New
membrane materials with excellent water permeability and high
ion rejection are needed. Metal–organic frameworks (MOFs) are
promising candidates by virtue of their diversity in chemistry and
topology. In this work, continuous aluminum MOF-303 membranes were
prepared on α-Al2O3 substrates via an in situ hydrothermal synthesis method.
The membranes exhibit satisfying rejection of divalent ions (e.g.,
93.5% for MgCl2 and 96.0% for Na2SO4) on the basis of a size-sieving and electrostatic-repulsion mechanism
and unprecedented permeability (3.0 L·m–2·h–1·bar–1·μm). The
water permeability outperforms typical zirconium MOF, zeolite, and
commercial polymeric reverse osmosis and nanofiltration membranes.
Additionally, the membrane material exhibits good stability and low
production costs. These merits recommend MOF-303 as a next-generation
membrane material for water softening.
The computational simulation of porous graphene oxide (PGO) indicated that it has great potential for the preparation of gas separation membranes. However, scaling up the manufacture of multilayer, defect-free porous graphene oxide membrane with consistently sized nanopores is extremely challenging. Here, we prepared layer-by-layer CO 2 -philic Pebax @ 1657 membranes that were functionalized by o-hydroxyazo-hierarchical porous organic polymers (o-POPs) and PGO. The d-spacing of pristine PGO could be finely regulated through CO 2 -philic o-POPs to facilitate the permeability of CO 2 . In addition, the o-POPs exhibit "N 2 -phobic, CO 2 -philic" properties with the phenolic hydroxyl and the azo group. The best of the POP-PGO membrane exhibits that the CO 2 permeability and ideal selectivity of CO 2 /N 2 are 232.7 Barrer and 80.7, respectively, and it has surpassed the Robeson's upper bound (2008).
The synthetic membranes universally exhibit a pernicious trade-off effect, on which there exists an upper bound between permeability and selectivity. Tremendous efforts are made to design crumpled membranes to further...
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