Preparation And Application Of Phosphazene-Based Hybrid Porous Polymers

Recently,environmental pollution caused by dyes,heavy metal ions,CO2 and radioactive nuclear waste(e.g.,129I,85Kr,127Xe)have caused certain impacts on both human health and environment.Among many methods for treating these pollutants,adsorption is widely used for removing pollutants,due to its low cost and simple operation.Hybrid porous polymers have good thermal and chemical stability,and are easy to modify,so they are extremely extensive used in adsorbents and have broad development prospects.The performance of adsorbents is not only affected by stability,but also depends on the pore structure parameters of materials(specific surface area and pore volume)and the type and amount of active sites in materials that can interact with guest molecules.Phosphazene and their derivatives are good units of preparing hybrid porous materials,because they have good thermal and chemical stability and solvent resistance.This paper used three different methods to prepare phosphazene-based hybrid porous polymers and studied their adsorption behavior for I2,CO2,heavy metal ions and dyes.The main contents are as follows:1.Hexaphenoxycyclotriphosphazene(OP)or hexaphenylcyclotriphosphazene(CP)as two typical cyclophosphazene monomers were selected as the initial raw materials.We were crosslinked the monomers with octavinylsilsesquioxane(OVS)by Friedel-C rafts reaction,and synthesized two parallel series of phosphazene-functionalized silsesquioxane-based hybrid porous polymers(PCSs).The structures of polymers were characterized by FT-IR,solid-state NMR and elemental analysis.It was proved that PCSs were successfully synthesized.TGA results showed that the obtained polymers had good thermal stability.N2 adsorption-desorption measurements showed the pore parameters of polymers,and the specific surface areas of polymers were 52.5-685.5 m2 g-1.The PXRD,FE-SEM and HR-TEM images confirmed that PCSs were amorphous materials.PCS-OP-3.with the highest surface area and its parallel series PCS-CP-3 were selected to further investigate their applications in adsorbing iodine vapor,dyes(CR and MB)and CO2.PCS-OP-3 showed better adsorption capacities than PCS-CP-3 for iodine vapor,CR,MB and CO2,which is mainly due to the pore structure and higher heteroatom content.In addition,the materials exhibit good recyclability and can be recycled at least 5 times.2.The phosphazene-based hybrid porous polymer(PCNP)was prepared by Knoevenagel reaction between 1,4-phenylenediacetonitrile and hexakis(4-formacylphenoxy)cyclotriphosphazene(HAPCP).A series of characterizations,such as FTIR,31P CP/MAS NMR,13C CP/MAS NMR and elemental analysis,were performed to investigate the structures of PCNP and proved the polymer was synthesized.TGA results showed that PCNP has good thermal stability.N2 adsorption-desorption measurements showed that the polymer has small specific surface area and mesoporous structure.The results of PXRD,FE-SEM and HR-TEM measurements have proved that PCNP is an amorphous material.The performance of PCNP in iodine vapor and dyes adsorption was studied.The calculated iodine adsorption capacity of PCNP was 0.97 g g-1;the adsorption capacities of CR,RB,MB and MO were 362,163,51 and 5 mg g-1,respectively.The results showed that PCNP has selective adsorption of dyes and preferential adsorption of large-size dyes.In addition,the material had good recyclability.3.The phosphazene-based hybrid porous polymer(PCAP)with Schiff base structure was prepared by hexakis(4-formacylphenoxy)-cyclotriphosphazene(HAPCP)and N,N-bis(2-aminoethyl)-1,2-ethylenediamine through aldimine condensation reaction.Through a series of characterization methods,the structures of PCAP was studied,which proved the polymer was synthesized.TGA results showed that PCAP has good thermal stability.N2 adsorption-desorption measurements showed that the polymer has mesoporous structure and small specific surface area.PXRD results showed that PCAP has a certain long-range order.The performance of PCAP on iodine vapor,heavy metal ions and dyes adsorption was studied.The calculated iodine adsorption capacity of PCAP was 4.6 g g-1,which was mainly attributed to the pore structure and high heteroatom content.The adsorption capacities of heavy metal ions Cu2+,Hg2+and Pb2+were 75,435 and 116 mg g-1,respectively.The adsorption capacities of CR,RB and MB were 440,155 and 11 mg g-1,respectively,and the material exhibited size selective adsorption,preferentially adsorbing large-size dyes.In addition,the material also showed good recyclability.