20:T405,Covalent organic frameworks (COFs) have been proposed as alternative candidates for molecular sieving membranes due to their chemical stability. However, developing COF membranes with narrowed apertures close to the size of common gas molecules is a crucial task for selective gas separation. Herein, we demonstrate a new type of a two-dimensional layered-stacking COF-COF composite membrane in bilayer geometry synthesized on a porous support by successively regulating the growth of imine-based COF-LZU1 and azine-based ACOF-1 layers via a temperature-swing solvothermal approach. The resultant COF-LZU1-ACOF-1 bilayer membrane has much higher separation selectivity for H₂/CO₂, H₂/N₂, and H₂/CH₄ gas mixtures than the individual COF-LZU1 and ACOF-1 membranes due to the formation of interlaced pore networks, and the overall performance surpasses the Robeson upper bounds. The COF-LZU1-ACOF-1 bilayer membrane also shows high thermal and long-time stabilities.21:T43a,The construction of stable covalent organic frameworks (COFs) for various applications is highly desirable. Herein, we report the synthesis of a novel two-dimensional (2D) porphyrin-based sp² carbon-conjugated COF (Por-sp² c-COF), which adopts an eclipsed AA stacking structure with a Brunauer-Emmett-Teller surface area of 689 m² g^-1 . Owing to the C=C linkages, Por-sp² c-COF shows a high chemical stability under various conditions, even under harsh conditions such as 9 m HCl and 9 m NaOH solutions. Interestingly, Por-sp² c-COF can be used as a metal-free heterogeneous photocatalyst for the visible-light-induced aerobic oxidation of amines to imines. More importantly, in comparison to imine-linked Por-COF, the inherent structure of Por-sp² c-COF equips it with several advantages as a photocatalyst, including reusability and high photocatalytic performance. This clearly demonstrates that sp² carbon-linked 2D COFs can provide an interesting platform for heterogeneous photocatalysis.

	Year	Citations

References