Construction of superhydrophobic PDMS@MOF-199/wood sponge hybrid membrane for ultrahigh-flux gravitational oil/water separation

Wood-derived materials have been utilized to develop filtration membranes for sustainable oil/water separation. However, it remains a significant challenge to manufacture durable wood-based membranes with high efficiency and ultra-high flux by simple methods. Herein, we report a facile strategy to fabricate a novel superhydrophobic hybrid wood membrane (PDMS@MOF-199/WS) with ultrahigh-flux and excellent oil/water separation performance. Firstly, copper-based metal organic frameworks (MOF-199) were in situ grown on the TEMPO-oxidized wood sponge (TO-WS) substrate to construct a hierarchical micro-nano structure with internal inherent microchannels. Secondly, a super-wetting surface was formed through soaking in polydimethylsiloxane (PDMS) and heat treatment. Remarkably, the water contact angle (WCA) of PDMS@MOF-199/WS could reach 163° and the oil contact angle (OCA) was around 0°, which remained stable over a long period of ultrasonic treatment and tape peeling. More importantly, the as-prepared modified wood membrane can efficiently separate a wide range of immiscible oil/water mixtures, solely by tiny gravity, with ultra-high flux of 10,385 L m −2 h −1 (carbon tetrachloride/water) and separation efficiency of 99.6% (n-hexane). Furthermore, this novel membrane can also effectively separate surfactant-stabilized water-in-oil emulsions with an efficiency of as high as 97.8%. Meanwhile, the hybrid membrane displayed exceptional reusability, maintaining a high-flux of 8599.6 L m −2 h −1 and retaining WCA at 154.8° after 12 cycles. Our results demonstrate that the synergetic impact of MOF-199 and PDMS as a means of encoding on-surface wettability substantially improved the separation efficiency. This work opens a new avenue for the design of functional wood-derived filtration membranes for the ultrahigh flux oil–water separation.