In Situ Synthesis of TpPa COFs in Mixed Matrix Membranes for Enhanced CO2 Separation

Abstract

Covalent organic frameworks (COFs) show exceptional promise for CO₂-selective mixed matrix membranes (MMMs) due to their tunable porosity and structural robustness. To mitigate COF aggregation in MMMs, we present an in situ growth strategy by directly integrating COF precursors into a polymer matrix. By optimizing reaction conditions, we achieve uniform dispersion and successful in situ formation of TpPa (derived from 1,3,5-triformylphloroglucinol and p-phenylenediamine) within the Pebax matrix. The optimized membrane exhibits a high CO₂ permeability of 313.4 Barrer (45.8% higher than pure Pebax) and CO₂/N₂ selectivity of 22.6, along with long-term stability. Positron annihilation lifetime spectroscopy further reveals how the integration of COFs modulates the membrane’s free-volume properties. This study not only addresses filler dispersion challenges but also provides a viable approach for fabricating high-performance, stable CO₂ separation membranes.