Tro''ger's base polymer membrane to develop a permeable membrane for selective H2 separation. The resulting mixed matrix membranes exhibited significantly improved H2 permeability and good stability.