Triazine-based Organic Polymer For Carbon Dioxide Capture And Catalytic Conversion

Nowadays,anthropogenic CO₂ emission from industrial burning of fossil fuels has been considered as the main source of greenhouse gas to pay most of the responsibility for climate changes.On the other hand,it is noteworthy to mention that CO₂ could also act as a cheap,nonflammable,nontoxic and renewable C1 building block for organic synthesis.Therefore,extensive efforts are constantly devoted to CO₂ capture as well as its catalytic conversion in view of both ecological safe and economic efficiency.Porous organic polymers?POPs?have been recognized as promising candidates for both gas storage and solid catalyst support owing to their large specific surface area,tunable porosity,high chemical stability and well structural diversity.Consequently,the integration of both CO₂ capture and CO₂ catalytic conversion processes by POPs could reveal particularly effective for preserving considerable volumes of CO₂ emission,and at the same time,providing scientific motivation for transformation of waste CO₂ into useful chemicals.The present thesis aims to develop new types of nitrogen-rich POPs derived from 2,4,6-trihydrazinyl-1,3,5-triazine?THTZ?precursor for selective adsorption of CO₂ through dipole-quadruple interactions and repulsion of N₂ by vast hydrazinyl linkages as well as subsequent fixation of CO₂ by massive hydrogen bond donors to activate the substrates,rendering a cascade strategy for sequential capture and utilization of waste CO₂ as a sustainable C1 resource for chemical transformations.The main contents are as follows:?1?HB-CTP-1 is synthesized through a simple nucleophilic substitution reaction of THTZ with cyanuric chloride promoted by Na₂CO₃ at 110°C.It mainly exists in aggregate form possibly due the strong hydrogen bonding interactions between triazine network layers,which results a reversible type-II N₂ isotherm that tend to proceed through unrestricted monolayer-multilayer adsorption with low BET surface area and total pore volume as 51.2 m²/g and 0.28cm³/g respectively.However,the HB-CTP-1 material has shown good CO₂ capture capacity?1.86 mmol/g,8.2 wt%?at 273 K and 1 bar conditions,and it could still exhibit satisfactory capture performance after at least five consecutive adsorption and desorption cycles,rendering good recyclability.Moreover,such polymer could be employed as metal-free heterogeneous catalyst for the cycloaddition of CO₂ with various epoxides under mild and solvent-free conditions,affording cyclic carbonates in high yields.The resultant HB-CTP-1 can be reused at least five times without significant loss of its catalytic activity.?2?HB-CTP-2 and HB-CTP-3 are synthesized by dehydration condensation between THTZ and dianhydrides at high temperature.They possess much better CO₂ adsorption capacity under 273 K and 1 bar conditions?10.5 wt%and 9.0 wt%respectively?,and the selectivities for CO₂ at 273 K are calculated as high as 307?HB-CTP-2?and 258?HB-CTP-3?.By using Virial equation through CO₂ adsoprtion data fitting,the limiting heat of adsorption for HB-CTP-2 and HB-CTP-3 could be calculated as 39.0 kJ/mol and 38.6 kJ/mol respectively.Furthermore,the heterogeneous HB-CTP-2 and HB-CTP-3 exhibit high catalytic activity and reusability for cyclo-addition of CO₂ with aziridines under mild conditions with excellent tolerance to a wide range of functional groups.