Superfast water transport mixed matrix membranes with asymmetrical micro-nanostructures reinforced by metal-organic...

Metal-organic framework (MOF) based nanofiltration (NF) membrane have emerged as the promising option in the field of efficient water purification. However, challenges associated with limited water transport ability of MOF-based NF membranes with conventional structures over separation process hinder the widespread application. This work, we proposed a nano-confined interfacial polymerization to prepare ultrahigh-flux supported MOF mixed matrix membranes (ZIF/PA membranes) with asymmetrical micro-nanostructures composed of two-dimensional zeolitic imidazolate framework (ZIF-L) and polyamide (PA) under suction force. In the membrane structure, the microscale asymmetric orientation distribution of ZIF-L nanosheets result in the most utilization of MOFs to forming the more regular and shorter diffusion paths; the nanoscale asymmetric hydrophilic interfacial channels between the PA and ZIF-L interfaces enhance the nanofluid transport of water molecules. Thus, the ZIF/PA membranes not only possess high rejection rate for versatile dye molecules (e.g., 99.99 % for Congo red, 99.84 % for Methyl green, 99.99 % for Methylene blue, 99.95 % for Methyl orange, 98.99 % for Reactive black 5, and 99.97 % for Reactive blue 194), but also the corresponding water permeance exceed the most membrane materials reported so far. And the prepared membrane also shows good performance in the real printing and dyeing wastewater treatment, further manifesting advantages for practical applications. Both experimental observations and molecular dynamics (MD) simulations substantiate that the water is transported through ultra-fast nanofluidic flow as a result of asymmetric and continuous interfacial nanochannels.