Chain Shaped Imidazole Porous Organic Polymers Catalyze The Conversion Of Low Concentration CO₂ To Formamide And Quinazolone

In recent years,CO₂ emissions have exceeded the earth’s own purification capacity,leading to climate change and environmental issues.CO₂ emissions from industrial waste gases account for 60-70%of total CO₂ emissions,and chemical conversion of these waste gases has become an important research direction for CO₂ emission reduction technology.The conversion of low concentration CO₂ into formamide and quinazolone is a valuable synthesis pathway.Currently,there are few reports on the N-formylation reaction and three-component cyclization reaction of low concentration CO₂.Due to the complex gas composition,low CO₂ concentration,and stable chemical properties in the exhaust gas,it is necessary to develop catalysts with CO₂ enrichment and activation capabilities in order to achieve chemical conversion of low concentration CO₂.Imidazole porous organic polymers have the advantages of controllable structure,high specific surface area,abundant porosity,and nitrogen atom activation of CO₂.Therefore,we design chain shaped imidazole porous organic polymers as catalysts to convert 50%CO₂ into formamide and 30%CO₂ into 3-（tert butyl）quinazoline-2,4（1H,3H）-dione.The main content and results are as follows:（1）Preparation of chain shaped imidazole porous ion organic polymers for catalytic conversion of 50%CO₂ to formamide.A series of imidazole porous ion organic polymers were synthesized by copolymerization of different vinyl functionalized monomers with crosslinking agent DVB.The N-formylation of aniline with 50%CO₂ was used as a model reaction,and the catalytic performance of each catalyst in the reaction was tested.PIP-3showed the strongest catalytic activity,its performance and structure were characterized and analyzed,the results showed that PIP-3 had a pore structure and OH^-.The single factor method was used to optimize the reaction conditions.When 0.5 mmol of aniline,50%CO₂,2 mmol of phenylsilane,40 mg of PIP-3,and 1 m L of acetonitrile were reacted at room temperature for 24 hours,the optimal yield of formaniline was 87%.Varying the type of amine gave 21 formamide products in 39-95%yields.In anaerobic fermentation gas,9formamide products were obtained in 62-90%yield,and an 84%yield was obtained by amplifying the reaction 20 times.The catalyst maintained good catalytic activity during 5cycles.The reaction mechanism of the catalytic system is that OH^-in PIP-3 activates the Si-H bond of phenylsilane,then it reacts with CO₂ to generate formate ions and promote subsequent conversion to formamide.（2）Preparation of palladium loaded chain like imidazole porous organic polymers for catalytic conversion of 30%CO₂ to quinazolone.Chain shaped imidazole porous organic polymer POP was prepared by solvent thermal polymerization,and Pd（OAc）₂ was loaded to prepare Pd@POP.Characterization showed that Pd@POP has abundant porosity and good CO₂ adsorption capacity,and Pd was uniformly distributed in the polymer.Pd@POP was applied to the three-component cyclization reaction,and 3-（tert-butyl）quinazoline-2,4（1H,3H）-dione was obtained in the optimal yield of 95%when 0.3 mmol 2-iodoaniline,0.45mmol tert-butyl isocyanate,30%CO₂,10 mg Pd@POP and 2 m L superdry acetonitrile were reacted at 60℃for 18 h.Varying the type of 2-iodoaniline to obtain 8 quinazolone products in 50-95%yield.In the lime kiln waste gas,4 quinazolone products were obtained in 90-94%yield,and an 85%yield was obtained by amplifying the reaction 10 times.The catalyst could be recycled at least 5 times.The reaction mechanism is that 2-iodoaniline reacts with Pd active site to get intermediate,then tert-butyl isocyanate and CO₂ cyclize with intermediate and then protonates to get product.