Using Maleimide-Induced Dual Cross-Linking Method to Fabricate High-Performance Mixed Matrix Membrane

Constructing mixed matrix membranes (MMMs) with excellent interfacial compatibility and superior anti-plasticization performance is still a challenge. Herein, we prepared a zeolitic imidazolate framework filler modified with maleimide (MI) cross-linking site (termed as ZIF-8-MI). Subsequently, this filler was blended into the polyimide (PI) matrix that also contains MI cross-linking site (termed as PMI), in order to construct a series of MMM. When the MMM was thermally treated at 350 °C, the ZIF-PMI interfacial cross-linking reaction took place, which was derived from the radical cycloaddition between ZIF-8-MI and PMI, thus promoting the interfacial compatibility between the fillers and the PMI matrix. Concurrently, the in situ cross-linking of the PMI matrix was also formed due to the similar MI-induced radical cycloaddition reaction. As a result, thanks to this dual cross-linking effect, the gas separation performance and the anti-plasticization ability of MMM were highly enhanced. The optimized MMM, termed as cPI-ZIF-8-SI-20%, achieved a CO₂ permeability of 1028 Barrer, while maintaining a CO₂/CH₄ selectivity of 39.2, and its overall separation performance surpassed the Robeson 2008 Upperbound. Moreover, its CO₂/CH₄ (50:50) mixed gas separation performance continuously exceeds the 2018 performance upper limit across the 2-25 bar pressure range. In addition, it also exhibited exceptional plasticization resistance with a critical plasticization pressure of 44 bar. We believe that this dual cross-linking method provides an important reference for the development of MMMs with good interfacial compatibility and decent antiplasticization performance.