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Significance Statement
The use of 3-dimensional porous oleophilic and hydrophobic materials with high adsorption capacity, low density and high oil-water selectivity are appearing to be good candidates for expelling oil contaminants from waste water from oil industries and oil spills. Organic (polyester, carbon-based and polyvinyl benzene) and inorganic hydrophobic materials such as metal oxide-metal based membranes, composites and sponges have been widely investigated for this application.
However, a number of challenges relating to reusability, gradual hydrolysis in water, multistep synthesis as well as poor oil-solvent pick up, come up. Hybrid organic-inorganic porous materials including metal-organic frameworks are helpful as high efficiency porous solids for gas separation and sensors owing to their unique structural order, and functional pores with superior chemical and thermal stabilities.
However, controlling porous metal—organic frameworks’ functionality and their moisture sensitive properties remains a problem. Developing stable hydrophobic materials through manipulating the frameworks’ chemical composition with respect to the applied organic likers in a bid to achieve strong metal—ligand bonds in moisture would be a solution to this.
In a recent paper published in Advanced Materials Kolleboyina Jayaramulu and colleagues developed an elementary procedure for synthesis of hierarchical composites which were based on metal-organic porous gels. Their main aim was to achieve the quick uptake of oils as well as high stabilities in a number of organic solvents.
Fluorinated graphene oxide was hybridized with aluminum based metal organic gel which contained aluminum cations, and benzene-tricarboxylate. The authors fabricated the aluminum based metal organic gel by mixing benzene tricarboxylic acid with aluminum nitrate. However, the gelation process depended on metal-organic liker coordination and the formation of hierarchical porous metal-organic gels via coordination perturbed self-aggregation of the metal-organic framework nanoparticles to produce the metal-organic gels.
The coordination between the aluminum ion clusters and benzene tricarboxylic yielded octahedral coordinated aluminum cations with carboxylate atoms. This was reference to the strong coordination bond relative to the aluminum cations solvation reactions. For this reason, the metal ions as well as ligands yielded the metal-organic framework like structure that aggregated to forming amorphous polymer.
The as-prepared hybrid fluorinated graphene oxide and metal-organic gel showed a 3-dimensional fibrillary micro network in which the fluorinated graphene oxide appeared to be the structure directing agent.
The authors applied scanning electron microscopy to analyze the morphological evolution of the prepared composite which appeared as a bundle of fiber networks. Through elemental mapping, they were able to conform the anticipated aluminum, carbon, fluorine and oxygen elements distribution. The morphology of the prepared composite was different from that of the metal-organic gel. Moreover, pore size distribution analysis indicated hierarchical pores in the range of 2-70 nm. This was pivotal to substantiate the concept that the self-assembly of the metal organic gel was influenced by the introduction of the fluorinated graphene oxide Here, the metal-organic framework nanoparticles were selectively chelated with oxygen functionalities of fluorinated graphene oxide which, in addition, provides pendant low surface energy C-F groups.
When the authors screened the hydrophobic-oleophilic composite for adsorption of hydrophobic organic solvents as well as oils, toluene, heptane, petroleum and others were chosen. The adsorption capacity of the composite was found to be 200-500%. The composite exhibited excellent hydrophobicity and oleophilicity (advancing water contact angle of 125° and oil contact angle of 0°) due to the hydrophobic C-F groups and high surface roughness. The larger macropores of the composite allowed faster oil uptake compared to reported metal-organic framework materials. Above all, the fibrous material exhibited superior reusability, and chemical inertness.
Reference
Kolleboyina Jayaramulu1,2, Florian Geyer3, Martin Petr4, Radek Zboril4, Doris Vollmer3, and Roland A. Fischer2. Shape Controlled Hierarchical Porous Hydrophobic/Oleophilic Metal-Organic Nanofibrous Gel Composites for Oil Adsorption. Advanced Materials 2017, 29, 1605307.
[expand title=”Show Affiliations”]- Inorganic Chemistry II, Ruhr-University Bochum, 44870, Bochum, Germany
- Chair of Inorganic and Metal-Organic Chemistry, Department of Chemistry and Catalysis Research Centre, Technical University of Munich, Garching, 85787, Germany
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
- Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacky University, Šlechtitelu˚ 27, 783 71, Olomouc, Czech Republic
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