| Metal-organic framework（MOF）is an emerging family of highly porous crystal compounds.Its ultra-high specific surface area and porosity provide an excellent platform for adsorption and separation of all kinds of pollutants from water.The application of excellent physical and chemical properties and structural diversity of MOF in special environment provides more plastic space and shows great potential for water purification.However,the inherent micro-powder morphology and fragility of MOF,as well as insoluble and infusible,lead to its poor formability,which is not conducive to recycling,which limits their practical application in water treatment.In order to obtain macroscopic MOF monolithic materials which are easy to be recycled,it is an effective way to prepare MOF monolithic aerogels by compounding MOF and polymer materials.Therefore,taking the above contents as the starting point,this paper focuses on the composite process of water-stabilized MOF and natural or non-toxic polymers and the adsorption performance of the prepared MOF monolithic aerogel adsorbents for representative pollutants in water.Through the selection of physical and chemical properties,synthesis conditions and suitability of polymer materials of MOF,a series of high performance MOF composite aerogel adsorbents were prepared,and their adsorption properties and adsorption mechanism for antibiotics,heavy metal ions,organic dyes or organic pesticides were studied in detail,in order to prepare water treatment adsorbents that are easy to synthesize,efficient,cheap and recyclable.It contributes to the forming and processing of MOF and the development of new composite adsorbents.The specific content is as follows:1.The selection of cheap and scalable MOF and gel substrates is particularly important for the follow-up development of MOF monolithic aerogels that can be used in engineering.Cellulose（CE）is the most abundant linear polysaccharide in nature.It is green,renewable,biodegradable,cheap and easy to obtain.It is an excellent substrate for the preparation of aerogels.The synthesis process of ZIF-67 is mild,easy to operate,high yield and excellent adsorption capacity for tetracycline.Firstly,cotton fiber was dissolved in alkaline water system,and single-network regenerated cellulose hydrogel was obtained by covalent cross-linking at room temperature with epichlorohydrin（ECH）as cross-linking agent.3D macroporous regenerated cellulose aerogel（RCA）was obtained by freeze-vacuum drying technology.3D multi-porous ZIF-67 regenerated cellulose aerogel（ZIF-67/RCA）was obtained by in-situ growth of ZIF-67 at room temperature,and the loading rate of ZIF-67 is 25.39%.In order to improve the loading rate of ZF-67 on RCA,the layer polyaniline（PANI）was promoted by in-situ polymerization at low temperature on aerogel surface.Further prepared 3D multistage pore material:ZIF-67/PANI/RCA,and the loading rate of ZIF-67 increase to 42.38%.The equilibrium adsorption capacity of 3D multi-porous ZIF-67PANI/RCA for tetracycline is 409.55 mg·g-1.2.The preparation of MOF composite aerogels based on biological substrates instead of non-biocompatible or degradable polymer materials is the inevitable development direction of environmental protection and sustainability.Chitosan is the second most abundant natural polysaccharide after cellulose,and its linear molecular chain is rich in NH2,soluble in acids and bases.The preparation of biological aerogels by chemical cross-linking has inherent advantages.NH2-Ui O-66 has high specific surface area,good thermal stability,excellent water stability,similar to primary ammonia in chitosan molecule,easy chemical cross-linking,and is an excellent adsorbent for heavy metal ions.Single network NH2-Ui O-66/chitosan monolithic hydrogel（NH2-Ui O-66/GCH）was prepared for the first time by dissolving chitosan in acidic water system,blending NH2-Ui O-66 as building unit and glutaraldehyde as cross-linking agent.3D multiporous NH2-Ui O-66/chitosan monolithic aerogel（NH2-Ui O-66/GCA）was obtained after freeze-vacuum drying.The prepared 3D multi-porous NH2-Ui O-66/GCA has ultra-light properties,the density is only 15.8 mg·cm-3.The equilibrium adsorption capacity of Pb2+reaches the adsorption process of 124.52 mg·g-1.3.Compared with cellulose,chitosan containing amino group is more conducive to the in-situ growth of MOF,but it is not as stable as cellulose under solvothermal conditions.HKUST-1 is a typical MOF compound with pore cage structure and has excellent adsorption properties for methylene blue.It is of great significance to prepare aerogels with abundant nucleation sites and stable aerogels which can be used for solvothermal in-situ growth of MOF.For this reason,cotton fiber and chitosan were dissolved in alkaline water system,and epichlorohydrin（ECH）was used as cross-linking agent to prepare covalent cross-linked cellulose/chitosan integral hydrogel（CCSH）,at room temperature for the first time.3D macroporous cellulose/chitosan integral aerogel（CCSA）was obtained by freeze-vacuum drying.Then,3D multiporous HKUST-1/cellulose/chitosan monolithic aerogels（HKUST-1/CCSA）were prepared in p H≈2 ethanol aqueous solution by solvothermal in-situ growth of HKUST-1.The higher the cellulose content is,the more stable the composite aerogel is;with the increase of chitosan content,the composite aerogel is easy to collapse,and the load of HKUST-1 increases.The equilibrium adsorption capacity of the prepared 3D multi-porous HKUST-1/CCSA for methylene blue is 506.8mg·g-1.4.Superelastic aerogels can be compressed and dehydrated after absorbing pollutants,which is beneficial to the rapid regeneration of adsorbents.ML-101（Cr）is synthesized under extreme hydrothermal conditions of strong acid and high temperature above 200℃,with high specific surface area,acid and alkali resistance and excellent thermal stability.24-diaminophenoxyacetic acid can be adsorbed on a large capacity by electrostatic andπ-πaction.Polyacrylamide（PAM）,a widely used sewage flocculant,is an amino-rich,non-toxic hydrophilic linear polymer,which is the preferred substrate for the preparation of gel.For this reason,using the homogenized chitosan hydrogel with alkali dissolution and epichlorohydrin cross-linking as the first network template,the physical interpenetrating double-network polyacrylamide/chitosan integral hydrogel（PAM/CSH）was prepared by in-situ polymerization of monomer acrylamide and crosslinking of N-methylene bisacrylamide（Nmai-N-methylene bisacrylamide）.3D macroporous polyacrylamide/chito-san integral aerogel（PAMCSA）was obtained by freeze-vacuum drying.In addition,MIL-101（Cr）polyacrylamide/chitosan monolithic hydrogel（MIL-101（Cr）PAM/CSH）and3D multiporous MIL-101（Cr）polyacrylamide/chitosan monolithic aerogel（MIL-101（Cr）/PAM/CSA）were prepared by blending appropriate amount of MIL-101（Cr）,during in-situ polymerization.In PAM/CSA,when the mass ratio of acrylamide to chitosan is 6:4,the composite aerogel shows flexibility,but it can not be recovered after compression.After immersion in water,PAM/CSA has no swelling phenomenon and can be easily compressed,and can be quickly restored to the initial state after removing the external force.After blending 30%MIL-101（Cr）in PAM/CSA,the specific surface area increased from 58.15m2·g-1 to 310.94 m2·g-1,which showed a certain degree of compressibility and resilience.MIL-101（Cr）/PAM/CSA can be easily compressed after immersion,and can be quickly restored to the initial state after removing the external force,showing good underwater superelastic characteristics.The equilibrium adsorption capacity of the prepared 3D multi-porous MIL-101（Cr）PAM/CSA for 2-dichlorophenoxyacetic acid is 302.45 mg·g-1. |
