Engineered Heterogenous Subnanochannel Membranes with a Tri‐Continuous Pore Structure of Large Geometry Gradient for Massively Enhanced Osmotic Power Conversion from Organic Solutions

Abstract Heterogenous nanofluidic membranes with bi‐layer structures and ionic diode effect are shown great potential in efficiently harvesting the energy existing in a salinity gradient (or called the osmotic power conversion). However, exploitation of a heterogenous membrane with superior ion selectivity, excellent conductance, and strong ionic diode characteristics has remained a great challenge. Here, a novel heterogenous subnanochannel membrane with a tri‐continuous pore structure of a large geometry gradient ranging from sub‐nanoscale to nanoscale to sub‐microscale, which is composed of a thin and crack‐free layer of zeolitic imidazolate framework‐8 (ZIF‐8)/polystyrene sulfonate (PSS) membranes and an aligned branch‐type alumina nanochannel membrane (B ANM ) is reported. It is demonstrated that such a tri‐continuous pore structure can endow the exploited membrane, ZIF‐8/PSS@B ANM , with enhanced ion selectivity, strong ion current rectification, and ultrafast ion transport properties, in organic electrolyte solutions. Thus, an amazingly high power of ≈50.5 W m −2 is produced by mixing a 2 m LiCl‐methanol and pure methanol solutions, which is over 45‐fold higher than the existing membranes. Realizing high ion selectivity and amplified directional ion transport at sub‐nanoconfined spaces in organic solvents paves the new way to develop ion‐channel‐mimetic membranes toward efficient ion separation and high‐performance energy harvesters for battery applications.