Preparation Of Porous Organic Polymers Via Interfacial Azo-Coupling Polymerization And Their Applications In Membrane Materials

Porous organic polymers are widely used in separation,purification,energy,catalysis and other fields due to their considerable specific surface area,continuous pore structures,various structural designs and flexible preparation methods.Porous organic polymers are considered to be the new generation of materials that can break the constraints of selectivity and permeability of membrane materials due to their specific pore channel properties.However,most porous organic polymers have highly crosslinked framework structures,which make them are difficult to prepare into membranes by solution method or melt processing.This issue greatly limits the application of porous organic polymers in membrane separation materials.The method of interfacial polymerization can directly prepare porous organic polymer membrane material at the interface in one step,which can avoid the processing problems caused by insolubility.This paper innovatively proposes some methods that can prepare porous organic polymer thin film materials through diazo coupling reaction at the interface.Through the various structural design and functional control of monomers,high-performance membrane materials with different pore properties and functionalities can be prepared.The details are as follows:1.By using the high reactivity of the coupling reaction between the diazonium salt reagent and the phenolic monomer,the diazonium salt reagents were dissolved in the water phase,and the phenols were dissolved in ethyl acetate.When the two phases are in contact,a porous organic polymer membrane can be rapidly formed at the waterethyl acetate interface.The obtained membranes have high specific surface areas,various specific surface areas and different pore sizes.In addition,a large number of nitrogen and oxygen functional groups were existed in the framework,palladium nanoparticles can be anchored by membranes and therefore served as membrane catalytic reactors,which displayed good catalytic performances for nitrophenol.The prepared Pd loaded membranes displayed a high catalytic performance for nitrophenol reduction with a flux of 27.3 t m-2 day-1.2.Based on the previous work,thinner porous organic polymer membranes were achieved by changing the organic phase to butyl butyrate,which is less compatible with water,and shortening the reaction time.In addition,four kinds of membranes with different specific surface areas and different pore sizes were prepared by adjusting the monomers.The prepared membrane material could be further used as supports for the interface polymerization of polyamide membranes.It was found that the pore sizes of the porous organic polymer interlayers had a great influence on the performance of the overall composite membranes.Among the prepared nanofiltration membranes,an interlayered membrane with suitable pore size displayed a flux of 32.2 L m-2 h-1 bar-1 with high salt rejection rate.3.Based on the high water-swelling ratio of commercial Nafion membranes,the diazonium salt reagents solution could be easily penetrated into the swollen Nafion membrane.Subsequently,an interfacial azo-coupling polymerization was occurred on the surface of Nafion membrane and resulted a porous organic polymer protective layer.The prepared protective layer made the composite Nafion membrane show a lower swelling ratio and lower methanol permeability without the decline of proton conductivity.The swelling ratio of composite Nafion was improved from 25.1%to 9.1%,and the methanol permeability was improved to 1.92 × 10-7 cm2 s-1.4.Diazo coupling polymerization at the interface is not limited to the macroscopic interface,but can also occur at the micro-phase interface.Two-dimensional nanosheet materials were prepared at the microphase interface by vigorous stirring.In addition,the regularity,as well as the thickness,of the nanosheets could be improved by the introduce of surfactants.The prepared nanosheets can be doped into polybenzimidazole to prepare high-temperature proton exchange membranes.The nanosheet-doped membranes had high phosphoric acid doping rate and exhibited enhanced phosphoric retention abilities,which provided the approach to preparing high-performance,high stability high-temperature proton exchange membranes.This work provided a novel strategy to prepare porous organic polymer membranes with interfacial diazo-coupling polymerization which is facile-process and time-saving.In addition,the combination of polymer organic polymer and membrane technique provide promising research directions to achieve high diversity of membrane architectures and functionality.