The next generation of hydrogen separation membrane turned out!

Hydrogen (H2) as a clean energy more and more popular. Currently separation membrane main way to get H2, but not high permeability of commercially available film. In recent years, the microporous solid materials (such as zeolites and MOF) having a rigid network structure and pore structure perfectly made considerable progress, a thin film made of such a material having a high permeability, selectivity is good. Porous organic cage (POC) and the microporous polymer (PIM) while the processing solution may be performed, but the lack of structural stability. Conjugated microporous polymers (CMP) is a through the aryl – aryl bond covalently interconnected π-conjugated cross-linked network, high structural stability, but poor in workability, and a wide pore size distribution (10 ~ 30Å ), it is difficult for gas separation. CONCLUSIONS generation of hydrogen separation membrane with a rigid network structure need to ensure high gas permeability, pore structure requires perfect to ensure a good selectivity, but also can be prepared by solution method. In order to prepare a high structural rigidity, solution processable hydrogen separation membrane, and three other research institutions NUS Preparation of thermosetting-based microporous film (CMT) conjugated a hydrogen separation membrane generation this material has a perfect pore structure : pore size 0.4 nm, a specific surface area of ​​up to 840 m2 · g-1, the processing method of using a solution after a large size film, H2 of permeability up to 28280 barrer [ 123], H2 of the selective CO2, O2, N2, CH4, C3H6, and C3H8 were more than 630 . Further, the film permeability and selective attenuation CMT 700 h of continuous operation at 150 ° C for not occur, showing excellent stability, can work at 500 ℃ film. Synthesis and characterization of microporous thermoset conjugate

Figure 1. Synthesis and characterization of microporous co thermoset yoke. (A) The production of 3D schematic, 2D and 1D structure of CMT, making 3D patterned CMT when the substrate is patterned floor, making 2D CMT substrate is a silicon wafer, the production of 1D CMT substrate is a copper nanowires; (b) 3 -TBTBP thermogravimetric analysis; (c) DSC curve of 3-TBTBP; (d) patterning 3TEM image (f) a one-dimensional CMT nanotubes;; SEM image D CMT\’s; the AFM image about 5nm thick CMT film on (e) a silicon wafer analysis of membrane pore size (g) Ar adsorption distribution, and measured at 86 K CMT of the Ar adsorption isotherm; (H) based on the measurement of positron lifetime PALS CMT and free volume of distribution at 35,100 and 150 ℃; d, e and f are of dimensions 20μm, 3μm and 200 nm.In 3,6,12,15- researchers tetrabromo tetrabenzoporphyrin phenazine (3-TBTBP) as precursor, at 540 ℃ under an inert atmosphere, based on the debromination and CC cross-coupling reaction realized polymeric precursor, to give a material having a CMT 1D, 2D, and 3D structures on different substrates. 3-TBTBP sublimation will occur sequentially, and melt polymerization during heating. TGA analysis indicates that, in a nitrogen atmosphere, there are two stages of weight loss in a temperature range of 200 ~ 900 ° C: the first stage is from 450 ° C to start the sublimation; second stage from 520 ° C to start is the 3-TBTBP debromination. To further understand the process of heating the phase change, the researchers 3-TBTBP DSC analysis, it was found experience precursor is melted 509 ° C, 515 ° C after the exothermic peak of polymerization and debromination. Researchers patterned surface of the 3D structure of CMT were characterized by SEM and found that a material having a uniform and dense structure, no internal cavities. A silicon wafer uniformly polymerized CMT film thickness of about 5.0 nm, and may be adjusted by changing the ratio of the surface area of ​​the precursor and the template substrate. Analysis porosity CMT researchers annihilation lifetime spectroscopy (PALS) by Ar adsorption / desorption isotherms and positron. It found that adsorption characteristics exhibited CMT type 1 and the like, which is P / P0 absorption rate is less than 0.01, typical of microporous materials, a BET surface area and pore volume were 840 m2 · g-1 and 0.39 cm3 · g-1. Researchers non-local density functional theory to calculate the pore size distribution mainly in the CMT of 0.4 ~ 0.5 nm, results in good agreement with the PALS.

Total Synthesis and characterization of microporous film of the thermosetting conjugated

Table 2. Synthesis of FIG film CMTSign. Images and crystal mixture (a) 3-TBTBP precursor NaCl; (B) CMT coated NaCl in the image; (c) CMT / chloroform solution showed Tyndall effect; (D) CMT solution of a concentration of 0.05 mg · ml -1, solvent: (1) methylene chloride, (2) ethanol, (3) methanol, (4) hexane, (5) diethyl ether, (6) acetone, (7) dimethylformamide, (8) CMT film (e) was prepared by the diameter of the filter is about 47 mm;; dimethyl sulfoxide, (9) and tetrahydrofuran (10) a surface SEM image isopropanol (F) CMT films; (G) CMT film cross-section SEM images, f and g respectively 2μm scale and 10μm.To prepare a film CMT, researchers first 3-TBTBP NaCl and mixed, and then heated for polymerization, after cooling to room temperature, soaked in deionized water for 3 hours to remove NaCl, filtered, freeze-dried, CMT is obtained a film. The researchers found that CMT films prepared with high dispersion stability in common organic solvents, stored at room temperature for two weeks and no sign of precipitation occurred, and was also found in a chloroform solution of the Tyndall effect characteristic of a colloidal dispersion. Observed by SEM cross-sectional surface of the layered structure CMT, crack-free surface but slightly wrinkled.

Conjugate hydrogen separation performance of the microporous film of the thermosetting

The gas separation performance CMT film

3. FIG. (A) transmembrane pressure at 30 deg.] C and 1 bar through a single gas permeability CMT film 1 μm thick (He, H2, CO2, O2, N2, CH4, C3H6 and C3H8); (bd) H2 / CO2, Robeson FIG H2 / N2 and H2 / CH4, the pink lines represent the upper limit of 1991, the green line represents the upper limit of 2008, the black line represents the upper limit of 2015; (e) in the CMT model, of CO2 (left) and H2 (the right ) can enter a space, the red circles represent the right space compared to CO2, H2 additional accessible; (f) at a transmembrane pressure of 150 deg.] C and 1 bar by mole of 1 μm thick films of the like CMT H2 / CO2 mixed gas for long-term testing.RESEARCHInvestigators have studied gas separation properties of the film CMT. It found that the transmembrane pressure at 30 deg.] C and 1 bar various gas permeability is inversely proportional to its aerodynamic diameter, 1 m thick film of He and H2 CMT exhibit ultra-high permeability, respectively 24200 and 28280 barrer, and other relatively low gas permeability: CO2 (4480 barrer), O2 (2680 barrer), N2 (2500 barrer), CH4 (2590 barrer), C3H6 (2330 barrer), C3H8 (2260 barrer). Meanwhile, H2 selectivity for CO2, O2, N2, CH4, C3H6, and C3H8 were 6.3,10.6,11.3,10.9,12.1 and 12.5. Further, when the film thickness increases from 500 nm 13μm, permeability and selectivity is almost no change. When the temperature rises from 30 ° C to 150 ° C, H2 penetration increased by 40% to 40680 barrer, H2 / CO2 selectivity of 6.05, permeability and selectivity run 700 hours no change at 150 deg.] C, at a temperature of 500 deg.] C of the film can be run properly. Material for the next generation of hydrogen separation film needs to have a sufficiently high hydrogen permeability and selectivity. Researchers summarizes the H2 / CO2, H2 / N2 and H2 / CH4 Robeson FIG gas, the contrast of the CMT, the PIM latest ultra-permeable, microporous solids having a network structure (zeolite, the MOF, porous organic polymers, etc.) , 2D inorganic material (GO, MXenes) and other properties of the organic polymer film. CMT membrane permeability was found – all optional data 2008 is much higher than the upper limit of the gas is also higher than the upper limit of the recently proposed in 2015 H2 / N2 and H2 / CH4 gas, showing a super permeability to hydrogen. Researchers believe that a microporous structure between the inner layer and the free span is the reason CMT plane 2D structure CMT film high hydrogen permeability. In order to determine the mechanism of the CMT gas separation, researchers also molecular dynamics simulation, the film was found CMT accessible volume H2 19.58% of the membrane volume, CO2 is higher than 16.28%, indicating that CMT can accommodate more H2, H2 and the average transmembrane RoadDiameter of 710Å, is much lower than 3715Å CO2, H2 and therefore exhibit ultra-high permeability.

Summary Based on the characteristics conjugated microporous thermosetting material (CMT), and three other research institutions prepared NUS a next generation of hydrogen separation membrane, having good structural rigidity, solution processable. At 540. They deg.] C, in an inert gas atmosphere of 3-TBTBP precursor by debromination and CC cross-coupling reaction to achieve the synthesis of 1D, 2D and 3D structures of CMT, the pore size of the membrane prepared 0.4 nm, a specific surface area up to 840 m2 · g-1. At 30 deg.] C and a transmembrane pressure of 1 bar, 1 m thick film CMT H2 permeability staggering 28280 barrer, H2 selectivity for various gases were over 6.3, but not with the film thickness variation. When the separation temperature was raised from 30 deg.] C to 150 ℃, H2 permeability increased by 40%, up to 40680 barrer, H2 / CO2 selectivity of 6.05, the film can operate normally at this temperature for 700 hours, 500 deg.] C even under normal operation. Description link