Preparation And Applications Of Hybrid Porous Polymers Derived From Octavinylsilsesquioxane

Porous materials have become a research hotspot in recent years due to their excellent performance in the fields of catalysis,adsorption/separation,energy storage,and biomedicine.In particular,the emergence of new applications and the continuous improvement of their performance requirements are not only difficult and hot spots in the field of porous material research,but also opportunities and challenges for future development.Therefore,the research on the synthesis and application of porous materials has important scientific and practical value.Because of the rigid 3D cage-like structure,multi-functionality,easy modification and thermal stability,polyhedral oligomeric silsesquioxanes has become an ideal building unit for preparing hybrid porous materials.Thanks to its rigid core and adjustable peripheral functional groups,the hybrid porous materials based on cage silsesquioxane have developed rapidly in recent years and become an important branch in the field of porous materials.Their preparation methods are flexible and diverse,mainly including Friedel-Crafts reaction,Heck reaction,hydrosilylation,free radical polymerization,click reaction,as well as blending,doping,breath-figure method,etc.The porous materials prepared based on cage silsesquioxane are known for their excellent performance,including low density,high specific surface areas,excellent physical and chemical stability,good biocompatibility,and customizable performance.And they have been successfully applied to adsorption,detection,catalysis,water treatment,functional coating and other fields.Although considerable development of porous materials based on silsesquioxanes has been achieved,there are still certain problems,such as the high efficiency and versatility of the preparation method,the processability,the exploration of functions,and the expansion of applications of the final materialOctavinylsilsesquioxane(OVS),as one of the typical representatives of cage silsesquioxanes,is very suitable and flexible whether it is directly synthesized into porous materials or prepared after modification.Especially as a commercially available reagent,the systematic and in-depth research on it will help to further promote the industrial production and large-scale use of silsesquioxane materials.Porous polymers derived from OVS will give more possibilities to them and extend their applications.Therefore,the research on the development of synthetic methods and application exploration of porous materials derived from OVS is of great significance.In this thesis,OVS was selected as the target starting unit,to explore different preparation strategies for obtaining porous materials,and to study the properties and potential applications of them.The main contents of this paper are as follows:Chapter 1.The concept and properties of cage silsesquioxanes are introduced briefly,and the existing preparation strategies and application research of porous materials based on octavinylsilsesquioxane are summarized.Finally,the research significance and content of the topic of this thesis are expounded.Chapter 2.We have developed a simple and efficient method for preparing porous polymers based OVS through cationic polymerization initiated by AlCl3 at room temperature.The effects of reaction time,temperature and solvent on the polymerization process and the formation of pore structures were further discussed.The porosity of porous materials can be controlled within the range of 230～620 m2 g-1 of specific surface area.In addition,the post-functionalization of the obtained materials was further investigated by epoxidation,and the application of these polymers as carbon dioxide adsorbents(up to 0.98 mmol g-1)was studied and discussed in detail.This work fills the gap in the preparation of porous materials by cationic polymerization of OVS.Chapter 3.Silsesquioxane-based hexaphenylsilole-functionalized hybrid porous polymers were successfully synthesized by Friedel-Crafts reaction of OVS and 1,1,2,3,4,5-hexaphenylsilole.The polymers possess high specific surface area up to 1144 cm2 g-1,pore size distribution with both micropores and mesopores,good thermal stability and excellent fluorescence performance.In addition,the application of the polymers as fluorescent sensor for metal ion detection was explored.This sensing system exhibited fast response,good selectivity and sensitivity to Fe3+,Ru3+and Cu2+,especially for Fe3+,the quenching constant can reach 53695 L mol-1.The detection mechanism can be explained by electron transfer.The electron transfer between Fe3+,Cu2+ and Ru2+ and the silole units resulted in fluorescence quenching of the materials.These results indicated the broad application prospects of silsesquioxane-based porous materials in the field of metal ion detection.Chapter 4.A new type of hybrid nanoporous polymers were successfully prepared by Friedel-Crafts reaction using ladder-type silsesquioxane and OVS for the first time.The resulting materials possess good thermal stability and high specific surface area up to 1273 m2 g-1.At the same time,the nanoporous materials showed good adsorption capacity for dyes and heavy metal ions.The adsorption capacities of Congo Red and Pb2+ were up to 1883 mg g-1 and 301 mg g-1,respectively.The results showed that the adsorption behavior of the materials was in accordance with the Langmuir isotherm model and pseudo-second order kinetic model.Moreover,the materials showed good reusability,and the structure and performance were still maintained after 5 cycles.This work has further enriched the research on hybrid porous polymers derived from silsesquioxanes with different structures.Chapter 5.A series of triazine-functionalized silsesquioxane-based multifunctional porous materials were synthesized by Heck reaction using thiophene or phenyl-substituted triazines and OVS.The obtained materials showed high porosity,adjustable fluorescence performance,excellent thermal stability and efficient catalytic performance.Especially,the materials exhibited strong visible-light harvesting ability,anti-photoaging performance and superior photoelectric effect.Without the addition of oxidants and pH adjustment,the materials showed high photocatalytic activity for the degradation of both acidic and basic dyes(Congo Red,Rhodamine B,Methylene blue and SafranineT).And by adding sacrificial agents of different kinds of reactive oxygen species,as well as ultroviolet photoelectron spectrometer,X-ray photoelectron spectroscopy and other methods,the intrinsic photocatalytic mechanism was revealed.Due to their high specific surface area and the introduction of N atoms,the adsorption capacity for Pb2+ in water of the materials was up to 324 mg g-1.And their adjustable fluorescence property has also been successfully applied to the detection of nitroaromatics,with good selectivity and sensitivity.After 5 cycles of testing,the materials showed good regeneration ability without obvious performance degradation.This work provided great reference value for the synthesis of highly active,metal-free catalysts and multifunctional porous materials.