Novel membrane materials for H₂ separation are wanted. How to overcome the “trade-off” between membrane permeability and selectivity is a tough challenge. Here we report new random organic framework membranes with benzimidazole and imine linkages to form hierarchical channels. Both high H₂-selective and fast H₂ transport pathways are created. The preparation parameters are thoroughly studied and the membrane structures are well characterized by SEM, AFM, NMR, XPS, gas sorption, etc. Effect of feed conditions on membrane performance, such as composition, pressure and temperature, is investigated. The membrane performance transcends the upper bounds of H₂/CO₂, H₂/N₂ and H₂/CH₄ with excellent stability.

Gas separation performance of mixed matrix membrane heavily depends on the pore structure of the nanofillers. Metal-organic frameworks (MOFs) are promising platform materials for constructing molecular-selective pores for specific applications. In this work, deliberately-selected polymers with CO₂ affinity (PVAm, Pebax and PEI) are employed as pore regulators to manipulate the pore chemistry and size of MOF UiO-66 nanoparticles and consequently control gas transport rate of CO₂ and N₂ molecules. The branched polymer (polyethyleneimine (PEI)) grafted UiO-66, denoted as UKI, is beneficial to enhancing the membrane selectivity. The UKI doped Pebax/mPSf membranes exhibit CO₂/N₂ selectivity up to 278, 6.5 times of the bare Pebax/mPSf membranes. Meanwhile, the CO₂ permeance is boosted from around 690 to 1120 GPU (1 GPU = 10⁻⁶ cm³ (STP)·cm⁻²·s⁻¹·cmHg⁻¹ = 3.35 × 10⁻¹⁰ mol m⁻² s⁻¹·Pa⁻¹). The block copolymer (poly(ether block amide) (Pebax)) grafted UiO-66, denoted as UKX, is conducive to increasing the membrane permeance. The UKX doped Pebax/mPSf membranes exhibited CO₂ permeance up to 1683 GPU, 2.45 times of the bare Pebax/mPSf membranes. Meanwhile, CO₂/N₂ selectivity increased from around 42 to 146. Additionally, excellent pressure-resistant property and outstanding stability are observed under simulated flue gas.