Conjucated Microporous Polymer Based On Carbazole Structure: Synthesis,Characterizition And Application

Compared with traditional porous materials,a new type of porous organic materials possesses strong structural controllability and designability,thus showing their advantages and attractive prospects in the fields of adsorption and separation,catalysis,energy storage,electrochemical devices,and so on.Among them,conjugated microporous polymers（CMPs）have attracted much attention due to their unique rigid conjugated skeleton and stable physical and chemical structure.CMPs are three-dimensional（3D）semiconducting polymers with a microporous skeleton bearing aπ-πconjugated structure.Theoretically,countless kinds of CMPs with diverse structures and functions can be constructed via the reasonable combination of different kinds of molecular building blocks as monomers of CMPs with synthetic reactions.Therefore,the structural diversity of monomers for CMPs is really crucial to the implementation of this process.However,in the current studies of CMPs,the structure and type of available monomers are very limited,which greatly restricts the development and application of functional CMPs.In this work,we have carried out a series of studies on this issue.The main contents and results are as follows.1.A novel carbazolyl-containing building block for CMPs,3,6-dibromo-9-（4-bromophenyl）-9H-carbazole（CZ）,was successfully designed and synthesized,and then a new type of CMP based on carbazole structure,CZ-TEB,was synthesized via the Sonagashira coupling reaction between CZ and 1,3,5-triacetylenyl benzene（TEB）.The BET specific surface area of CZ-TEB can reach 1600 m² g^-1.It has an amorphous layered microstructure and a wide pore size distribution covering both micropores and mesopores.Besides,CZ-TEB exhibits an excellent thermal stability.2.Using CZ-TEB as a support material,the ultrafine silver nanoparticles were uniformly loaded onto its surface of CZ-TEB via an in-situ reduction method,thereby preparing a new heterogeneous nanocatalyst,Ag⁰@CZ-TEB.The catalytic reduction degradation of nitrophenol and its derivatives was selected as a model reaction for investigating the catalytic performance of Ag⁰@CZ-TEB.The studies indicate that Ag⁰@CZ-TEB possesses high catalytic efficiency and the normalized rate constant(k_nor)for the reduction reaction of 4-nitrophenol to 4-aminophenol can reach up to 21.49 mmol^-1 s^-1.This result is better than most of the comparable heterogeneous catalysts reported so far.Based on the exploration of the substrate scope for the model reaction catalyzed by Ag⁰@CZ-TEB,a"Capture–Release"model was proposed to shed light on the high catalytic efficiency of the Ag⁰@CZ-TEB nanocatalyst by comprehensively considering the structural characteristics of Ag⁰@CZ-TEB,the matching relationship between its channel size and the size of substrate molecules,and the hydrophilic-hydrophobic behavior of CZ-TEB skeleton.The“Capture–Release”model can provide theoretical support for constructing heterogeneous catalysts using porous organic materials as supports.In addition,Ag⁰@CZ-TEB can still maintain a catalytic efficiency of up to 90%after the five consecutive runs,thus exhibiting excellent recyclability and reusability.3.Another novel carbazolyl-containing building block for CMPs,3,6-2-acetenyl-9-（4-acetylene phenyl）-9H-carbazole（ECZ）,was obtained through scientific molecular design and synthesis.And new CMP materials,ECZ-DBDO and ECZ-DBDO-SO3H′,were constructed via the Sonagashira coupling reaction of ECZ with 2,5-dibromo-1,4-dihydroxy benzene（DBDO）and 3,3’-（（2,5-dibromo-1,4-phenylene）bis（oxy））bis（propane-1-sulfonic acid）,respectively.On this basis,an amphipathic CMP,ECZ-DBDO-SO3H,was prepared by the sulfonation of phenolic hydroxyl groups on the ECZ-DBDO skeleton with 1,3-propane sulfone（1,3-PS）.Since the resonance balance between p-phenol and p-benzoquinone in ECZ-DBDO will reduce the reactivity the phenolic hydroxyl groups,only about 20.6 wt%of ECZ-DBDO was successfully modified by 1,3-PS.The as-prepared ECZ-DBDO,ECZ-DBDO-SO3H and ECZ-DBDO-SO₃H′possess a BET specific surface area of 589 m² g^-1,393 m² g^-1 and 277 m²g^-1,respectively.These CMPs are in the form of amorphous packed fragments and have a discontinuous lamellar microstructure and a wide pore size distribution covering both irregular micropores and mesopores.Similar to CZ-TEB,they also exhibit a good thermal stability.4.The modified copper foam with alkyne groups on its surface,Cu-≡,was prepared by the nitric acid activation of an original copper foam as a substrate,followed by the chemical treatment with silane coupling agent bearing ethynyl group.Then,the ECZ-DBDO-SO3H coating was constructed on the surface of modified copper foam via the in-situ coupling reaction of ECZ and DBDO on the surface and the subsequent sulfonation reaction,thus successfully designing and preparing a kind of unique modified copper foam with the surface modified with a hydrophilic CMP material ECZ-DBDO-SO3H,Cu-CMP-SO3H.Our studies indicate that Cu-CMP-SO3H is an interesting material with unique amphiphilic surface,and its surface can still maintain a good amphiphilicity under the action of acid,alkali,and long-term air/natural light irradiation.According to the structural characteristics of ECZ-DBDO-SO3H as a surface modifier,and combined with the experimental observations and results,we speculate that there exist hydrophilic and lipophilic channels in Cu-CMP-SO3H.Based on this,a hydrophilic-lipophilic dual-channel model is proposed,which is different from the previous hydrophilic or hydrophobic interface model.This model can give a reasonable explanation to the super-amphiphilicity of Cu-CMP-SO3H,and is expected to lay a theoretical and practical basis for designing and fabricating novel materials having a super-amphiphilic surface.