Wood Ion Pumps Enabled by Light-Responsive MoS2-Decorated Nanocellulosic Channels

Light-driven active ion transport discovered in nanomaterials (e.g., graphene, metal-organic framework, and MXene) implicates crucial applications in membrane-based technology and energy conversion systems. However, it remains a challenge to achieve bulk assembly. Herein, we employ the scalable wood as a framework for in situ growth of MoS₂ nanosheets to facilitate light-responsive ion transport. Owing to the aligned and negatively charged wood nanochannels, the MoS₂-decorated wood exhibits an excellent nanofluidic conductivity of 8.3 × 10^-5 S cm^-1 in 1 × 10^-6 M KCl. Asymmetric light illumination creates the separation of electrons and holes in MoS₂ nanosheets, enabling ions to move uphill against a wide range of concentration gradients. As a result, the MoS₂-decorated wood can pump ions uphill against a 20-fold concentration gradient at a light intensity of 300 mW cm^-2. When the illumination is applied to the opposite side, the osmotic current along the 20-fold concentration gradient can be enhanced to 75.1 nA, and the corresponding osmotic energy conversion power density increases to more than 12.6 times that of the nonilluminated state. Based on the light-responsive behaviors, we are extending the use of MoS₂-decorated wood as the ionic elements for nanofluidic circuits, such as ion switches, ion diodes, and ion transistors. This work provides a facile and scalable strategy for fabricating light-controlled nanofluidic devices from biomass materials.