Polymer / MOF composite membrane much! Proton can holding the \”nose\” beam transmission

Design and preparation of proton channel transmission efficiency for efficient material separation, biosensors, energy conversion, is essential to further developments in the field of nano fluidic devices and the like. In recent years, scientists bionic inspired aquaporin structure, development of a series of similar structure with an efficient water / proton channel, the maximum transmission efficiency of a single channel of up to 3.4 × 10-12cm-3 / s [Science 357, 792- 796 (2017)], aquaporin further than an order of magnitude. However, these internal channels biomimetic structure is homogeneous, and can not be transmitted in one direction as water / proton as aquaporin. To solve this problem, recently, Wang Huanting Fellow Monash University, Australia, Zhang Professor Huacheng team joint Science and Technology University of China Professor Wu Hengan team developed a nano – sub-nanometer size gradient asymmetrical hourglass structure PET / MOF composite proton channel, shows unidirectional transmission characteristics and high proton selective transmission. Wherein, the most excellent overall performance PET / MIL-121 channel maximum rectification ratio close to 500, the proton conductivity of up to 240 mScm ^-1 . Molecular modeling of binding found in the study, high transmission efficiency PET / MOF interior of the composite channel from the ordered \”water chain\” structure inside the intermolecular hydrogen bond and the MOF confinement effect combine to form, and will lead to different MOF different \”water chain\” configuration; such as MIL 121-type formed inside a pentagon MOF \”water chain\” structure, a three-dimensional network structure formed by the passage of the carboxylic acid groups in the MOF can be made quickly and efficiently by protons. Meanwhile, proton transport from the nanoscale channels to sub-nanometer level PET MOF energy barrier during the passage is small, thus imparting unidirectional transmission characteristics of the composite channel. Further, the special physical and chemical properties of the internal passage also makes the sub-nanometer MOF PET / MOF channel composite having a high proton selectivity – the difference between the different concentrations of HCl solution, H ⁺ / Cl [123 ] – selectivity> 20, and selectively pure PET nanochannel only about 5.6. The study, entitled \”Unidirectional and Selective Proton Transportin Artificial Heterostructured Nanochannels with Nano-to-Subnano Confined Water Clusters \”of papers published in the\” Advanced Materials \”.

[Photo A]

adopted the use of growth despread prepared PET / MOF composite asymmetric heterostructure proton channel, the process shown in Figure 1. first, using the ion track channels etching techniques for producing hourglass configuration on a PET film of 12 um, and then a hourglass side growth technique introduced by reverse diffusion MOF, to prepare asymmetric heterostructures proton channel. physicochemical properties of MOF to investigate the effect of the internal passage of the proton transfer, the introduction of three different MOF structures in the PET compared to the hourglass channel , respectively, MIL-121, MIL-53 and MIL-53-NH2.

FIG. 2. MIL-121, MIL-53 MIL-53-NH2 type formed inside and MOF \”water chain \”molecular structure simulation resultsthe authors found that MOF internal sub-nanometer channel structure having great influence on the transport of water and protons. simulation binding molecules, the authors found in MIL-121 channel size of 8.7Å, water ordered molecules tend to form a five-membered ring structure \”water chain\”, such \”water chain\” with a carboxyl group may be formed with channels facilitate proton transport channel a three-dimensional net-like .MIL-53 and MIL-53-NH2 internal passage dimensions are 8.5Å and 7.5Å, tend to form four-membered ring and five-membered ring structure hybrid \”water chain.\” according to theoretical calculations and statistics, the number of hydrogen bonds in the order of the channel structure is MIL-121> MIL-53 > MIL-53-NH2, since the hydrogen bonds may be formed between the MIL-53 and MIL-53-NH2, only water molecules, while previous studies indicated that the increased number of channels in favor hydrogen bonding protons transmission.

FIG. 3. in the external voltage conditions, PET, and various PET / MOF composite viaProton transport channel performance test resultsIn HCl solution concentration and the like inside the tank, since the PET / MOF composite channel having unidirectional transmission characteristics, so no induced current in the system external negative voltage. However, when the voltage generated by the external negative to positive, the induced currents of various PET / MOF composite channel increases while increasing the external voltage, indicating PET / MOF for the composite channel H + has a higher transmission performance choice; without MOF containing pure PET hourglass channel at each external voltage is no induced current occurs. Wherein the inner passage of the largest number of hydrogen bonds MIL-121 showed the best performance of the proton transport, the voltage at the external conditions of 2V, the maximum rectification ratio close to 500, the proton conductivity of up to 240

mScm – 1 . OF DFT calculation by unidirectional transmission characteristics found PET / MOF composite channel are transmitted in different directions due to difference of energy barrier. Since the passage of water molecules MOF ordered structure, and a large number of transmission channels exist three hydrogen bonds, proton transport speed is much faster than PET channel, so that when the proton transport channels PET MOF channel direction, from large energy barrier small, unimpeded by the proton; and the transmission in the opposite direction, the energy barrier, accumulates protons from small to large in PET passage, thus affecting subsequent transport protons.

FIG. 4. PET and the composite channel PETMIL-121 H + / Cl- selectivity resultsof the focus on the PET / MIL-121 solution having a concentration difference of pool selective composite channel of H + / Cl-\’s. The results show that with the increase of the concentration difference of the induced current PET / MIL-121 composite channel is gradually increased; bath solution 0.001M / 0.01M of nano – sub-nanometer PET / MIL-121 composite channel H + / Cl- selectivity of about 20.3, while the selectivity of pure PET nanoscale channels 5.6; the concentration of the solution tank inverted selectively remains substantially unchanged. However, after the solution was found in the study of other alkali metal cations introduced into the pool, PET / MIL-121 complex channel will be significant decline proton transfer efficiency, because inside the channel, the alkali metal cations and water molecules will is formed between the hydrated ions, brokenBad ordered \”water chain\” structure.

[summary]

PET / MOF composite asymmetric heterostructure having both proton channel and sub-nanometer size of nano-prepared, exhibit excellent selectivity characteristics of the proton and unidirectional transmission in high , low-cost energy conversion and separation areas showed great potential. Original link: https: //onlinelibrary.wiley.com/doi/10.1002/adma.202001777