Functionality Rotation-Mediated Solvent Separations in Nanochannel Membranes

Nanochannel membranes with 1-nm/sub-1-nm channels provide an energy-efficient and sustainable way of solvent separations for global process-based industries that operate on solvent mixtures. Channel modifications by binding selective functionalities are a widely adopted strategy to improve membrane selectivity, but it often compromises target solvents permeability, presenting a persistent and undesired trade-off dilemma. This is largely due to the relatively fixed position of the functionalities, whose steric hindrance unavoidably retards molecular transport at this scale. In contrast to previous designs, this project aims to develop a novel nanochannel membrane featuring rotatable functionalities. It takes advantage of functionality dynamics - rotations - to facilitate target solvent transport while blocking competing solvent, effectively overcoming the trade-off. The demonstration and verification of this idea are based on 3 steps, including (1) development of a prototype membranes using a 2D layered MXene assembly as backbone and ammonium ions (NH4+) as functionalities due to their intrinsic ultrafast rotation in solvents (e.g., water); (2) evaluation of the solvent separation performance (e.g., water-ethanol) of such membranes against MXene membranes functionalised by slow-rotating ions or no ion (pristine); (3) elucidation of the relation between functionality rotation and solvent transport/separation by coupling experimental results, key characterizations, and computational modelling.Project success will advance the state-of-the-art in practical, conceptual, and mechanistic aspects. A high-performance solvent separation membrane that breaks trade-off will be fabricated. A new nanochannel membrane design principle involving functionality dynamics will be established. Most importantly, a functionality rotation-mediated transport mechanism will be proposed as a new perspective to understand 1-nm/sub-1-nm mass transport in future membranes.