Preparation And Catalytic Properties Of Hierarchical Porous Polymers Based On Double Emulsion Template And Hyper-crosslinking Method

The organic porous polymers have good application prospects in gas adsorption,catalysis,chemical separation,and drug loading because of the high specific surface area,low-density framework and high chemical and physical stability.The polymers prepared through hyper-crosslinking by the Friedel-Crafts alkylation reaction have micropores and high specific surface area,and the mesoporous and macroporous organic polymers have been prepared using high internal phase emulsions templates.On this foundation,micron-sized hierarchical porous polymer particles with microporous,mesoporous and macroporous structure synthesized will have good value of applications in catalysis.In this paper,micron-sized polymer particles with macroporous and mesoporous structures were prepared by double emulsion template,and then micropores were constructed on the pore wall through hyper-crosslinking by the Friedel-Crafts alkylation reaction.Finally,hierarchical porous polymers were used to load An NPs and its catalytic performance was discussed.Firstly,the W/O/W double emulsions were prepared using styrene?St?and divinylbenzene?DVB?as monomers,and then porous crosslinked polystyrene-divinylbenzene?PS-DVB?particles were prepared by the polymerization initiated by azobisisobutyronitrile?AIBN?.Finally,microporous structures were constructed by Friedel-Crafts alkylation reaction to obtain polystyrene with hierarchical pores.The stability of high internal phase emulsions and the factors that affecting the particle size of PS-DVB particles were discussed.The particle size of PS-DVB particles was characterized by the particle size analyzer,the surface morphology of PS-DVB particles was characterized by the scanning electron microscope and the specific area and the pore size of PS-DVB particles were characterized by the automatic physical adsorption instrument.The results show that when the stirring speed reaches 800 r·min^-1,high internal phase emulsions can keep good stability,and the particle size of PS-DVB particles can be effectively controlled at 200 r·min^-1300 r·min^-1 during the preparation process of multiple emulsions.The specific surface area of hierarchical porous PS-DVB raises with the increase of DVB dosage,and when the content of DVB is 20%,the specific surface area can be up to 598.2 m²·g^-1.It shows that the microporous structure can be further constructed on the PS-DVB framework with mesopores and macropores by the hyper-crosslinking reaction,thus the hierarchical porous structure with micropores,mesopores and macropores will formed.In order to improve the polarity of the polymer framework and the loading capacity of nanogold,acrylic acid?AA?was added as the third monomer.The hierarchical porous polystyrene-divinylbenzene-acrylic acid?PS-DVB-AA?particles rich in polar carboxyl groups were still prepared by double emulsion templates and the hyper-crosslinking method.Then,gold nanoparticles?Au NPs?were loaded on PS-DVB-AA particles by thermal reduction reaction,and the catalytic performance of the loaded catalyst for the oxidation of benzyl alcohol and selective catalytic oxidation of benzaldehyde with H₂O₂ were studied.The morphology of the loaded catalyst was characterized by the scanning electron microscope,the specific area and pore size of the loaded catalyst were characterized by the automatic physical adsorption instrument and the the surface composition of the loaded catalyst was analyzed by the X-ray diffraction and the X-ray photoelectron spectroscopy.The results show that hyper-crosslinked PS-AA-DVB had hierarchical pores and its specific surface area can reached 784.5m²·g^-1.The surface of polymers is successfully loaded with Au NPs.With the increase of the concentration of chlorauric acid,the load of Au NPs on polymers increases correspondingly.The problem that Au NPs is easy to aggregate is well solved,and the composite catalyst has high catalytic activity in the oxidation of benzyl alcohol with H₂O₂ and selective catalytic activity of benzaldehyde.