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

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 approximate to 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.

Automated summary

A novel heterogenous subnanochannel membrane with a tri-continuous pore structure has been reported, which exhibits enhanced ion selectivity, strong ion current rectification, and ultrafast ion transport properties in organic electrolyte solutions. By mixing solutions of different salinity, a high power output can be achieved, paving the way for efficient ion separation and high-performance energy harvesters.