贵金属负载的MOFs材料的制备及其光催化性能研究

【作者】 赵敏；

【导师】 崔世海； 陈森；

【作者基本信息】 南京师范大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 近年来,新兴污染物的滥用和不当排放对水体或人类健康构成风险。因此,有效简便绿色的光催化技术逐渐成为了去除水环境中污染物的热点方法。其中,贵金属纳米颗粒（NMNPs）由于具有较高的表面体积比,能提供大量可用的活性位点;良好的催化活性;优良的选择性和可回收性;特有的表面等离子体共振效应,可拓宽光吸收范围和强度;可作为载流子分离中心等特点引起了广泛关注。然而,由于其价格昂贵、易聚集和不稳定性等因素,通常可将其负载至多孔材料金属-有机框架（MOFs）上以制备复合催化剂。本论文以NMNPs@MOFs这类复合催化剂为基础,利用双金属合金和上转换材料等制备系列的复合光催化复合材料,并选择部分新兴污染物为研究对象评估其催化活性。通过质构特性和光电特性详细研究了NMNPs@MOFs基复合材料的结构-活性关系;结合总有机碳测试、三维荧光、液-质联用技术并基于密度泛函理论（DFT）计算分析目标污染物降解过程中的中间产物和降解路径,为后续高效NMNPs@MOFs型催化剂的设计提供新思路。1、通过溶剂热法合成PtCu/MIL-101（Cr）复合材料并应用于BPA的光催化降解。材料的系列表征证明PtCu金属簇处于合金化状态,PtCu合金所拥有的光热协同催化为催化体系注入了高密度光子和热通量,PtCu/MIL-101（Cr）复合催化剂在100 min内对BPA的降解率可达99.65%。同时,采用液-质联用、总有机碳测试和三维荧光等对BPA的降解路径和中间产物进行了分析,并揭示降解机理。2、采用多步合成法制备ZIF-67/Ag NPs/NaYF₄:Yb,Er三元复合催化剂,并将其用于去除水环境中的SDZ。UV-vis DRS显示ZIF-67/Ag NPs主要吸收紫外和可见光,而NaYF₄:Yb,Er在近红外光的激发下可发射可见光中的红绿蓝光,且能被ZIF-67/Ag NPs吸收。通过系列光电表征探究了光生e^--h⁺对的分离和转移,并结合捕获实验阐明了降解过程中起主要作用的活性物种。3、使用乙二醇还原制备PtNPs并将其分别负载于MIL-53（Al、Cr、Fe）以合成系列Pt/MIL-53复合催化剂。利用电镜、XPS、水接触角等表征材料的形貌、结构与组成。以KP为目标污染物,通过质构关系和光电特性比较分析NMNPs@MOFs催化体系的不同,以揭示Pt/MIL-53催化降解性能的差异,此外,利用液-质联用和DFT计算分析KP降解过程中的中间产物与降解路径,并推断可能的光催化机理。更多还原

【Abstract】 In recent years,the misuse and improper discharge of emerging pollutants have posed a risk to water bodies or human health.Therefore,effective,simple and green photocatalytic technology is emerging as a hot method for removing pollutants from the aqueous environment.Among them,noble metal nanoparticles（NMNPs）have attracted much attention due to their high surface-to-volume ratio,which provides a large number of active sites;good catalytic activity;excellent selectivity and recoverability;unique localised surface plasmon resonanceeffect,which broadens the range and intensity of light absorption;and the ability to act as a carrier separation center.However,due to their high price,easy aggregation and instability,they can usually be loaded onto porous metal-organic frameworks（MOFs）to prepare composite catalysts.In this thesis,a series of composite photocatalytic composites based on NMNPs@MOFs were prepared using bimetallic alloys and upconversion materials,and some emerging pollutants were selected to evaluate their catalytic activity.The structure-activity relationships of the NMNPs@MOFs-based composites were investigated in detail by texture properties and optoelectronic properties,and the intermediates and degradation pathways in the degradation of the target pollutants were analyzed by combining total organic carbon testing,3D fluorescence,liquid-mass coupling techniques and density flooding theory（DFT）calculations.It provides new ideas for the design of subsequent high-efficiency NMNPs@MOFs-type catalysts.1.PtCu/MIL-101（Cr）composites were synthesized by a solvothermal method and applied to the photocatalytic degradation of BPA.The series characterisation of the material demonstrated that the PtCu metal clusters were in an alloyed state and the photothermal synergistic catalysis possessed by the PtCu alloy injected high density photons and heat flux into the catalytic system,and the PtCu/MIL-101（Cr）composite catalyst achieved 99.65%degradation of BPA within 100 min.Meanwhile,the degradation pathways and intermediates of BPA were analyzed using liquid-mass coupling,total organic carbon testing and three-dimensional fluorescence,and the possible degradation mechanism was revealed.2.ZIF-67/Ag NPs/NaYF₄:Yb,Er ternary composite catalysts were prepared by a multi-step synthesis method and used for the removal of SDZ in aqueous environment.UV-vis DRS shows that ZIF-67/Ag NPs mainly absorb ultraviolet and visible light.At the same time,NaYF₄:Yb,Er can emit red,green and blue light in visible light under the excitation of near infrared light,and can be absorbed by ZIF-67/Ag NPs.The separation and transfer of photogenerated e^--h⁺pairs were investigated by a series of photoelectric characterization,and the active species whose main role in the degradation process was elucidated in combination with capture experiments.3.PtNPs were prepared using ethylene glycol reduction and loaded onto MIL-53（Al,Cr,Fe）respectively to synthesize a series of Pt/MIL-53 composite catalysts.The morphology,structure and composition of the materials were characterized using electron microscopy,XPS and water contact angle.Using KP as the target pollutant,the differences in the catalytic systems of NMNPs@MOFs were analyzed by comparative texture properties and photoelectric properties to reveal the differences in the catalytic degradation performance of Pt/MIL-53.In addition,LC-MS and DFT calculations were used to analyze the intermediates and degradation pathways during the degradation of KP and to deduce the possible photocatalytic mechanism.1.PtCu/MIL-101（Cr）composites were synthesized by the solvothermal method,and the catalytic activity was investigated by degrading BPA.The PtCu metal clusters were demonstrated to be in an alloyed state by a series of characterizations.Within100 minutes,PtCu/MIL-101（Cr）was able to degrade 99.65%of BPA.This is due to the photothermal co-catalysis possessed by the PtCu alloy,which can inject a high density of photons and heat flux into the catalytic system.The results of the photothermal co-catalysis experiments were carefully compared and analyzed with those of photocatalysis and thermal catalysis.The degradation pathways and intermediates of BPA were analyzed by LC-MS and calculated based on density flooding theory.2.In this paper,ZIF-67/Ag NPs/NaYF₄:Yb,Er ternary composite catalysts were synthesized by a multi-step synthesis method and used for the removal of SDZ in aqueous environment.UV-vis DRS demonstrated that ZIF-67/Ag NPs mainly absorbed UV and visible light,while NaYF₄:Yb,Er could be excited by near-infrared light.Under an external excitation source at 980 nm,NaYF₄:Yb,Er emits mainly red,green and blue light in the visible range.This indicates that the ZIF-67/Ag NPs absorb the light released by NaYF₄:Yb,Er.The separation and transfer of photogenerated e^--h⁺pairs were explored by a series of photoelectric characterization.The active substances generated during the degradation process were obtained by capture experiments.Combined with the above results,the photodegradation mechanism of this ternary composite system was investigated in depth.3.PtNPs obtained from the reduction of ethylene glycol were loaded onto MIL-53（Al、Cr、Fe）to obtain Pt/MIL-53 composite catalysts,respectively.The morphology,structural properties and composition of the materials were compared and studied through extensive characterization.The catalytic effect of Pt/MIL-53 on the degradation of KP by simulated solar irradiation varied considerably,with the order of activity being Pt/MIL-53（Al）>Pt/MIL-53（Cr）>Pt/MIL-53（Fe）.The factors influencing the differences in activity were carefully compared through structure-activity relationships,in other words the catalytic activity of the NMNPs@MOFs catalytic system was analyzed comparatively through the qualitative and optoelectronic properties.Furthermore,the intermediates and degradation pathways of Pt/MIL-53（Al）（the best catalytic activity）for the degradation of KP were further examined using LC-MS and DFT calculations.Furthermore,deduced from the photoelectron characterization was a potential photocatalytic mechanism.更多还原