Study Of Preparation And Application Of Inorganic-Organic Materials By "Seeds Embedded Epitaxial Growth" Strategy

Inorganic functional materials such as layered double hydroxides(LDHs),metal-organic frameworks(MOFs)and other functional materials have been widely studied and applied in many fields such as environmental treatment,catalytic separation and infrared absorption.However,these materials are usually put into use in the form of powders and particles.In the process of recycling and utilization,it is easy to cause blockage of channels,difficult to separate,and at the same time,easy to run off into the environment resulting in a secondary pollution.Inorganic-organic composites can combine the advantages of inorganic materials and organic materials,make the composites play the role of matrix materials,and use structural design to expand the application simultaneously.However,due to the difference of physical and chemical properties between inorganic and organic components,the stability of loads is often poor.At the same time,the inorganic surface is easy to be encapsulated by organic substances,which reduces the contact area and affects the performance.In view of the above problems and challenges,a synthetic strategy of "seed embedded-epitaxial growth" was proposed.A series of inorganic-organic composite fibers were prepared using electrospinning technology.By using the properties of inorganic and porous materials and immobilizing them after in-situ growth,inorganic powder materials were firmly fixed on organic fibers,and the contact area of powder materials was exposed to the greatest extent.Inorganic powder is not easy to lose and easy to recycle in application process.The application of this material in air purification,sewage treatment,and heat insulation were explored,showing excellent performance.This paper provided a reference for the preparation of inorganic-organic composite materials and the immobilization of powder materials,and was with potential theoretical value and application prospects.Specific research results were as follows:1.The method of preparing inorganic-organic composites by " seed embedded-epitaxial growth" strategy was described in detail.The preparation of PAN@LDH microspheres,PAN@LDH composite membranes and aerogel@LDH aerogels were achieved by this method.The structural stability of inorganic-organic composites was investigated in detail.It was found that during the in-situ growth of hydrotalcite,the"mortise-tenon structure" was formed between the LDH plates and the polymer fibers,which improves the stability of the load effectively.Furthermore,in order to explore the universality of this method,different kinds of LDHs and zeolitic imidazolate frameworks(ZIFs)materials were grown by changing the types of "embedded seeds".2.Controllable preparation of hydrotalcite-polyacrylonitrile composite fiber membranes:by tuning the amount of embedded hydroxyalumina(AlOOH),PAN@LDH with different loading percentage were achieved.The pore structure and air flux of PAN@LDH composite membranes with different LDH loading were investigated in detail,and air purification experiments were carried out.The particulate matter(PM)capture efficiency of PM 10 and PM2.5 reached 99.29±0.56%and 99.03±0.82%at high concentration of PM(?4000 ?g m-3).In particular,the PAN@60%LDH membrane showed outstanding removal efficiency for PM0.3?0.5 of 95.29 ± 1.95%too.The mechanism of PAN@LDH composite fiber membranes for particulate matter purification was explored.The in-situ growth of LDH plates can not only effectively enhance the pore size of the composite fiber membranes,but also introduce a large number of positively charged adsorption sites,which can improve the electrostatic adsorption efficiency of the membranes on the basis of reducing the air resistance of the membranes.The vertical growth of hydrotalcite prolonged the mass transfer path of particulates and increased the contact opportunity between PM and the composite membrane,which improved the efficiency of the capture of PM with different sizes.3.PVDF and PAN/AIOOH were electrospun by side-by-side spinning.The mechanical properties were improved by taking advantage of the melting point difference between the polymers,using PVDF as the thermal cross-linking component,and inorganic SiO2 fibers as the supporting material.A kind of aerogel-x@LDH composite fiber aerogel material was prepared by shear dispersion,freeze-drying and in-situ growth of LDH.At different temperatures,the thermal insulation performance of aerogels showed that the in-situ growth of LDH greatly improved the temperature differences of aerogel samples.Because of the strong infrared absorption peak of CO32-at 1360 cm-1,areogel-x@LDH achieves higher thermal insulation performance at 120?.The temperature difference of aerogel-20@LDH was 75.2?.The thermal conductivity of aerogel-20@LDH was 36.88 mW m-1 K-1,which was within the range of high-efficiency thermal insulation materials stipulated in the national standard.4.Two kinds of PAN@ZIF composite membranes loaded with ZIFs were prepared by using the strategy of "seed embedded-epitaxial growth"by taking zinc oxide as the "seed" and growth site.The adsorption experiments of naproxen,ciprofloxacin and tetracycline on the composite membranes were investigated in detail.The experimental data show that the adsorption process on the composite membranes for the three PPCPs can be assigned to the pseudo-second-order kinetics and Freundlich adsorption isotherm model.According to the PAN@ZIF isoelectric point and the pKa values of the three drugs,the electrostatic effect of PAN@ZIF on the adsorption process of the three PPCPs was not the main binding force.All three PPCPs contain benzene rings,which can form ?-?conjugation with imidazole rings in ZIF-8 and dia(Zn)structures.A large number of functional groups on the three drugs can form coordination with Zn2+on ZIF,thus effectively adsorbing on PAN@ZIF composite fiber membranes were achieved.