Synthesis Of Functionalized Hollow Porous Nanospheres And Their Applications In Adsorption And Temperature-controlled Catalysis

In recent years,porous organic materials have been the focus of research in chemistry and materials field.Compared with traditional inorganic porous materials,it has high chemical and thermal stability,excellent chemical modificability,as well as a variety of pore structures and larger specific surface area.At present,there are many kinds of organic porous materials studied,among which,the hyper-crosslinked porous polymer has the advantages of a wide selection of monomers,a variety of synthesis strategies,and a design of morphology.As a new material,it has attracted much attention in the fields of organic compound/ion adsorption,supported catalysis,gas separation,drug transportation,fuel cell and so on.At present,the research on it is not comprehensive,such as how to specifically adsorb related pollutants,and how to add other self-control methods besides catalysis,there is still a great potential to be explored.This thesis mainly includes three chapters.The first chapter is the introduction,which mainly introduces the classification and application of organic porous materials,and focuses on the synthesis methods and functionalization strategies of hyper-crosslinked porous polymers,as well as the treatment background of heavy metal hexavalent chromium ion pollution and the development of thermo-sensitive smart materials.In chapter 2,a new type of hexavalent chromium ion adsorbent was designed and synthesized.Here,the polylactide-polystyrene-polyglycidyl methacrylate(PLA-b-PS-b-PGM)triblock polymer was used as the precursor to form the PGM-functionalized hollow porous nanospheres(HPNs-PGM)through over cross-linking mediated self-assembly,which were further modified with ethylenediamine(EDA)through ring-opening reaction to obtain the final adsorbent material(HPNs-NH₂).The morphology and properties of HPNs-NH₂ were measured by FT-IR,TEM,elemental analysis,BET and other tests.The results showed that HPNs-NH₂ has a regular hollow sphere structure,and the surface area calculated by BET is 627.071 m²/g,while the total pore volume is 1.588 cm³/g,and a load of N element of 3.239 wt%.The adsorbent was used to adsorb hexavalent chromium ions.This special multistage pore structure and a large number of amino and imino active sites in HPNs-NH₂ endow the material effectively improving the ability to capture Cr(VI).Therefore,the maximum adsorption capacity is up to 493 mg/g in a solution with p H=4,and after eight adsorption-desorption cycles,the adsorption capacity of HPNs-NH₂ can still maintain above 65%of the initial adsorption value.This remarkable adsorption capacity and excellent cyclic stability make HPNs-NH₂ have strong competitiveness compared with other porous adsorbents.These obvious advantages indicate that HPNs-NH₂ is expected to play a great potential in the treatment of hexavalent chromium in sewage.In chapter 3,a novel intelligent temperature-sensitive nano-responder is prepared.In this chapter,hollow porous nanospheres(HPNs)were formed by Friedel-Crafts alkylation reaction using polylactide-b-polystyrene(PLA-b-PS)as precursor.Then,by impregnation method,Pd nanoparticles were reduced in situ into the hollow sphere to obtain Pd@HPNs.Finally,poly(N-isopropylacrylamide)was used to modify the outer layer of the hollow spherical wall to obtain palladium loaded hollow nanospheres modified by PNIPAM(Pd@HPNs-PNIPAM).The morphology and properties of Pd@HPNs-PNIPAM were measured by BET,FT-IR,TGA,XRD,ICP,XPS and other tests.The results showed that the material was a hollow spherical structure with regular morphology,and the loading capacity of Pd nanoparticles was 3.41 wt%.After modification,the content of N element was 7.13 wt%.The reaction rate at 50 ^oC was2.5 times higher than that at 30 ^oC;In the contrast experiment,PNIPAM modified catalyst Pd@HPNs was used.Under the same experimental conditions,the reaction rate at 30 ^oC was the same as that of Pd@HPNs-PNIPAM,and the reaction rate at 50 ^oC was 6 times that of Pd@HPNs-PNIPAM.This indicates that the PNIPAM-modified catalyst material has excellent temperature control effect.After 5 cycles of varying temperature from 30 ^oC to 50 ^oC,the catalytic effect remained intact,which proved the reversibility of temperature sensitivity and good circulation.The nanometer responder can realize the spatial separation of metal and PNIPAM,which makes the switching control of the catalyst more sensitive and effective,and has a broad application prospect in the industrial application of some exothermic reactions.