Synthesis,Characterization Of Three-Dimensional Porous Nanocomposites And Their Application In Catalysis And Water Remediation

Three-dimensional porous nanocomposites?3D PNCs?,as a new material system,have broad research space and application prospect in biomedical engineering,adsorption,environmental remediation,optoelectronic devices,energy storage and catalysis,etc.because of their large specific surface area,rich pore structure,high mass transfer and low density.Easy aggregation of low dimensioal nanomaterials,such as zero-,one-,and two-dimensional nanomaterials,results in the decrease of active sites and specific surface area,thus weakening the performance in application.Therefore,the construction of 3D PNCs based on low dimensional building blocks can not only maximumly retain the active sites of each components,but also create additional hierarchical porous structures.Structural stability is the precondition of the hierarchical porous structures in 3D PNCs,which directly affects the robust application.We built structure-stable 3D PNCs by the formation of covalent bonds and the support of 2D nanomaterials based on the above research background.Finally,we focused on catalysis and water remediation of these novel materials.The contents of this paper are summarized as follow in six chapters:In the first chapter,we summarized the preparation,properties and application of3D PNCs based on graphene,molybdenum disulfied,and carbon nitride 2D unit components.In addition,the development in the catalysis of Tsuji-Trost reaction and arylation reaction was described.In the second chapter,three-dimensional framework palladium-reduced graphene oxide?Pd-rGO?was constructed and used for selective catalysis in Tsuji-Trost reaction.We developed a method to construct novel 3D graphene framworks with hierarchical pores by covalention.Triethylene tetramine?TETA?chains were used as linkers to covalently connect with carboxylated graphene oxide?GO-COOH?to form3D graphene oxide framworks?GOF?.The residual N atoms coordinated with the in-situ generated Pd NPs.The final 3D Pd-rGOF has hierarchical pores in macro-and meso-size.The covalence between TETA chains and GO-COOH ensured the stability of GOF,and created numerous pores meanwhile.Pd NPs were embeded in rGOF,reducing the exposion,which ensured the structure stability of Pd NPs.Additionally,the coordination by N atoms prevented the leaching and aggregation of Pd NPs.Pd-rGOF showed superior catalytic activity and selectivety for Tsuji-Trost reaction in air and water system.The hierarchical pores can be acted as nanoreactor,effectively promoting the surface contact between substrates and Pd NPs.The formed 3D GOF template can be also used to load other noble metal nanoparticles for catalysis.In the third chapter,molybdenum disulfide conjugated polypyrrole frameworks supported Pd nanoparticles?Pd@MoS₂CPFs?was constructed and used for synergistic photocatalysis in Tsuji-Trost reaction.We constructed robust 3D Pd@MoS₂CPFs by ultrasound mediated one-step redox/complexation process,in which Pd NPs and PPy layer were inserted between the layers of Mo S₂ by palladium salts reduction and pyrrole polymerization,respectively.In such process,porous 3D frameworks were constructed by forming amidate between the carboxyl groups on the MoS₂ NSs and amido of PPy,as well as the coordination between molybdenum atoms in MoS₂ and nitrogen atoms in PPy.In-situ generated Pd NPs were evenly located in MoS₂CPFs,forming effective Mott-Schottky junction with MoS₂ NSs and PPy.Pd@MoS₂CPFs have enhanced absorption in UV-vis-NIR whole light range,and better electron/hole pairs seperation with the help of electron transfer promotion of Pd NPs.In addition,3D hierarchical porous structures provide effective mass transfer.The nanohybrids have a well-defined 3D morphology,confined metal NPs,high surface area,and enhanced optical absorption capacity,promising candidates as visible light photocatalysts.With these merits,Pd@MoS₂CPFs exhibited unexpected photocatalytic activity and robust cycling for the direct Tsuji-Trost reaction between allylalcohol and 1,3-dicarbonyl under visible light at room temperature.This procedure can be used to build other metal nanoparticles@MoS₂CPFs.In the fourth chapter,aligned carbon nitride-polypyrrole heterojuction aerogel with tunable energy gap was constructured and used as an efficient vis-NIR light driven photocatalyst.We demonstrated that aligned heterojuction aerogel can be assembled by directional freezing of polypyrrole?PPy?/polyvinyl alcohol?PVA?composites and C₃N₄ NSs.The resultant heterojunction aerogel?denote as CNPVPy?has long-range channel aligned structures along the whole monolithic sample,enabling mass transport and efficiently contact between the reaction substrates and catalysts.The active species PPy and C₃N₄ NSs formed p-n heterojunction,in which electron will transfer from PPy to the coonduction band of C₃N₄ NSs,promoting charge seperation.The energy gap of CNPVPy can be tuned by changing the ratio of PPy and C₃N₄ NSs.We demonstrated that CNPVPy macrosturctures are highly efficient under visible-NIR light for the direct arylation of heteroaromatics at 25 ^oC.Interestingly,CNPVPy heterojuction aerogel exhibits high photocatalytic activity,far exceeding those of the single-and mixed-component systems.Furthermore,this photocatalyst is very stable in repeated cycling.This finding constituted the first experimental evidence of the photocatalytic activity of aligned metal-free heterojuction aerogel under visible-NIR light for synthesis of fine chemicals.In the fifth chapter,hyper-cross-linked porous molybdenum disulfide-cyclodextrin polymer frameworks?MoS₂CDPFs?were constructed and used for rapid and durable removal of aromatic phenolic micropollutant from water.Aminated-CD-modified MoS₂ NSs were used as structural motifs for the construction of MoS₂CDPFs,and CD polymer was uniformly incorporated.Besides the pores created between MoS₂ NSs,the introduction of CDP produces extra gaps between MoS₂ NS_S and CD.With these merits,we used MoS₂CDPFs as enhanced adsorbents to remove BPA from water.Their rapid sequestration of micropollutant BPA?0.1 mM?from water combined with the highest removal efficiency far exceeded those of the single-and two-component hybrids.The intercalation between MoS₂ NSs with CD polymer imparts the frameworks durability in adsorption/desorption of aromatic phenolic micropollutants.This is the first example to integrate MoS₂ NSs and CD as a promising adsorbent for aromatic phenolic micropollutant removal from aqueous system.In the sixth chapter,we summrized the above four works,and prospected the following works.