Elucidating Ultrafast Molecular Permeation through Well‐Defined 2D Nanochannels of Lamellar Membranes

Abstract

Lamellar membranes with well‐defined 2D nanochannels show fast, selective permeation, but the underlying molecular transport mechanism is unexplored. Now, regular robust MXene Ti3C2Tx lamellar membranes are prepared, and the size and wettability of nanochannels are manipulated by chemically grafted hydrophilic (−NH2) or hydrophobic (−C6H5, −C12H25) groups. These nanochannels have a sharp difference in mass transfer behavior. Hydrophilic nanochannels, in which polar molecules form orderly aligned aggregates along channel walls, impart ultrahigh permeance (>3000 L m−2 h−1 bar−1), which is more than three times higher than that in hydrophobic nanochannels with disordered molecular configuration. In contrast, nonpolar molecules with disordered configuration in both hydrophilic and hydrophobic nanochannels have comparable permeance. Two phenomenological transport models correlate the permeance with the mass transport mechanism of molecules that display ordered and disordered configuration.

A transport channel-regulated MXene membrane via organic phosphonic acids for efficient water permeation

“…This was further studied by XRD. The pure MXene membrane displays the (002) peak located at 7.2°, 27 corresponding to a d-spacing of 1.22 nm (Fig. 2g), while 2P/MXene, 3P/MXene and PA/MXene membranes show enlarged nanochannels with sizes of 1.31, 1.35 and 1.65 nm, respectively.…”

MXene Materials for Designing Advanced Separation Membranes

“…We expect simulation studies to shed more light on the transport mechanisms of MXene-based membranes in the future. In fact, the very recent contributions of Shamsabadi et al [114] and Wu et al [18] on gas and liquid separations, respectively, validate this expectation. Using MD simulations, Shamsabadi et al revealed the crucial role of interfacial interactions between PA blocks of Pebax 1657 and Ti 3 C 2 T x for achieving high CO 2 permeability of resulting MMMs.…”

“…It is well-established that the flux of incompressible and Newtonian fluids passing through channels made up of 2DMs can be described well by Hagen-Poiseuille law, Equation 3. The utility of Hagen-Poiseuille law for MXene-based membranes have been shown by Wang et al [109] and Wu et al [18] for NLMs, and Wei et al [130] for TFNs. In accordance, the permeance values obtained in both cases were inversely proportionate to the viscosity of the organic solvents tested.…”

“…During or after the etching-aided delamination/exfoliation of MAX phases, it is possible to introduce a variety of functional groups to MXenes, which provides another level of tunability. [17,18] Hence, MXenes constitute a highly versatile superfamily of nanomaterials and bring an unprecedented level of materials design capability at the disposal of advanced membrane research.…”

Radiation‐Induced Self‐Assembly of Ti3C2Tx with Improved Electrochemical Performance for Supercapacitor

“…The formulas of MXene and MAX are M n+1 X n T x and M n+1 AX n , respectively, in which M refers to early transition metal, X refers to C and/or N, A refers to A-group element, T refers to surface-terminating functional groups, such as oxygen (O), hydroxyl (OH), or fluorine (F) that are attached to the surface M atoms after the etching procedure, and x refers to the number of termination groups. [8,9] Because of their unique properties, such as layered structure and large surface area, tunable surface properties and hydrophilia, and high electrical conductivity, MXene have already shown promising performance in many applications, including energy storage, [10][11][12] electromagnetic interference shielding, [13] functional filler for organic materials, [14] highly efficient transport and separation, [15] catalysis, [16] and so on.However, the inevitable restacking of MXene nanosheets due to the strong van der Waals interaction still limits the ion transport, [17] and reduces the specific surface area and active sites, which will result in significant loss of electrochemical performance. [18,19] Researchers have made efforts to overcome this problem.…”