Designing MOFs/CuCo-LDHs hybrid-based superhydrophobic sponge for speedy eliminating microplastics, dyes, and oils from high-salinity water

Abstract

It is urgent to develop effective materials to decontaminate wastewater owing to water scarcity in the whole world. In this study, we successfully fabricated a superhydrophobic and superoleophilic MOFs/LDHs based-functional sponge (OMCTS/ZIF-67/CuCo-LDHs@Sponge) with large specific surface area and high porosity for the first time through a two-step co-precipitation method and surface modification of polysiloxane. The polydopamine (PDA) molecules not only greatly improved the adhesion between coatings and substrate, but also enhanced growth of MOFs and LDHs structure. The in-situ growth of hexahedron ZIF-67 particles on multiple layered CuCo-LDHs sphere formed heterojunction, which significantly increased adsorption sites, specific area, and porosity and also solved the aggregation problem of powder MOFs. The CuCo-LDHs with large surface area was beneficial to ZIF-67 growth owing to same Co2+connection. The developed superhydrophobic sponge not only quickly and selectively absorbed various microplastics (MPs, as high as 500 mg/mL), dyes (C0 = 40 mg/L, removal rate of 99.6 %), and emulsified oils from high-salinity water with high capacity (e.g. 85 mg/g for PP-2000, 94 mg/g for PS-100, and 93 mg/g for PE-2000), but also exhibited outstanding synchronous decontamination capability for coexisting pollutants through multi-molecular synergistic mechanism and multiple adsorption forces (grasping force, strong capillarity, electrostatic interaction, hydrogen bonds, π-π interactions, p-π conjugation interaction. Van der Waals forces). The coated sponge showed superior mechanical durability, which still maintained separation ability above 98 % after repeated adsorption of MPs for 40 cycles. The adsorption mechanism was detailly investigated through theoretical simulation of adsorption energy. This coated sponge was destined to show broad and useful applications in water purification field.