Synthesis And Adsorption Properties Of Ferrocene-Based Organosilicon Porous Polymers

Porous organic polymers have attracted great attention because of their low density,high specific surface area,excellent physical and chemical stability and easy design.The main efforts in this area focus on the synthesis of new functionalized porous materials and their applications in the fields of gas adsorption,gas separation,catalysis and photoelectric materials in recent years.Due to the ideal inorganic-organic hybrid structure,organosilicon materials have been widely applied in chemical industry,transportation,machinery manufacturing,construction and so on.However,the research on organosilicon porous polymers is relatively few.Compared to conventional organic carbon porous materials,organosilicon porous polymers have many advantages,such as facile monomer synthesis,higher thermal stability,and easy achievenment of high surface area.Ferrocene is a chemical regeant and its derivatives have been widely applied in many areas,such as electrode modification,functional material and iosensor technology because of the internal special electronic structure which endows ferrocene lots of excellent performance.Up to now,ferrocene-based porous polymers have been rarely reported and the results showed that ferrocene-based porous polymers have great potential for CO₂ and H₂ adsorption.Therefore,the design and synthesis of new ferrocene-based organosilicon porous polymers will become a rapidly evolving field.Herein,we combine the advantages of ferrocene and tetrahedral silicon-centered precursors,and have synthesized several novel ferrocene-based organosilicon porous organic polymers by different coupling reactions.The structure,thermal stability and pore properties of the resulting porous polymers have been analyzed by FTIR,13 C CP/MAS NMR,29?1?Two novel ferrocene-based porous organic polymers,FPOP-1 and FPOP-2,have been synthesized based on 1,1'-dibromoferrocene and tetrahedral silanes via Sonogashira coupling reaction.Compared with other porous polymers,these polymers exhibit excellent thermal stability?decomposition temperature: 415??and moderate Si CP/MAS NMR,elemental analysis,TGA,nitrogen desorption/desorption isothermal and so on.Moreover,their gas adsorption properties were also studied.The details are shown as follows: porosity with the highest BET surface area of 542 m²/g and total pore volume of 0.68 cm³/g.It is found that the porosity of the porous polymers can be effectively adjusted by changing the length of the building monomers.In addition,the CO₂ adsorption capacity?1.38 mmol/g at 273 K/1.0 bar,0.75 mmol/g at 298 K/1.0 bar?,H₂ adsorption capacity?0.91wt% at 77 K/1.0 bar?,CO₂ adsorption heat?31.1 kJ/mol?and CO₂ selective adsorption?CO₂/N₂: 17.61 at 298 K/1.0 bar?of two porous polymers are comparable to some organic porous polymers with higher surface areas,which may be due to the withdrawing electron property of internal ferrocene groups.?2?In order to study the relationship between the crosslinking reaction types and porouse properties,we have synthesized two porous organic polymers?FPOP-3 and FPOP-4?based on 1,1'-divinylferrocene and silicon-centered monomers,i.e.,tetrakis?4-bromophenyl?silane and tetrakis?4-bromodiphenyl?silane via Heck coupling reaction.The highest BET surface and pore volume of these porous polymers is 499 m²/g and 0.49 cm³/g.Compared with the formed triple bond in Sonogashira coupling reaction,porous materials by Heck coupling reaction possess ethylene with a extent of flexibility,resulting in a small decrease of the porosity.For applications,their CO₂ adsorption heat?32.9 kJ/mol?is relatively high and can be applied in CO₂?3?In order to study the relationship between the number of linker sites of the silicon-centered units and porous properties,we have synthesized two porous organic polymers?FPOP-5 and FPOP-6?from 1,1'-diethynylferrocene and tri-or tetra-bromophenyl containing silanes via Sonogashira coupling reaction.The materials exhibited high porosity with the highest BET surface area of 954 m adsorption.2/g and the total pore volume of 0.74 cm³/g?FPOP-6?.These results reveal that their porosities could be tuned by changing the number of linker sites of the silicon-centered units,and it is easier to construct high-surface-area porous organic polymer based on tetrahedral silanes.FPOP-6 exhibits excellent gas storage capacities among the polymers with the same surface area such as 2.35 mmol/g and 1.31 mmol/g of CO₂ at 273 K/1.0 bar and 298K/1.0 bar,and 6.87 mmol/g of hydrogen at 77 K/1.0 bar.These results indicated that the introduction of ferrocene monomer into porous framework is a promising strategy for enhancing gas adsorption property,and these polymers could be a promisingly applied in gas adsorption and separation.