Constructing a Nonfluorinated, Durable, and Photothermal Superhydrophobic Polyurethane Sponge by Utilizing a Dual-Layer Design of Acetylene Black and Lignin Microparticles for Multifunctional Applications

The fabrication of superhydrophobic sponges with multifunctionality is of great importance in various practical fields. Herein, a fluorine-free, durable, and photothermal superhydrophobic polyurethane (PU) sponge is obtained using a dual-layer design, consisting of acetylene black (AB) via the adhesion of epoxy resin and lignin microparticles (LMPs) via the adhesion of polydimethylsiloxane (PDMS). The introduction of AB and LMPs not only creates hierarchical surface roughness on the skeletons of the PU sponge but also acts as photothermal absorbers. The as-prepared superhydrophobic PU sponge possesses excellent chemical resistance, hydrothermal and photothermal stabilities, and mechanical durability. Due to surface superhydrophobicity and superoleophilicity, it exhibits high adsorption capacities up to 56.3 g/g for various oils and organic solvents, and shows high separation efficiencies up to 99.9%. Benefiting from an enhanced photothermal property caused by introducing AB and LMPs, the superhydrophobic PU sponge displays a maximum surface temperature of 75.8 °C under 1 sun irradiation. Consequently, it can rapidly adsorb a droplet of viscous crude oil (1 mL) within 70 s (1 sun), and achieve an ice-free property at -18.5 °C (0.5 sun). Furthermore, the superhydrophobic PU sponge can effectively separate water-in-oil (or oil-in-water) emulsions and adsorb five types of microplastics (PE, PP, PET, PS, and PVC) due to the rich functional surface groups. This work provides a dual-layer design for fabricating fluorine-free, durable, and photothermal superhydrophobic PU sponge, and opens a new avenue for preparing superhydrophobic sponges with multifunctionality for diverse practical applications.