Large-Area COF Membrane with Hourglass-Shaped Nanochannels for Enhanced Hydrogen Separation.

Efficient hydrogen purification from methanol steam reforming (MSR) faces challenges due to H2/CO2 kinetic diameter overlap and energy-intensive traditional methods. Here, we report a biomimetic hourglass-shaped covalent organic framework (COF) membrane via sequential spray coating of opposite charged COF nanosheets, mimicking aquaporin-like hierarchical channels. The sandwich structure (large-pore sulfonated COF outer layers, narrow-pore guanidinium COF middle layer) enables dual-functionality: outer TpBD-SO3H layers perform as the diffusion chamber (2.5 nm pores) and protective layer, whereas the middle TpTGCl layer (0.8 nm pores) traps CO2 via strong electrostatic interactions. The membrane achieves a H2 permeance of 2833 GPU and H2/CO2 selectivity of 21, surpassing the 2008 Robeson upper bound. Spray coating enables scalable fabrication of 5000 cm2 defect-free membranes on porous substrate with high mechanical stability and chemical resistance (mass loss < 0.3% in 150 °C methanol). Separation process simulations show a two-stage system boosts H2 purity to 96.7% with 94.3% recovery, outperforming pressure swing adsorption (PSA) in efficiency and energy consumption. This modular design offers a sustainable, scalable solution for industrial hydrogen purification and gas separation.