A sub-2nm two-dimensional polymer membrane with dense functionalized nanopores for high power density osmotic power generation

Osmotic power, electricity generated from salinity gradient, can potentially provide terawatt-hours of electricity annually around the globe. A semipermeable membrane with both high permselectivity and ionic conductance is at the basis of osmotic power generation. Here, we synthesized an ultrathin nanoporous membrane made from a two-dimensional polymer (2DP), which delivered a record high osmotic power generation density (~2000W/m²) exceeding the theoretical limit of traditional charge-based porous membranes. Our 2DP membrane was designed at the molecular level and synthesized using a novel interfacial method. The resulting membrane is less than 2nm thick and has dense sub-2nm pores decorated with phenolic hydroxyl groups. Molecular dynamics simulations suggested that the hydrogen bonding between phenolic hydroxyl groups and charged ions is responsible for the high permselectivity of the ultrathin nanoporous membrane. This work successfully utilized short-range interaction for osmotic power generation for the first time, introducing a new approach to designing high-performance osmotic power generation membranes.