Boosting Osmotic Energy Harvesting from Organic Solutions by Ultrathin Covalent Organic Framework Membranes

Extracting osmotic energy from waste organic solutions via reverse electrodialysis represents a promising approach to reuse such industrial wastes and helps to mitigate the ever-growing energy needs. Herein, a molecularly thin membrane of covalent organic frameworks is engineered via interfacial polymerization to investigate its ion transport behavior in organic solutions. Interestingly, a significant deviation from linearity between ion conductance and reciprocal viscosity is observed, attributed to the nanoscale confinement effect on intermolecular interactions. This finding suggests a potential strategy to modulate the influence of apprarent viscosity on transmembrane transport. The osmotic energy harvesting of the ultrathin membrane in organic systems was studied, achieving an unprecedented output power density of over 84.5 W m^-2 at a 1000-fold salinity gradient with a benign conversion efficiency and excellent stability. These findings provide a meaningful stepping stone for future studies seeking to fully leverage the potentials of organic systems in energy harvesting applications.