Cellulose-based, highly porous polyurethanes templated within non-aqueous high internal phase emulsions

Cellulose is one of the most abundant resources in nature. Cellulose-based porous monoliths have been fabricated by direct drying of oil-in-water high internal phase emulsions (HIPEs) stabilized using either cellulose derivatives or surface-modified cellulose. The resulting cellulose-based porous polymers, however, were usually fragile, reflecting the lack of crosslinking. Herein, we report a new strategy to fabricate cellulose-based porous materials (polyurethane polyHIPEs, PU polyHIPEs) templated within non-aqueous HIPEs through the covalent crosslinking between isocyanates and unmodified cellulose. The PU polyHIPEs exhibited interconnected macroporous structures and exhibited tunable wettability from hydrophilicity/oleophilicity to hydrophobicity/oleophilicity. The PU polyHIPEs were able to absorb a wide variety of oils, exhibiting relatively large capacities and high absorption rates. We further showed that the PU polyHIPEs were robust, and they did not fail under compressive stress even at strains of 70%. The robustness, large absorption capacities, rapid absorption, and hydrophobicity/oleophilicity make these cellulose-based PU polyHIPEs suitable for oil absorption and/or oil–water separation applications. Graphic abstract