Construction And Performance Research Of Composite Paper Based On Organic Framework Structure

Cellulose fiber,a biomass material with abundant reserves,green non-toxic,degradable,easy to modify,low cost,biocompatibility and excellent mechanical properties,has been given higher expectations in the current era.Cellulose based functional materials are prepared by means of selective oxidation,esterification,etherification,grafting,cross-linking,physical doping and other means.The special functions of light,electricity,magnetism,catalysis,adsorption and so on are given to cellulose derivatives,cellulose graft copolymers and cellulose gel,which can be divided into liquid crystal materials,adsorption materials,conductive materials,catalytic materials,photoelectric materials and so on.Organic framework materials are a major branch of crystalline porous materials.Hydrogen bonded frameworks（HOFs）,covalent organic frameworks（COFs）,metal organic frameworks（MOFs）and other materials have always attracted the attention of researchers.They have rich building elements,adjustable pore structures,and special functionality,It is widely used in gas storage,molecular recognition,fluorescence probe,catalysis,drug delivery and other fields,and can be used as active material to develop functional materials with cellulose fiber.However,the binding stability between such active substances and cellulose is still a problem.In this paper,in-situ growth and anchoring strategies are proposed.Based on cellulose based functional materials,organic framework materials are constructed on cellulose fibers by various means,and paper based proton conducting materials,flexible electrode materials and paper based photocatalytic materials are developed.These studies provide ideas for the expansion of cellulose based functional materials and effective suggestions for the high value-added application of cellulose.The main research contents of this paper are:（1）The composite paper for proton exchange membrane（PEM）was prepared by inducing the in-situ growth of HOFs composed of melamine and 1,2-ethanedisulfonic acid with cellulose fiber as the carrier.The results of scanning electron microscopy,X-ray diffraction,surface area analysis and contact angle measurement showed that cellulose fibers changed the particle state and hydrophilicity of HOFs.The regulation of cellulose fibers on HOFs improves the proton conduction efficiency of HOFs.The proton conduction value of composite paper formed by in-situ growth of HOFs on cellulose fiber is up to 6.46×10^–2 S·cm^-1 at 75°C and85%relative humidity。In addition,HOFs synthesized by ultrasonic or hydrothermal methods show differences in particle size and arrangement,which leads to differences in proton conductivity.（2）Using 2D porous DAAQ-TFP COF with redox active sites as an effective intermediate,through its C=N and amide bonds with dialdehyde cellulose（DACF）and graphene oxide（GO）,the three are organically combined into a series composite structure,and a paper based flexible electrode material with great application potential in the field of electrochemical energy storage is prepared.The DACF/COF-2 composite paper showed excellent specific capacitance(380 F·g^-1 at 1 A·g^-1),and the capacitance retention rate reached 94.6%after 10000 cycles of charging and discharging.In general,by means of stable chemical connection,we make full use of the super-large specific surface area and charge transport framework of GO,the high porosity and ion transport channel of DAAQ-TFP COF to build DACF/GO@COF paper-based electrode materials,which provides effective design strategies and successful cases for the development of cellulosic functional materials and the effective use of COFs in the field of electrochemistry.（3）With hyperbranched polymer（HPAMAM）,DAAQ-TFP COF and rGO were stably loaded on DACF and flexible paper electrodes were prepared.HPAMAM,as an effective linker,achieved covalent grafting of reduced graphene oxide（rGO）onto DACF through C=N and amide bonds.At the same time,the spatial steric hindrance generated by HPAMAM spherical branching network structure can induce DAAQ-TFP COF to grow stably and uniformly,thus realizing the load on DACF.The 2D pore structure of DAAQ-TFP COF is conducive to the ion transport of electrolyte solution,and the good conductivity of rGO promotes the electron transfer.The DACF-COF-rGO sandwich composite structure created by HPAMAM effectively promotes the utilization of redox sites in DAAQ-TFP COF by electrolyte solution and the charge transfer between DAAQ-TFP COF and rGO,so that the prepared DACF/HPAMAM/COF/rGO paper has superior performance.DACF/HPAMAM/COF/rGO composite paper has an area capacitance of up to 117.5 m F·cm^-2 at a current density of 0.2m A·cm^-2.And when the current density is expanded to 5 times or even 10 times,its area capacitance can still maintain 95.6%and 81.2%,and after 10000 cycles,it can still maintain95.2%of its initial capacity,which has the potential to apply and develop new flexible energy storage devices（4）Photocatalytic composite paper with stable loading of MOFs was constructed by using polydopamine（PDA）.The CF/PDA/MOFs composite structure was formed on the basis of cellulose fiber loaded with PDA by using the chelation effect of PDA on metal ions to induce the uniform growth of MOFs;The addition of PDA effectively controls the growth size and distribution of MOFs,and forms PDA/MOFs-Ⅱheterojunction,which effectively inhibits the recombination of photogenerated electron-hole pairs,so as to excite more superoxide radicals(·O^2-)and holes（h⁺）into the process of degradation of organic dye（rhodamine B）.Under the excitation of visible light,after 1 hour,CF/PDA/MOF composite paper showed a degradation rate of 77.2%for rhodamine B and had good cycle stability,which was more than twice as high as that of CF/MOF paper without PDA,showing great application potential and providing a new strategy for the development of paper-based photocatalytic materials.