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.