Constructing Electronic Domains by Donor–Acceptor Covalent Organic Frameworks in Mixed Matrix Membranes for Dual-Domain Recognition of CO ₂

In this study, 2,4,6-triformylphloroglucinol (TP) was selected as the electron donor and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline (TAPT) as the electron acceptor to synthesize the donor–acceptor covalent organic framework (TATP-COF) via the Schiff base condensation reaction. This material was then used as a nanofiller to embed into Pebax-based mixed matrix membranes (MMMs) to enhance the CO2/CH4 separation performance. TATP-COF constructs electron-rich and electron-deficient domains in MMMs. The results of grand canonical Monte Carlo simulations and density functional theory calculations indicate that the electron-rich and electron-deficient domains can achieve dual-domain recognition of CO2. Specifically, the electron-rich and electron-deficient domains interact with electron-deficient C and electron-rich O in CO2, respectively. Consequently, the dual-domain recognition mechanism endows Pebax/TATP-COF MMMs with an exceptional CO2 separation performance. At 3 wt % loading, the CO2 permeability surges by 153.06% (1130.14 Barrer) and the selectivity rises by 31.33% (28.20) compared to the pure Pebax membrane. Thus, the formation of electron-rich and electron-deficient domains in MMMs constructed by TATP-COF exhibits considerable promise and potential to enhance the CO2 separation performance.