电聚合新型聚间苯二胺薄膜及 H₂/CO₂ 分离性能研究

Membrane-based gas separations have tremendous potential for hydrogen purification due to high energy efficiency and easy operation, and the separation performance is significantly influenced by membrane materials. Owing to the low cost and processability, polymer membranes have been widely commercialized among these membranes. While, the trade-off between permeability and selectivity is insurmountable for dense polymer membranes. Therefore, introducing rigid porosity into polymer membranes is an urgent issue that needs to be solved. In our study, several aniline-based derivatives with multiple electrochemical active sites (1,3,5-triaminobenzene, o-phenylenediamine and m-phenylenediamine) were rationally designed and electropolymerized to yield novel conjugated microporous networks. Cyclic voltammetry technology was used for electropolymerization, and Ag/Ag⁺ electrode was selected as the reference electrode, with indium tin oxide (ITO) conductive glass and Ti sheet as the working electrode and counter electrode respectively. Finally, a homogenous and free-standing poly-m-phenylenediamine (PMPD) membrane was obtained after 40-circles electropolymerization. The polymerization reaction was confirmed by Fourier transform infrared spectroscopy (FTIR), solid-state ¹³C nuclear magnetic resonance spectra (¹³C NMR) and elemental analysis (EA). The morphology, thermal stability and porosity of PMPD were measured by scanning electron microscopy (SEM), thermogravimetric analysis (TG), and N₂-77 K sorption isotherm. The gas separation ability and mechanical performance of PMPD membrane were studied. The H₂/CO₂ separation selectivity reaches 30 with 1350 Barrer of H₂ permeability, which can exceed the Robeson upper bound. Furthermore, the thermal and 7 d long-term stability tests demonstrate their potential for industrial applications. The resulted H₂ diffusivity (120×10^–7 cm²•s^–1) of PMPD membrane was superior to CO₂ (2.4×10^–7 cm²•s^–1), which indicated that the diffusivity of H₂ playing a dominant role in separation process. Molecular dynamics simulations were subsequently carried out to mimic the adsorption and diffusion behaviors of H₂ and CO₂ in PMPD respectively. The results also demonstrated that H₂ exhibited more outstanding diffusivity than CO₂. This simple, scalable, and cost-effective electropolymerization strategy holds promise for the design of other conjugated microporous polymers for key energy-intensive gas separations.