Solvothermal Synthesis Of Nanoporous Polymers And Their Adsorptive Properties

Organic chemical pollutions in air and water are strongly endangering all kinds of lives, and especially human being nowadays. To solve this problem, various porous adsorbents have been developed such as carbons, silicas, organic-inorganic hybrid materials, resins and natural clays. In particular, activated carbon is widely applied due to its high surface area and abundant porosity. However, activated carbon is still not efficient enough because of its finite pore volume and its adsorption on water. When a chemical accident occurs, activated carbon has a difficulty in controlling the pollution even if used in a large amount. Recently, lipophilic polyelectrolyte gels are successfully developed for adsorption of nonpolar organic solvents, and these polyelectrolytes can swell in some nonpolar organic solvents up to hundreds of times their dry size. However, they are not intrinsic porous materials, which results in their disability for gas adsorption. In addition, the low crosslinking density of these polyelectrolytes exhibits swelling property only towards nonpolar solvents. Commercial porous resins are widely used as adsorbents for organic compounds in water and air. Unfortunately, their adsorptive capacity is still low due to their poor swelling property. Furthermore, their poor stability and complex preparative process strongly limit their industrial applications. Therefore, it is still challenging to prepare porous materials with swelling properties as efficient adsorbents that show ultra-high adsorptive capacity, quick adsorptive rates, and high stability. We demonstrate here a design and synthesis of efficient adsorbents for organic compounds. The features of efficient adsorbents are proposed in the following: (i) large and abundant porosity have an advantage in adsorption and mass transfer, leading to fast adsorption; (ii) swelling property is favorable for increasing adsorptive capacity; (iii) general applicability to all kinds of organic compounds and selectivity against water adsorption are helpful for the removal of pollutants in the environments; (iv) reusability is also very important for the practical applications. Accordingly, through a novel solvothermal route, we have successfully synthesized a series of nanoporous polydivinylbenzene (PDVB) with abundant porosity and swelling properties for the first time in the presence of solvents such as tetrahydrofuran (THF) that act as'template'for the formation of porosity. The resultant samples show very large surface areas (550-700 m2/g), adjustable pore sizes (3.9~22.0 nm), superhydrophobicity, superoleophilicity and rapid swelling properties. Notably, such swelling mesoporous polymers exhibit ultra-high adsorptive capacity and rapid adsorptive rates for a series of organic compounds and could be regenerated easily. All of these unique features would result in their superior adsorptive properties and attractive applications to cleaning organic pollution in water and air.Differing from inorganic porous materials which could be regenerated by simple calcinations, porous polymeric and carbon materials could be reused again only after using a proper method to desorb the adsorbed pollutants, hence strongly impeding their industrial applications. An ideal adsorbent would decompose pollutants and self-regenerate for recycling use. On the other hand, photocatalytic degradation of organic pollutants is also a fascinating choice to solve environmental problems. However, the low frequency of collision between photocatalysts and organic pollutants lower the reaction rate of mineralization. Furthermore, secondary pollution caused by byproduct during the photocatalytic process also limits the practical applications of photocatalysts. In addtion, such heterogeneous photocatalysis process was usually carried out using suspension of fine titania powder (e.g. P25 10~50 nm particles of TiO2), and the separation and recovery of the slurries are considerably difficult for large scale applications. Thus, this matter strongly limits the practical use of photocatalysts in environmental protection. Therefore, a promising way to overcome the above disadvantages is to combine the advantages of adsorbents and photocatalysts in a controlled fashion. From the practical point of view, attempts have been made to immobilize photocatalysts on various adsorptive supports, e.g., loading TiO2 particles onto various adsorbents (activated carbon, zeolite, Al2O3, mesoporous silicate, and natural clay), synthesis of mesoporous titania, fabrication of mesoporous TiO2/SiO2, TiO2/C composites. The as-obtained materials reveal improved property for both adsorption and photodegradation of organic pollutants. However, an evaluation of superior adsorptive property of these multifunctional materials is still in lack. In addition, immobilization of commercial P25 particles onto porous supports is difficult to perform, and mechanical mixture of the two materials works less efficiently. Thus, it is still a challenge to develop highly efficient adsorptive materials along with excellent photocatalytic activity to realize a promising and elegant synergism between adsorbents and photocatalysts.Herein, we demonstrate for the first time a novel in-situ synthesis of titania nanocrystals and nanoporous polymers nanocomposites as efficient multifunctional materials for both adsorption and photocatalytic degradation. Crystalline titania nanoparticles (5-10 nm) distribute homogeneously in the matrix of adsorptive polymers. Nanoporous polymer framework exhibits a hierarchical porous structure in mesopore and macropore range. The nanocomposites reveal high BET surface area (354-651 m2/g), high thermal stability (higher than 370°C) and high stability under UV irradiation. In particular, these composite materials exhibit both superior adsorptive property and high photocatalytic activity. We also present an in-situ synthesis of nanoporous polymers as adsorptive supports for P25 photocatalyst for the first time. The resultant composites reveal monolith morphology with nanoporous structure and high surface area. The composites also exhibit both superior adsorptive property and high photocatalytic activity. Thus, these multifunctional materials would have a promising potential used in decontamination of organic pollutants in air and water.Additionally, waste water usually contains various pollutants, such as dye molecules, oil, heavy metal ions and so on. Thus, there is an urgent call for preparation of multifunctional adsorbents for treating all kinds of pollutants in waste water. In this work, we introduced methacrylic acid monomers into the preparative system of nanoporous polydivinylbenzene. Finally, carboxyl group functionalized nanoporous polymers had been successfully prepared. The obtained materials were used as multifunctional adsorbents for treating waste water and exhibited superior adsorptive properties for a serious of pollutants.