Dynamic Imine Assembly Of Amino Functionalized Supramolecular Polymers And Their CO₂ Adsorption Properties

The large-scale combustion of fossil fuels has led to excessive CO₂ emissions,which in turn triggers a series of ecological and environmental problems such as global warming.CO₂ capture is a powerful measure to directly reduce carbon emissions from fossil fuels,the method for which mainly includes liquid ammonia absorption,membrane separation,and adsorption.The liquid ammonia absorption method has the advantages of high absorption rate,large capacity and simple operation,however,still suffers the disadvantages of easy volatilization,equipment corrosion,and large energy consumption;membrane separation method has the advantages of simple operation and low energy consumption,but has the disadvantages of difficult preparation and low separation efficiency.In contrast,the adsorption method,as a promising approach for CO₂ capture,has the advantages of good cyclic stability,simple operation,low energy consumption and high separation efficiency.The developed materials for CO₂ adsorption mainly include inorganic materials,covalent-organic porous materials,supramolecular organic porous materials,etc.Among them,supramolecular organic porous materials have superiority like simple preparation process,adjustable structure and easy functionalization.Moreover,amino-functionalization can further improve the materials’CO₂ adsorption performance based on the chemical interaction between amino groups and CO₂.Traditional methods for amino-functionalization mainly include covalent grafting,dipping and in-situ polymerization,but most of them have problems such as low grafting effiency,small adsorption capacity,poor recycling performance and complicated preparation process.Therefore,it is of great significance to explore more green and efficient methods to prepare materials with high CO₂ adsorption properties.Herein,this thesis aims to explore the construction of amino-functionlized supramolecular polymers through the interfacial self-assembly of di-amino-functional compounds and terephthalaldehyde.Based on the unique dynamic reversibility of dynamic covalent bonds,common amino compounds such as polyethyleneimine and tetraethylenepentamine are stably introduced through simple post-synthesis assembly to construct thermally stable supramolecular polymers.The introduction of amino groups provides abundant sites for chemical adsorption of CO₂.The dynamic imine assembly strategy has the characteristics of facile preparation,controllable structures and functions,which provides a new idea for the development of materials with high CO₂ adsorption properties.The main research content and results of this subject are as follows:（1）The supermolecular polymer PHP-x with abundant CO₂ adsorption sites was gently constructed by the interface assembly method through dynamic covalent bonding between di-amino-functional compound and terephthalaldehyde under atmospheric conditions.In addition,PHP-2 was modified with polyethyleneimine with varied concentration and time.It was found that the material midified with polyethyleneimine with the concentration of 121 mmol/g for 2h possesses a CO₂adsorption capacity of 6.70 cm³/g at 0°C,which is mainly caused by physical adsorption at low temperatures.（2）In order to further improve the CO₂ adsorption performance,the supramolecular polymer PHP-2 was modified with tetraethylenepentamine based on the dynamic reversibility of dynamic covalent bonding to construct a series of amino-functionalized supramolecular polymer material PHPT-x.Through adjusting the concentration,time and p H,optimal materials for CO₂ adsorption were selected.It was found that the material midified with tetraethylenepentamine with the concentration of1485 mmol/g for 8 h possesses a CO₂adsorption capacity of 27.79 cm³/g at 80°C.Compared to PHP-2,the improvement of CO₂ adsorption performance of the modified supramolecular polymer is mainly due to the successful introduction of abundant amino sites for chemical adsorption of CO₂...