Hydrophobicity-Adjustable MOF Constructs Superhydrophobic MOF-rGO Aerogel for Efficient Oil–Water Separation

Accurate hydrophobicity adjustment of single-phase material is quite challenging and meaningful for water treatment. Here, a strategy combining crystal morphology regulation and post-synthetic modification is reported based on a novel metal-organic framework (MOF, Eu-bdo-COOH, H₄bdo = 2,5-bis(3,5-dicarboxylphenyl)-1,3,4-oxadiazole). The hydrophobicity is regulated by crystal size and morphology regulation, and a rough microspherical MOF is successfully synthesized. Meanwhile, the obtained MOF microspheres exhibit high water, chemical, and thermal stability. The post-synthetic modification of alkyl chains achieves fine-tuning of hydrophobicity of MOF microspheres. The static water contact angles can controllably range from 43 to 142°, and the amylamine-modified MOF (AM) obtains the strongest hydrophobicity. In addition, a superhydrophobic aerogel is constructed with AM microspheres and reduced graphene oxide (rGO) for efficient oil-water separation. The AM-rGO aerogel (AM-rGA) exhibits fast and efficient absorption of various oily substances from water, and the adsorption capacity of dibromoethane reaches up to 14,728 wt %. This outstanding oil adsorption capacity can maintain even beyond 50 cycles by the support of the stable aerogel. The strategy of morphology regulation and post-synthetic modification provides a broad approach for the hydrophobic adjustment of numerous MOF materials.