Nanofluidic osmotic energy devices based on metal-organic frameworks

The use of reverse electrodialysis (RED) technology to collect clean and renewable salinity gradient energy is one of the effective ways to alleviate energy crisis and environmental problems. The ion exchange membranes (IEMs) used by traditional RED usually has problems such as low energy conversion efficiency and insufficient power density. Nanofluidic reverse electrodialysis (NRED), inspired by biological ion channels, seems to be able to solve these problems. Recently, metal-organic frameworks (MOFs) have become candidates for capturing osmotic energy due to excellent ion selective permeability, nanoscale pores and easy functionalization. In this paper, the recent progress of MOF-based nanofluidic devices for osmotic energy harvesting is reviewed. Then, we discuss the key factors that affect the osmotic energy harvesting in the nanochannel membranes, including surface charge, pore size, pore density, ion channel length and structure, and ionic diode behavior. Finally, the future development and challenges of MOF-based nanofluidic devices are prospected.