Super-wetting Cu-MOF-based foam for efficient oil/water separation and photothermal cleanup of crude oil

• Cu-HHTP@Cu exhibited excellent separation efficiency (>99.4 %) and flux (>92.1 kL∙m −2 ∙h −1 ). • Cu-HHTP@Cu effectively removed dyes over 90%. • PDMS@Cu-HHTP@Cu showed high separation efficiency (>99.8 %) and flux (>90.3 kL∙m −2 ∙h −1 ) for oil/water mixtures. • PDMS@Cu-HHTP@Cu achieved the crude oil absorption capacity of 11.9 g/g. • PDMS@Cu-HHTP@Cu demonstrated good stability and durability. Developing multifunctional and super-wetting separation materials is of great significance for treating complex oily wastewater in real environment. Herein, the superhydrophilic Cu-HHTP@Cu foam with hierarchical structure was fabricated by chemical oxidation and in situ growth strategies, which showed an outstanding separation efficiency (>99.4 %) and flux (>92.1 kL∙m −2 ∙h −1 ) for various oil/water mixtures. The electrostatic attraction, π − π interactions and hydrogen bonding between Cu-HHTP@Cu foam and dyes facilitate the adsorption process, with a removal efficiency > 94.7 %. To absorb high-viscosity crude oil, the Cu-HHTP@Cu foam was further modified with polydimethylsiloxane (PDMS) to finally obtain superhydrophobic PDMS@Cu-HHTP@Cu foam, which demonstrates high separation efficiency (>99.8 %) and flux (>90.3 kL∙m −2 ∙h −1 ). Both Cu-HHTP@Cu foam and PDMS@Cu-HHTP@Cu foam also showed stable durability after 20-cycle tests. More importantly, due to the introduction of Cu-HHTP, PDMS@Cu-HHTP@Cu foam presented excellent photothermal conversion behavior with the surface temperature reaching up to 72.0℃ under simulated sunlight, which remarkably facilitate the cleaning of crude oil. This work shows that modified Cu foam is a promising candidate for absorbing dyes and treating crude oil spills and is expected to provide a convenient method for oil/water separation.