Eco-friendly porous composite of octaphenyl polyhedral oligomeric silsesquioxane and HKUST-1 with hydrophobic-oleophilic properties towards sorption of oils and organic solvents.

The degradation of water bodies caused by organic pollutants from industrial wastewater discharge has made it necessary to develop new functional materials like hydrophobic-oleophilic materials that can efficiently remediate water. It is factual that many of the synthetic methods for creating hydrophobic-oleophilic materials involve the use of toxic or harmful reactants, such as fluorine or sulfur compounds. However, these methods often have significant drawbacks, including being hazardous to the environment, expensive, and complex to utilize. Therefore, there is an urgent need to develop a hydrophobic/oleophilic material that is non-toxic and eco-friendly in order to overcome the existing drawbacks. In this regard, we have proposed a modest and eco-friendly approach for constructing a hydrophobic-oleophilic Ph-POSS@HKUST-1 composite material by solution-assisted self-assembly for the conversion of hydrophilic HKUST-1 into hydrophobic HKUST-1 for separation applications. The incorporation of fluorine-free, low surface energy and hydrophobic POSS into HKUST-1 increased the hydrophobicity and oleophilicity of the system. The synthesized Ph-POSS@HKUST-1 composite material has been thoroughly characterized through FT-IR, PXRD, HR-SEM, BET, and thermogravimetric analysis. It has been observed that the material exhibits a contact angle of 137 ± 4° and shows high selectivity and absorption capacity towards organic solvents and oils from water mixtures. Concurrently, the Ph-POSS@HKUST-1@PDA@sponge has been effectively utilized for the separation of solvents and oils and it has shown more than 95% separation efficiency for up to 15 cycles. It is interesting to note that Ph-POSS@HKUST-1 and the Ph-POSS@HKUST-1@PDA@sponge have outstanding stability in abrasive chemical environments which is due to the presence of a mechanically and chemically stable inorganic-organic hybrid POSS nanocage. In addition, ab initio and DFT calculations elicit that the Ph-POSS@HKUST-1 composite is stabilized through π⋯π stacking instead of the C-H⋯π mode of interaction at the HKUST-1⋯Ph-POSS interface. Further electron density features confirm the interfacial interaction at the interface. Our latest research has led us to propose an eco-friendly and non-toxic hybrid composite material for efficiently tackling the issue of organic solvent and oil pollution in water mixtures.