ROMP for Metal-Organic Frameworks: An Efficient Technique toward Robust and High-Separation Performance Membranes

Mixed-matrix membranes (MMMs) with excellent mechanical and separation performance are usually challenging to be fabricated due to the significant incompatibility between nanofillers and the polymer matrix. This work provides a facile technique to construct MMMs through covalently attaching metal-organic frameworks (MOFs) within the polymer matrix via ring-opening metathesis polymerization. Norbornene-modified UiO-66-NH2 was successfully copolymerized into polynorbornene matrix in less than 10 min. Owing to strong covalent interaction among MOFs and polymers, exceptional toughening effects for MMMs through cavitation were observed. For MMMs with 20 wt % MOF loading, 520 times improvement in mechanical toughness was realized in comparison with neat polymers (52 vs 0.1 MJ/m3), far exceeding most of the previous MMMs. Such MMMs exhibited excellent gas separation performance for H2/CO2 and H2/N2 with high H2 permeability at 91-230 barrers and H2/N2 and H2/CO2 selectivity at >1000 and 6-7, respectively, surpassing the 2008 Robeson Upper Bound. As a proof for the scalable preparation of MMMs, a large and thin MMM (dimension: 98 × 165 cm; thickness: 3-5 μm) was also prepared in the factory for gas separation.