PI@TB blend membranes containing amorphous carbon for gas separation

Abstract

This study employs the same diamine monomer to synthesize polyimide (PI) and Tröger’s Base-based polymers of intrinsic microporosity (TB), which exhibit infinite miscibility due to like-dissolves-like phenomenon. The TB and PI exhibit significantly different thermal decomposition temperatures, enabling the partial carbonization of TB at a lower temperature while retaining the favorable mechanical properties of PI. Consequentially, This work propose a novel method to prepare blend membranes with a partial amorphous carbon structure. These membranes have excellent gas separation performance, similar to that of carbon membranes, while also retaining the machinability of traditional polymer membranes. The molecular structure of the material is characterized using 1H NMR and FTIR spectra, while the microscopic morphology is observed through scanning electron microscopy. Molecular dynamics simulations confirm the compatibility of both polymers and explain the improved properties. Gas transportation measurement confirms that PI@TB blend membranes demonstrate significant improvement in gas separation performance compared to original membranes. Specifically, enhancements in the gas separation performance of CO2/CH4, H2/CH4, and O2/N2 systems have been observed, with the CO2/CH4 pair demonstrating the most remarkable improvements, surpassing the 2019 Robeson upper limit. This design strategy can be applied to produce blend membranes containing amorphous carbon that exhibit great potential for high-performance separation processes in the future.