Design And Synthesis Of Two-dimensional Porous Carbon Materials And The Mixed Matrix Membranes

With the rapid development of society,the greenhouse effect is exacerbated by the increasing emissions of greenhouse gases such as CO₂ due to the consumption of large amounts of fossil fuels.Therefore,separating CO₂ from industrial waste gases and treating it properly is the best way to mitigate the greenhouse effect and meet carbon emission targets.Mixed matrix membranes have become a research hotspot for CO₂ separation due to their promise to combine the advantages of organic and inorganic membranes,and the 2D materials as membrane fillers has received widespread attention due to their better gas separation performance.Conventional2D fillers have large gas transfer resistance in membranes due to their interfacial barriers.New2D porous carbon materials can be used as novel fillers for the fabrication of MMMs,which have a good prospect for improving the performance of CO₂ separation membranes.Firstly,in this work,MCNs precursors were synthesized by using stearic acid and F127 as"removable templates"and phenolic resin,and MCNs were finally obtained by a two-step carbonization activation method.The thickness is about 130 nm,the aperture is about 0.58 nm and,the S_BET was 775.72 m²/g.The MCNs/Pebax MMMs were then blended with Pebax-1657 to prepare the MCNs/Pebax MMMs,and it was confirmed by various characterisations that the MCNs microporous structure provided a low resistance CO₂ diffusion channel within the membrane,significantly increasing the CO₂ permeability.At the same time,the effective stacking of MCNs within the membrane formed a highly selective gas transport channel,improving the CO₂/N₂ selectivity.The MMMs containing 0.5 wt.%MCNs showed the best separation performance.In pure gas experiments,the CO₂ permeability and CO₂/N₂ selectivity were 123Barrer and 76 respectively,showing a significant increase of 53.0%and 28.8%compared to pristine Pebax membranes,exceeding the Robeson upper bounds in 2008.Finally,in order to improve the interfacial compatibility between MCNs and polymers and increase the membrane selectivity for CO₂ reaction,Mf MCNs were successfully synthesized by complex functionalization of MCNs using two different functionalized carriers,PEI and APTES.The synthesized Mf MCNs retained the original morphology of MCNs,with a pore size of 0.53-0.55 nm and a specific surface area of 701.04 m²/g The Mf MCNs were blended with Pebax-1657 to prepare the Mf MCNs/Pebax MMMs,and the SEM characterization showed that the dispersion and compatibility of Mf MCNs in the membrane were greatly improved.Pebax MMMs CO₂ permeability was 321.8 Barrer,an 82.2%improvement over the pristine Pebax membrane,and the CO₂/N₂ selectivity was 88.5,an improvement of 49.1%over the pristine Pebax membrane.This demonstrates that the Mf MCNs obtained by composite functionalization can significantly improve the gas separation performance of MMMs.