Fluorine-Free and Durable Polydimethylsiloxane Microsphere-Coated Superhydrophobic Polyurethane Sponges with Tunable Photothermal Properties for Multifunctional Applications

The development of facile-to-fabricate, long-lasting, and fluorine-free superhydrophobic surfaces still poses a key challenge for their versatile applications. In this work, a fluorine-free, durable, and photothermal superhydrophobic polyurethane (PU) platform is constructed by integrating polydimethylsiloxane (PDMS) microspheres and adjustable photothermal absorbers into the PU matrix with the aid of PDMS as a binder. When lignin particles are selected as the photothermal components, the resulting lignin-based superhydrophobic PU sponge shows outstanding chemical stability, hydrothermal resistance, and mechanical durability across various test conditions along with strong adsorption capacities for a range of oils and organic solvents. By substitution of the photothermal absorbers, a candle soot-modified or MXene-modified superhydrophobic PU platform can be readily fabricated. With lignin particles, candle soots, and MXene as the photothermal absorbers, the superhydrophobic PU platform reaches maximum surface temperatures of 65.4 °C, 76.2 °C, and 82.0 °C under 1 sun irradiation, respectively. Benefiting from its excellent photothermal performance, the superhydrophobic PU platform achieves adsorption capacities of 36.5 g/g, 56.2 g/g, and 41.1 g/g for viscous crude oil and separation efficiencies of 98.5%, 98.9%, and 98.7% for crude oil and adsorbs a crude oil droplet (1 mL) within 60 s, 30 s, and 28 s under 1 sun irradiation, respectively. Additionally, the superhydrophobic PU platform can efficiently separate oils (such as crude oil and carbon tetrachloride) from both water-in-oil and oil-in-water emulsions and maintains an ice-free state at −18.6 °C under 0.6 sun irradiation. This study not only realizes the sustainable high-value utilization of low-cost byproducts but also provides a strategy for the rational design of fluorine-free and durable superhydrophobic platforms with tailorable photothermal properties for multiple practical applications.