Synthesis Of Conjugated Micro- And Mesoporous Metalloporphyrin Polymers And Their Catalytic Performance For Applications

Metalloporphyrins are of great concern by researchers for its unique structure and excellent properties.Especially as an excellent biomimetic catalyst in the catalytic field,metalloporphyrin are widely researched because its similar structure to the active center of cytochrome P450 enzyme,also functions similarly while being green,efficient,environment-friendly and reactive under mild conditions.But metalloporphyrin is limited used because it is easily degraded by the high concentration of peroxide produced in the reaction system.So it is hardly separated from solvents at the end of reaction,leading don't be recycled.The one-time consumption of the catalyst increase the will cost of the production in practical application,and the residual of the metalloporphyrin decomposition products will also impact the purity of the oxidation products.Therefore,in order to solve the problem metalloporphyrin in the homogeneous catalytic reaction,metalloporphyrin is aggregated into a special structure of metalloporphyrin polymer with stable chemical properties and excellent catalytic performance,which has been a very competitive frontier.Based on the current research progress of conjugated microporous and mesoporous polymers?CMPs?we are interested in whether we can synthesize conjugated micro-and mesoporous metalloporphyrin polymer with monomer metalloporphyrin as building blocks.Conjugated micro-and mesoporous metalloporphyrin polymer will have an excellent catalytic performance and more stable chemical structure.On the one hand,the insoluble macromolecule metalloporphyrin polymers can achieve the heterogeneous catalysis application of metalloporphyrin.On the other hand,owing to the synergistic effects of porous structure and conjugated covalent structure,the catalytic activities of metalloporphyrins in the reaction and the selectivity of the target products will be improved tremendously.On the basis of large number of research literature,we synthesized the Mn?III?5,10,15,20-Tetraksi?4'-bromophenyl?porphyrin?[p-Br]₄PMn?and the suitable Mn?III?5,10,15,20-Tetraksi?4'-ethynylphenyl?porphyrin?[p-ethynyl]₄PMn?as template.So conjugated metalloporphyrin polymers?MnP-AMP?was synthesized based on Buchwald-Hartwig aromatic amination reaction with p-phenylenediamine and[p-Br]₄PMn as building blocks;alkynylporphyrin conjugated organic polymer?MnE-TPP?was synthesized by Sonogashira coupling reaction with[p-ethynyl]₄PMn and[p-Br]₄PMn as building blocks;conjugated metalloporphyrin polymers?PP-EPMn and PX-EPMn?were synthesized by the Sonogashira coupling reaction with[p-ethynyl]₄PMn as building block,phenylene and xenyl groups as bridges.The polymers have as high as 300 m2/g surface area and a relatively concentrated microporous mesopore distribution.FE-SEM images showe that the monoliths consist of 100-400 nm sized layer structure,while PP-EPMn and PX-EPMn have special nanosphere structures with diameters of 150-400 nm.MnE-TPP was used as a catalyst to catalytic oxidation-C-H of toluene under mild conditions.By studying different factors in the reaction,such as the effect of reaction pressure,reaction temperature,the concentration of the catalyst and the flow rate of air.The results showed that when the reaction is catalyzed at 160?,0.8 MPa with the air flow rate being 1000 mL/min,the conversion of toluene is up to 9.7%,total yield of benzaldehyde and benzyl alcohol is 7.16%and the yield of acid is 1.24%after 4 h reaction,the selectivity to total benzaldehyde and benzyl alcohol is 74.0%.The results are better than that of[p-Br]₄PMn and[p-ethynyl]₄PMn catalytic oxidation of toluene in the same reaction conditions.And MnE-TPP can be recovered by simply centrifugal separation.After 5 cycles,the recovered MnE-TPP catalyst remained highly active that the conversion rates of toluene remained 9.1%with 70%total benzaldehyde and benzyl alcohol selectivity.While the catalyst of[p-ethynyl]₄PMnCl and[p-Br]₄PMnCl are only once used in the same reaction conditions.MnP-AMP was applied to the catalytic oxidation of alcoholic hydroxyl group because it is rich in-C-N-groups which enhanced the polarity and readily reacted with alcohol compounds.We studied the effects of the pro-oxidant,solvent and temperature on the catalytic oxidation of benzyl alcohol.The results showed that isobutyraldehyde as a pro-oxidant is essential in the reaction,and the polar solvent acetonitrile which contain N atom can promote the reaction.MnP-AMP catalyzed the selective oxidation of benzyl alcohol to benzaldehyde under mild condition at 40?.The conversion of benzyl alcohol can up to 99%and the selectivity of benzaldehyde can up to 98%in 2 h.We have extended the kinds of alcohol to fatty alcohols that more than 4 carbon atoms,a variety of substituents of aromatic alcohols and cycloalkyl alcohol that MnP-AMP also showed a good catalytic effect.The[p-Br]₄PMnCl was polymerized into a complex MnP-AMP by a coupling reaction.And MnP-AMP was applied to the catalytic oxidation of alcoholic hydroxyl group which achieved a more extensive and valuable application of metalloporphyrins.This provides a new idea for the biomimetic catalytic applications of metalloporphyrin.PP-EPMn and PX-EPMn with new a nanospheres structure were synthesized by coupling the[p-ethynyl]₄PMn with rigid alkynyl and rigid phenylene or xenyl.The rotation of alkynyl group and the steric hindrance of xenyl or phenylene groups lead to the higher distortion of polymer mesh and chain during polymerization process,which result in the nanospheres structure of polymers.The nanospheres can dispersed in water easier than that of porphyrin.So PP-EPMn and PX-EPMn were applied to the catalytic oxidation of methylene blue in water.The two polymers can applicable to degrade methylene blue at pH value 4-14 which are superior to Fenton reagents only work in acidic condition.Especially in the alkaline solution methylene blue can be completely degraded for few minutes.In addition,we have recycled these catalysts and found that the structure of polymers is stable,not easily broken down to destruction.The recovery rate can reach more than 88%and the reuse performance decreased little.