Preparation And Properties Of Supramolecular Gels Based On Self-assembly Of Small Molecules

Supramolecular gel is a three-dimensional cross-linked network structure containing a large number of solvents formed by reversible secondary interactions.Compared with polymer gels,supramolecular gels,as one of the most attractive soft materials,have excellent stimulus response,but also have more flexibility in regulation.They can easily adjust the proportion,concentration and environmental conditions to achieve the regulation of performance.In this paper,supramolecular hydrogels were prepared by 3,5-dihydroxybenzoic acid,isonicotinic acid and xanthine,and the gelation mechanism and microstructure were investigated by FTIR,XRD,SEM and other test methods.In addition,the basic properties of the gel and the influence of the external environment（temperature,pH,ions,solvents,etc.）on the gel were also studied.Based on the properties of supramolecular gel,the potential of its functional application in the field of adsorption was further explored.The main contents are as follows:（1）3,5-dihydroxybenzoic acid（D）and isotinoid（I）form white two-component supramolecular hydrogels in water at a molar ratio of 2:1.The microstructure of the dry gels was characterized by the interlinked fibrous rod structure.Hydrogen bonding was the main driving force of gel formation,andπ-π.The Hansen solubility parameter provided a method to clearly distinguish the gelation behavior of two components in different mixed solvents.When the hydrogen bond valueδ_h=35.8～42.3,the gelation can be formed.The gel was temperature and pH sensitive gel with reversibility to both temperature and pH.Meanwhile,the DI gel had fast response to F^-and Fe³⁺,which was expected to be applied in the field of visual ion recognition.（2）Xanthine could coordinate with copper ions to form Cu（Ⅱ）supramolecular metal gel（Cu-MOG）with the aid of triethylamine.The gel showed certain stimulus response to mechanical action,EDTA and Na₂S,and had great resistance to heat,acid and alkali.Based on the porous and charge characteristics of the gel,the Cu（Ⅱ）-based supramolecular metal gel could effectively adsorb the cationic dye methylene blue,the adsorption rate is more than 99%,the maximum adsorption capacity is more than 120 mg/g,and the adsorption equilibrium is basically achieved within 30min.This work shows the possibility for the application of Cu-MOG xerogel in the field of dye wastewater treatment and provides new information for the further development of supramolecular hydrogels as adsorbents.（3）An alumina hydrogel based on coordination was prepared using Aluminum chloride hexahydrate and urea as raw materials.MgO/Al₂O₃aerogel with high specific surface area was obtained by introducing Mg²⁺into the system and drying with supercritical fluid.The aerogel was a porous structure constructed by nanoparticles and nanosheets,with high specific surface area and rich multi-layer pore structure.Magnesium oxide was highly dispersed on the alumina carrier.The excellent physical and chemical structure provided a theoretical basis for efficient carbon dioxide adsorption.MgO/Al₂O₃aerogel samples showed excellent CO₂adsorption performance,reaching 23.49 wt%and 20.89 wt%at（300℃,CO₂flow rate:50 m L/min）.This material is expected to be applied in the field of carbon dioxide capture.