Nitrogen-containing Porous Organic Polymer Supported Metal For Catalysis In CO₂ And Epoxide Cycloaddition Reactions

Carbon dioxide（CO₂）is not only an important greenhouse gas but also a significantly attractive C1 source in modern chemical industry.Due to its low cost,abundance,non-toxicity,and non-flammability,the catalytic conversion of CO₂ has become a research focus.However,the chemical inertness of CO₂ still poses great challenges for its catalytic conversion.CO₂ cycloaddition reaction is a green and 100%atom-economical reaction,which holds promise as a prospective strategy to reduce carbon emissions by converting CO₂ into high-value cyclic carbonates.In this study,we designed and synthesized a series of novel porous organic polymers with advantages of simple synthesis,low cost,green,abundant micropores and hierarchical pore structure,high chemical stability,high specific surface area,and high CO₂ adsorption capacity.These polymers,as heterogeneous catalysts,exhibit excellent catalytic activity and high recyclability under mild conditions without solvent for the cycloaddition reaction of CO₂ and epoxides.Even at room temperature,ambient pressure,and diluted CO₂ conditions,these polymers still show excellent catalytic activity.The aim of this study is to develop green,low-cost,and efficient porous organic polymer heterogeneous catalysts,providing a convenient,environmentally friendly,and efficient approach to CO₂ conversion.Through this series of research results,we expect to provide innovative ideas for solving the problem of CO₂ emissions,and thus promote the continuous progress of new materials science research.The full text is as follows:（1）In the first part,by exploring the Scholl coupling reaction of bipyridine and o-phenanthroline with triphenylbenzene under different reaction conditions,we successfully synthesized conjugated microporous polymers Co-Bpy-POP and Co-Phen-POP with high specific surface areas.They exhibited excellent catalytic activity and high recyclability in the CO₂ and epoxide cycloaddition reaction under solvent-free,ambient pressure,and room temperature conditions,with turnover frequency（TOF）values of up to 250 h^-1 and 263 h^-1,respectively.Even under diluted CO₂ conditions at room temperature and ambient pressure,they still demonstrated excellent catalytic activity.（2）In the second part,we employed the Scholl coupling reaction and adopted the"killing two birds with one stone"strategy,utilizing aluminum chloride as both the catalyst for the Scholl reaction and the metal source for porphyrin metallation,successfully constructing directly metallated porous organic polymers,thus further reducing the cost.Al-Por-POP-1 and Al-Por-POP-2 catalysts demonstrated high yields,high TOF values,high recyclability,and broad substrate applicability in CO₂ cycloaddition reactions at room temperature and atmospheric pressure,with yields of 91.5%and 95.4%,and TOF values of57 h^-1 and 66 h^-1,respectively.（3）In the third part,we employed a one-pot method,successfully developing a novel cobalt-porphyrin-based conjugated microporous polymer microsphere at a lower cost.Co-Por-POP-1 and Co-Por-POP-2 catalysts possessed high specific surface areas and abundant microporous structures,enabling efficient CO₂ adsorption.Under mild conditions,these catalysts exhibited excellent catalytic performance and high recyclability,with yields of80.2%and 89.2%,and TOF values of 25 h^-1 and 26 h^-1 at room temperature and 1 MPa,respectively.（4）In the fourth part,we employed a strategy of in-situ polymerization of porphyrin on the surface of palm fiber activated carbon through the Scholl coupling reaction,which suppressed the Ostwald ripening phenomenon of the polymer particles.We successfully synthesized conjugated microporous nanosphere catalysts with particle sizes smaller than100 nm,high specific surface areas,and uniform dispersion,named Co-Por-XPFAC-3.This catalyst demonstrated efficient catalytic performance in the CO₂ cycloaddition reaction at room temperature and ambient pressure,with a TOF value of 195 h^-1.After 10 cycles of the reaction,the yield showed no significant decrease.Even when using diluted CO₂（15%CO₂in N₂）,Co-Por-XPFAC-3 exhibited high catalytic activity under the same conditions,with a TOF value of up to 87 h^-1.