| With the rapid development of modern economic level and the improvement of the life quality of people around the world,the depletion of non-renewable resources and the destruction and pollution of the ecological environment have become major and serious problems restricting the development of human society.In particular,serious water resource shortage and water pollution have attracted more and more attention.Photocatalytic materials can effectively degrade and purify aromatic organic pollutants,organic dyes,and pathogenic microorganisms in the environment,and the photocatalytic technology could be a promising approach for water treatment.However,the current photocatalytic technology still suffers from some key issues that limit its real application for water treatment,including low utilization rate of sunlight energy as the photon energy,high recombination probability of photo-generated electron-hole pairs during their separation and transportation,and weak adsorption capacity of organic pollutants.Unlike traditional inorganic photocatalysts,organic semiconductorbased photocatalysts are generally composed of non-metallic elements.Their raw materials are abundant and their synthesis conditions are generally mild.Moreover,their monomer molecule structures could be designed as needed,which is beneficial for their electronic structure modulations to develop more effective photocatalytic material systems and broaden their applications in different types of photocatalytic reactions.So,the synthesis and photocatalytic water treatment properties of polymers with conjugatedπ bonds were explored in this work.The specific research contents and conclusions are as follows:First,an easy-to-operate,simple,and efficient solution polymerization method was adopted to synthesize the polyacrylonitrile(PAN)photocatalyst with a twodimensional planar structure.Polyacrylonitrile,a low-cost homopolymer mainly used in the textile industry,was found to have photocatalytic capabilities due to its good light absorption and suitable band structure capable of generating free radicals.Under simulated solar irradiation,it effectively degraded organic pollutants such as phenol and sulfamethoxazole(SMX),and kills Escherichia coli(E.coli)bacterium.After 2 h of light exposure,the remaining concentrations of phenol and SMX in the solution decreased to～75.9%and 89%,respectively,while the survival rate of E.coli dropped to～28%after 1 h of simulated solar exposure.In the photocatalytic process,h+and·O2were identified as the main active species.The planar PAN structure also exhibited good stability and reusability,as well as good photocatalytic performance in the real aqueous matrix of tap water,which is beneficial for its practical application.Therefore,PAN and PAN-based polymers can become a series of novel organic semiconductor photocatalytic materials for applications in various technologies,especially as wearable products with self-disinfection function to prevent bacterial and viral infections.Secondly,a two-dimensional conjugated polyacrylonitrile photocatalytic material with conjugated large π bonds was prepared for the first time using polyacrylonitrile as the synthetic raw material.In the conjugated polyacrylonitrile,the conjugated structural unit was composed of carbon and nitrogen in the form of linear and planar configurations.In particular,the nitrogen atom was involved in the conjugated system of the entire molecule.Thus,a large conjugated π bond was formed,which resulted in a better absorption of visible light,easier photogenerated charge carrier separation and faster migration,and subsequently an improved photocatalytic activity.Under visible light irradiation,conjugated polyacrylonitrile(CP AN)exhibited superior photocatalytic degradations of organic pollutants of phenol and tetracycline(TC),and enhanced photocatalytic disinfection of Escherichia coli bacterium,compared with PAN without cyclodehydrogenation.After five cycles of experiments,CP AN showed a good stability and recyclability.Its photocatalytic degradation performance was also good in the real water matrix of tap water,demonstrating its great potential for water purification in various natural environments.Thirdly,sulfur-containing conjugated polymers,S-CP and SS-CP,were prepared by utilizing a simple polymerization reaction.In this case,the introduction of heteroatoms and their planar structures combined to provide the capability to adjust theπ bond delocalization degree of these conjugated polymers.Their greater π bond delocalization degrees could alter their energy band structures,strengthen their visible light absorption,promote the separation of photogenerated charges,and enhance their adsorption of organic pollutants,all of which were beneficial to enhance their photocatalytic activities.With a higher degree of conjugation,SS-CP photocatalytic material demonstrated a better visible light absorption capability and a higher photogenerated electron-hole transfer efficiency than S-CP photocatalytic material.However,the specific surface area of S-CP photocatalytic material was 2.4 times larger than that of SS-CP photocatalytic material,which provided it a better ability to adsorb organic pollutants.Thus,S-CP photocatalytic material demonstrated a better photocatalytic degradation effect than that of SS-CP photocatalytic material as shown in their photocatalytic degradations of rhodamine B(RhB)and tetracycline(TC)under visible light irradiation.In the photocatalytic degradation process,·O2-was found to be its active species.Photocalytic performances of S-CP and SS-CP polymers demonstrated that the conjugated polymers containing sulfur heteroatoms(S-CP and SS-CP)have broad application potentials for water pollution treatment in the natural environment,especially for organic dye pollutions. |
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