High-performance membrane with angstrom-scale manipulation of gas transport channels via polymeric decorated MOF cavities

Abstract

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.