Design,Synthesis And Properties Of Typical Porous Polymers Based Composite Materials

Porous organic polymers?POPs?materials are composed of inorganic,organic and other moieties connected by covalent bonds to form periodic open reticula porous materials.Because of its unique porous structure and multi-purpose skeleton compositions?inorganic-organic and purely organic components?,which has a great research value and wide application prosepects.Nanoentities?NEs?,which are entities with at least one nanoscale dimension,exhibit unique physical and chemical properties that differ from those of their bulk counterparts.Over the last two decades,significant advances in nanoscience and nanotechnology have enabled the rational synthesis of NEs with tunable sizes,compositions,and shapes.This success promises for use in fields such as catalysis,optics,electronics,and magnetic materials.Controllable integration of POPs and functional nanoentities materials is leading to the creation of new multifunctional composites/hybrids,which exhibit new properties that are superior to those of the individual components through the collective behavior of the functional units.In this paper,different functional nanoparticles and different porous organic polymer compounds were combined to prepare a series of new multifunctional materials and their properties in the process of catalysis and sensing were studied.It is very interesting and also a big challenge for encapsulation of metal clusters within microporous solids to expand the application diversity.For this target,herein,we presented an electrochemical synthesis strategy for the encapsulation of noble metals?Au,Pd,Pt?within ZIF-8 cavities.In this method,metal precursors of AuCl₄^-,PtCl₆^2-,and PdCl₄^2-were introduced in ZIF-8 crystals during the concurrent crystallization of ZIF-8 at the anode.As a consequence,very small metal clusters with sizes around 1.2 nm were obtained within ZIF-8 crystals after hydrogen reduction;and these clusters exhibit highly thermal stability,evidenced by the good maintenance of their original sizes after a high-temperature test.The catalytic properties of the encapsulated metal clusters within ZIF-8 were evaluated for CO oxidations.Because of the small pore window of ZIF-8?0.34 nm?and the confinement effect of small pores,about 80%metal clusters?fractions of 0.74,0.77,and 0.75 for Au,Pt,and Pd in ZIF-8 respectively?retained their catalytic activities after exposure to the organosulfur poison of thiophene?0.46 nm?,which was in contrast to their counterparts?fractions of 0.22,0.25,and 0.20 for Au,Pt,and Pd on the SiO₂ support?.The excellent performance of metal clusters encapsulated within ZIF-8 crystals would bring new opportunities for catalytic reactions.Gas sensing performances are critically limited by fast electron-hole recombination,low gas selectivity and elevated operation temperature in ZnO sensors.To alleviate these problems,new and high-performance sensor materials are desirable.Herein,we fabricated a core-shell composite material of POM@ZIF-8@ZnO with ultrathin ZIF-8film containing H₅PMo₁₀V₂O₄₀ polyoxometalate on the ZnO substrate surface.The device based on this composite exhibited improved gas sensing ability toward formaldehyde?HCHO?at room temperature?25°C?with a sensitivity of⁰.4 ppm.Additionally,the POM@ZIF-8@ZnO material exhibited selective gas response for reducing gases with small molecular sizes,in particular for the selectivity ratio of 15.0for formaldehyde over ethanol.The specific roles of ZIF-8 shell and POM were discussed in detail:ZIF-8 was responsible for concentrating and recognizing analyte molecules on the ZnO surface,and POM accounted for enhancing sensing ability.The new material of POM@ZIF-8@ZnO with high performance held great promise in sensor materials for selective formaldehyde sensing.In the oxidative desulfurization processes with hydrogen peroxide as an oxidant,polyoxometalates?POMs?catalysts cannot contact the organic sulphur compounds in the oil phase efficiently due to their hydrophilic property,and the reaction rates are hardly desirable.The porous organic framework materials have high porosity and specific surface area with elevated thermal stability.Among them,porous aromatic skeleton material PAF-1 is the one with excellent properties,which has carbon rigid skeleton with hydrophobic properties,diamond topology,superior high specific surface area,thermal and hydrothermal stability.Therefore,the POM-PAF-1composite material catalyst to be formed by chemical bonding of POM molecules on PAF-1 was designed,which could made full contact between POM and organic sulfides by using the hydrophobic hydrophilicity of PAF-1substrate.The catalytic properties of POM-PAF-1 on desulfurization were carried out with simulated oil?composed of n-octane and dibenzothiophene?in hydrogen peroxide/acetonitrile system.It was found that the hydrophobicity of PAF-1 subtract could astrict the hybrid POM functional units exposed both of the oxidant and reactant sufficiently,and decreased the activity energy obviously.The rate of the catalytic reaction was increased.On the other hand,the rigid aromatic skeleton of PAF-1 bonded POMs through covalent bond which prevented POMs units from leaching out or agglomeration during violent react conditions ensured the stability of recycle utilization of the catalytic materials.The excellent performance of this new composite material would bring new opportunities for oxidative desulfurization technology.