Facile Exfoliation of Silk Nanofibrils Enabled by Hydrogen Bond Network Reconfiguration in Deep Eutectic Solvent/Water Systems

Silk nanofibers (SNFs) with distinctive physicochemical properties are promising nanoscale building blocks of porous materials, yet high-yield exfoliation using green solvents remains challenging. Herein, hydrogen-bonding small molecules (water, methanol, and ethanol) were introduced into deep eutectic solvents (DESs) to reconfigure hydrogen-bond networks and promote exfoliation. Among them, DES/water mixtures proved most effective: adding 30 wt % water reduced average SNF diameter from 239 ± 184 nm to 109 ± 27 nm and delivered a yield of 98.3% within 24 h. The improvement is attributed to hydrogen-bond reorganization, decreased viscosity, and enhanced proton transfer. The resulting SNFs preserved silk's hierarchical structures and were assembled into flexible membranes with a tensile strength of 34 MPa. These porous membranes effectively removed microplastics, with rejection rates above 91% through combined size exclusion and adsorption. This work demonstrates DES/water mixtures as sustainable solvent systems for scalable SNF production and the fabrication of high-performance membranes for water purification.