Fabrication Biomimetic Enzyme/Pebax Mixed Matrix Membrane And Study CO₂ Facilitated Transport Mechanism

The rapid development of industrial society and the sharp increase in population have led to a large amount of CO₂emissions,causing a series of environmental and climatic problems,which seriously affect the living environment of human beings.Membrane separation technology is a fast-developing new separation technology with the advantages of high efficiency,green and energy saving.Therefore,membrane separation technology may be an effective way to solve the large amount of CO₂emissions.Carbonic anhydrase（CA）,as a“CO₂-philic”biological enzyme,can increase the water and rate of CO₂to approximately1.6×10⁶s^-1in the state of free,showing the potential for efficient capture of CO₂.Biological enzymes have the disadvantages of poor stability and difficult to recycle,while biomimetic enzymes have excellent chemical stability and interfacial compatibility.In order to solve the above problems,a composite material（Co-BBP@POP-1）,which the biomimetic enzyme（Co-BBP）loaded on the surface of porous organic polymer（POPs）,and biomimetic enzyme（CFA-1）were prepared in this work,and the MMMs with high-efficiency CO₂catalytic capacity.Then,the separation performance of MMMs for CO₂/N₂was studied,and the mechanism of the membrane to promote CO₂transfer was investigated.The main research contents are as follows:（1）POPs own“CO₂-philic”group（-azo）and“N₂-phobic”group（-OH）,which can improve the membrane’s CO₂/N₂separation ability.Meanwhile,the metal ions such as Co²⁺,Zn²⁺,Ni²⁺can chelate with the azo and phenolic hydroxyl groups of POPs and achieve the metal ions loading.This work makes full use of this characteristic of POP-1,loaded metal ion-based bionic enzymes onto the surface of POP-1,successfully.And Co-BBP@POP-1 with high-efficiency CO₂catalytic ability was synthesized.The synthesized Co-BBP@POP-1 was dispersed in a polyether block amide（Pebax-1657）matrix to prepare a series of MMMs containing different amounts of Co-BBP@POP-1nanosheets.The transfer of CO₂in the membrane is greatly promoted,due to the synergistic effect of POP-1 and Co-BBP.MMMs containing 5 wt%Co-BBP@POP-1 showed the higher CO₂permeability,which was9.5 times than the pure Pebax membrane.Its CO₂permeability is 886 Barrer,and the CO₂/N₂selectivity is 94.2（dry）,which surpassing the Robeson upper bound（2008）.Under mixed gas humidification,the CO₂permeability of the Co-BBP@POP-1 Pebax membrane was greatly increased to 1620 Barrer,and the CO₂/N₂selectivity remained at 102,it can be attributed to the increase in the catalytic activity of the biomimetic enzyme.In addition,the prepared Co-BBP@POP-1 Pebax MMMs has good mechanical properties and long-term operation stability.（2）CA is a zinc-containing biological enzyme,in which the Zn²⁺active center is the key to convert CO₂to carbonate.The new biomimetic enzyme CFA-1 has similar Zn²⁺active centers.Moreover,it has excellent repeatability,solvent stability and thermal stability than CA,showing a broad application prospect.The MMMs containing 3 wt%of CFA-1 showed higher CO₂permeability.With dry state measurements,CO₂permeability of 869 Barrer and a CO₂/N₂selectivity of 88.6,which surpassing the Robeson upper bound（2008）.Compared with the pristine Pebax membrane,the CO₂permeability and CO₂/N₂selectivity of the MMMs were increased by 9.2 times and 2.8 times,respectively.As for mixed gas humidification,the CO₂permeability and CO₂/N₂selectivity of the Co-BBP@POP-1 Pebax membrane（3 wt%）is 1409 Barrer and 83.At the same time,the effects of different temperatures and p H on membrane performance were explored.Compared with CA Pebax membrane,CFA-1 Pebax membrane showed more stable catalytic activity.This study deeply explores the application of biomimetic enzymes in the field of gas separation membranes,which provides a reference for the synthesis and application of biomimetic materials in the future.