Superhydrophobic Co-MOF-based sponge for efficient oil-water separation utilizing photothermal effect

Effectively addressing crude oil spills remains a global challenge due to its high viscosity and limited flow characteristics. In this study, we successfully prepared a modified sponge (PCP@MS) by embedding the photothermal material of Co-HHTP and coating the melamine sponge (MS) with low-surface-energy polydimethylsiloxane (PDMS). The PCP@MS exhibited outstanding hydrophobicity with WCA of 160.2° and high oil absorption capacity of 59-107g/g. The PCP@MS showed high separation efficiency of 99.2% for various oil-water mixtures, along with notable self-cleaning properties and mechanical stability. The internal micro-nano hierarchical structure on the sponge surface significantly enhanced light absorption, synergizing with the photo-thermal conversion properties of Co-HHTP, enabled PCP@MS to achieve a surface temperature of 109.2°C under 1.0 solar light within 300s. With the aid of solar radiation, PCP@MS is able to heat up quickly and successfully lowering the viscosity of the surrounding crude oil, resulting in an oil recovery rate of 8.76g/min. Density functional theory (DFT) calculation results revealed that Co-HHTP featured a zero-gap band structure, rendering advantageous electronic properties for full-wavelength light absorption. This in situ solar-heated absorbent design is poised to advance the practical application of viscous oil spill cleanup and recovery. Environmental Implication Efficient treatment of oily wastewater and recovery of crude oil remain global challenges. Herein, we have prepared a superhydrophobic sponge loaded with Co-HHTP. This PCP@MS exhibits excellent photothermal conversion effects, oil absorption capacity and oil-water separation performance. Additionally, it can absorb high viscosity crude oil under one simulated sunlight. This sponge provides a feasible solution for treating oily wastewater and crude oil spill accidents. The DFT calculation results indicate that Co-HHTP exhibits metallic property, which is beneficial for improving the photothermal effect. In the future, this field should also focus on selecting superior green photothermal materials to minimize environmental pollution.