Precise Cation Recognition in Two-Dimensional Nanofluidic Channels of Clay Membranes Imparted from Intrinsic Selectivity of Clays

Abstract

Various kinds of clays occur naturally and are accompanied by particular cations in their interlayer domains. Here we report the reassembled membranes with nanofluidic channel arrays by using the natural clays montmorillonite, mica, and vermiculite, which were imparted with the natural selectivity for realizing precise recognition and directional regulation of the naturally occurring interlayer cations. A typical surface-governed ionic transport behavior was observed in the clay nanofluidic channels. Through asymmetric structural modification, cationic current rectification was realized in montmorillonite channels that performed as a nanofluidic diode. Interestingly, in the mica nanofluidic channel, the K+ that was naturally occurring in the interlayer domain of mica showed a reciprocating motion and resulted in a periodically fluctuating current. Electrodialysis demonstrated that such a fluctuating current reflects a directional selectivity for K+, achieving at least a 6000 times permeation rate difference with Li+ ions. The specific selectivity for Li+/Mg2+ on vermiculite reached up to 856 times with similar cations by the current technique. As-obtained clay membranes possess application prospects in energy conversion, brine resource development, etc. Such a strategy can achieve the designed selectivity through systematic screening of the building blocks, thus imparting them with the inherent characteristics of natural clays, which provides an alternative solution to the present manufacture of selective membranes.

Repulsive Osmotic Delamination: 1D Dissolution of 2D Materials

“…The surface characteristics of the channel mainly govern the transport properties. [ 100 ] Properties like charge, charge density, channel size, and individual interactions between the nanosheets and the transported ions come into play. The surface charge of the channels will effectively repel the co‐ions, while allowing only the counter ions to move though the slits.…”

“…water electrolysis, and battery materials. For instance, films of 2D materials can act as H + /OH − conductors in the case of fuel cells, [95a,98] or aid the ionic filtration [100] and recovery of valuable ions.…”

MXenes vs. clays: emerging and traditional 2D layered nanoarchitectonics

“…• Membranes for ion-recognition and oxygen sensors 91 • Membranes for ion-exchange processes 102 • Corrosion protection…”

Extreme Ion‐Transport Inorganic 2D Membranes for Nanofluidic Applications

“…[17,93] Zhang et al investigated the effect of interlayer cations on ionic selectivity. [138] They suggested that the interlayer cations make membranes highly selective for other types of cations (surface regulation effect). This emerges at a low electrolyte concentration (below 10 −3 mol L −1 of a chloride solution), where EDL of the clay nanosheets begin to play a predominant role in the cationtransport behavior inside the nanofluidic channel.…”