Synthesis Of Porous Organic Polymers And Their Applications In CO₂ Conversion And Proton Conduction

With the development of human society,the global energy demand continues to increase.At present,the energy supply is still dominated by fossil fuels,which not only leads to the depletion of global non-renewable energy sources,but also causes environmental problems such as global warming caused by the rapid increase in CO₂concentration.Therefore,developing clean energy and regulating CO₂ concentration has become a major issue related to global ecological stability.It is an effective strategy to adjust the proportion of energy use from the source,vigorously develop renewable energy such as hydrogen energy,wind energy,solar energy,etc.,and capture and store CO₂ in the atmosphere and further convert it into industrial chemicals and low-carbon fuels.Porous organic polymers(POPs)linked by covalent bonds are a class of lightweight porous network materials with high specific surface area,good stability and extensive synthesis methods.With the continuous development of organic building unit types and synthetic methods,POPs show high flexibility in structural design.Therefore,the development of POPs with high activity,high stability and easy modification for CO₂ capture,catalytic conversion and new energy development and utilization will have great potential.We design and synthesize porous organic polymer materials with salen and pyrazine functional groups in a function-oriented manner and apply them in CO₂ catalytic conversion and proton conduction applications.The main research results of this thesis are as follows:1.A series of metal-salen functionalized porous organic polymers(M-salen-POP,M=Mn²⁺,Co²⁺,Ni²⁺)were synthesized through simple metal-assisted methods.Together with porous nature and presence of many active catalytic sites which come from Lewis acidic metal ions in the framework,Co-salen-POP could exceptionally catalyze the cycloaddition reaction of CO₂ and styrene oxide to obtain 96%yield and99%selectivity within 30 minutes under 100°C and 1 MPa CO₂ atmosphere.After five cycles,its catalytic yield of styrene carbonate can be maintained at 94%under the same condition.Furthermore,other epoxides such as epichlorohydrin and phenyl glycidyl ether can be completely converted in 5 minutes at 100°C and 1.0 MPa.The present work offers a facile,powerful and efficient strategy to construct high-efficient heterogeneous catalysts with abundant active sites in the fixation of carbon dioxide.2.Fully conjugated pyrazine-rich composites Cr₁/HT-CMP1 and Cr₁/HT-CMP2were prepared via K₂Cr₂O₇-assisted oxidation by a one-pot cascade method and investigated as heterogeneous catalysts for photocatalytic CO₂ reduction application.Due to their suitable pore structure and excellent stability,Cr₁/HT-CMP1 and Cr₁/HT-CMP2 can be used as ideal carriers for CO₂ adsorption,activation and photo-generated electron transfer,showing high catalytic efficiency in photocatalytic reduction of CO₂reduction.The CO yields reached 14.6 and 17.9 mmol g^–1 within 3 hours,respectively,with a selectivity of 99%.3.The pyrazine-linked conjugated microporous polymers(CMPs)have been developed according to a one-pot strategy in large scale under an autoclave.The obtained HD-CMP not only exhibited extended?-conjugated structures,suitable surface areas,exceptional chemical stability toward harsh conditions but also the nitrogen sites on the pyrazine functional groups could serve as binding sites to anchoring the H₃PO₄ as proten carriers.Furthermore,hydrophobic angle measurements and water adsorption isotherms indicated high water uptake capacity and hydrophilicity property of H₃PO₄@HD-CMP.Attributed to these features,the resulting H₃PO₄@HD-CMP exhibited ultrahigh proton conductivity of 1.05×10^-1 S cm^-1 at 80?under 100%RH,which was comparable to most materials currently reported.