【作者】 张新；

【导师】 钱国栋；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2019， 博士

【摘要】 金属-有机框架（Metal-Organic Frameworks,MOFs）材料是由有机配体和金属离子通过配位键自组装而成的一类有机-无机杂化材料。随着MOFs的发展,通过后功能化修饰将各种官能团引入到MOFs中以及将MOFs与其它各种材料进行复合增加其功能性的需求明显增加。目前,发光MOFs由于其在化学传感和发光器件中巨大的应用前景而备受关注。MOFs在荧光传感方面有其固有的优势,它们可以有效地将待测物分子富集到较高的浓度以增强主-客体间的相互作用从而输出响应信号。在本文中,针对待检测的目标物(Hg²⁺、H⁺和H₂S),采用后功能化修饰的方法,在水稳性MOFs中引入特定的识别基团,开发了一系列基于MOFs的具有低检测限、高选择性和快速响应的荧光传感材料。本文还结合MOFs和聚合物两者的优势制备混合基质膜材料,将该材料用于硫化氢检测。以2-叠氮-1,4-对苯二甲酸（H₂BDC-N₃）为有机配体,采用溶剂热法合成了纳米尺寸锆基MOF材料UiO-66-N₃。采用后功能化修饰的方法,在一价铜催化作用下,使UiO-66-N₃的叠氮基团与苯乙炔的炔基发生环化加成反应（CuAAC）,制备了一种新型MOF荧光探针UiO-66-PSM。该探针与Hg²⁺的荧光响应比其他金属离子更为明显,通过探究表明点击反应生成的三氮唑部分可以作为Hg²⁺的结合位点。该探针具有快速响应（响应时间小于15 s）、优异的选择性和低检测限（检测限:5.88 μM）等特点。此外,它能够准确检测出实际水样中加入的Hg²⁺浓度,显示出很大的实际应用潜力。为了解决UiO-66-PSM传感材料仅依靠配体发光来检测目标物,且配体发光比较弱的科学问题,以2,2’-联吡啶-5,5’-二羧酸（H₂bpydc）作为有机配体,采用溶剂热法合成了纳米尺寸锆基MOF材料UiO-67-bpydc。进而通过后功能化修饰的方法,在UiO-67-bpydc桥联配体不饱和氮位点上配位Eu³⁺离子来制备荧光传感材料Eu³⁺@UiO-67-bpydc。由于配体对Eu³⁺的敏化作用,Eu³⁺@UiO-67-bpydc具有优异的发光性能,且其发光性能显示出很强的pH依赖特性。Eu³⁺@UiO-67-bpydc在pH为1.06至10.99的酸碱溶液中均具有良好的稳定性,这使其在宽范围pH传感应用方面具有极大的潜力。此外,该传感材料具有优异的循环使用性能和生物相容性。Eu³⁺@UiO-67-bpydc在PC 12细胞中的荧光成像实验表明其具有应用于体内检测的潜力。鉴于其出色的稳定性和荧光强度随pH变化的特性,该荧光探针在体外和体内pH检测方面都具有很大的应用潜力。Eu³⁺@UiO-67-bpydc依靠单峰强度检测目标物,而单峰强度易受外界干扰。为此,以1,2,4,5-均苯四甲酸（H₄btec）为有机配体,采用水热法合成了纳米尺寸结基MOF材料UiO-66-（COOH）₂。利用Eu³⁺和Cu²⁺离子对UiO-66-（COOH）₂进行改性,Eu³⁺/Cu²⁺@UiO-66-（COOH）₂同时显示出Eu³⁺尖锐的特征发射峰和较宽的配体中心发射。Cu²⁺离子的存在会抑制Eu³⁺的发光,加入H₂S之后,由于S^2-与Cu²⁺离子之间具有极强的亲和力而生成CuS,使得Eu³⁺的荧光增强,配体中心发光猝灭,从而使Eu³⁺/Cu²⁺@UiO-66-（COOH）₂展现出低检测限（检测限:5.45uM）、高选择性和快速的H₂S传感响应（响应时间小于30 s）。此外,这种用于H₂S传感的方法有望应用到其它含有未配位-COOH的水稳性MOFs。鉴于Cu²⁺与桥联配体裸露羧基配位之后Eu³⁺/Cu²⁺@UiO-66-（COOH）₂整体发光强度比较弱,利用Eu³⁺和Ag⁺离子对MOF UiO-66-（COOH）₂进行改性,进而构筑Eu³⁺/Ag⁺@UiO-66-（COOH）₂用于检测哮喘病生物标记物H₂S的逻辑平台。这种基于Eu³⁺@UiO-66-（COOH）₂的INHIBIT逻辑门,选择Ag⁺和H₂S作为输入,选择615nm处的荧光信号（1615）作为输出。荧光研究结果表明,Eu³⁺/Ag⁺@UiO-66-（COOH）₂具有响应快（响应时间小于30s）、选择性强、低检测限（检测限:23.53μM）以及能实现H₂S的实时原位检测等优点。此外,细胞实验表明Eu³⁺/Ag⁺@UiO-66-（COOH）₂具有良好的生物相容性,在稀释的血清样品中准确检测出加入的H₂S含量,表明其适用于体内生物标志物H₂S的检测。针对粉体MOFs用作荧光传感材料检测限较高的科学问题,以2-硝基对苯二甲酸（H₂BDC-NO₂）为有机配体,采用溶剂热法合成了纳米尺寸铝基MOF材料Al-MIL-53-NO₂。通过将具有高度稳定性的Al-MIL-53-NO₂与聚偏氟乙烯（PVDF）混合,制备了 MOF基混合基质膜（Mixed-Matrix Membranes,MMMs）。与纯MOF膜的固有脆性和较差的可加工性不同,MOF基MMMs表现出较为理想的柔性和可加工性能,更有利于该传感材料的实际应用。由于Al-MIL-53-NO₂颗粒的均匀分布和MOFs的永久孔隙率,MOF基MMMs显示出良好的水渗透通量,有利于检测过程中分析物和MOFs之间的充分接触。因此,MOF基MMMs传感材料（MOFs的质量百分比占比70%）对H₂S的检测具有高的选择性和低检测限,检测限低至92.31 nM。更多还原

【Abstract】 Metal-organic frameworks（MOFs）,built from metal ions and organic linkers,have evolved as an important class of promising microporous hybrid crystalline materials.Along with the development of MOFs chemistry,the requirement of introducing various functional groups into MOFs and compounding MOFs with other materials has increased significantly.At present,the luminescent MOFs have gathered a great deal of attention due to their potential applications in light-emitting devices and chemical sensors.MOFs have inherent advantages in luminescence sensing because they can effectively concentrate analyte molecules at higher levels to enhance the host-guest interactions to export an analytical response.Herein,for specific targets(Hg²⁺,H⁺,or H₂S)to be detected,specific recognition sites are introduced into water-stable MOFs.We have developed a series of MOF sensors with low detection limit,high selectivity and fast response.In this work,we also combine the advantages of both MOFs and polymers to prepare mixed-matrix membranes（MMMs）for detection of H₂S.Based on 2-azido-1,4-benzenedicarboxlyic acid（H₂BDC-N₃）,a novel MOF fluorescent probe UiO-66-PSM is obtained by the copper-catalyzed azide-alkyne click（CuAAC）reaction of UiO-66-N₃ with phenylacetylene.The click-generated triazole unit can act as the metal binding site to coordinate with Hg²⁺,which exhibits the most pronounced fluorescence response over other metal ions.The probe provides low detection limit(detection limit,5.88（μM）,high selectivity and fast response（response time,15 s）to Hg²⁺.Moreover,it is capable of detecting Hg²⁺ in environmetal water samples without any structural disintegration of the framework,indicating its high potential in practical applications.In order to solve the problem that UiO-66-PSM sensor relies on ligand luminescence to detect target,but the ligand luminescence is weak.By using organic ligand 2,2’-bipyridine-5,5’-dicarboxylic acid（H₂bpydc）,a fluorescent pH sensor based on post-functionalization modified nanoscale UiO-67-bpydc by encapsulating Eu³⁺cations in the pores was fabricated.The Eu³⁺ incorporated sample(Eu³⁺@UiO-67 bpydc shows excellent luminescence due to the sensitization and protection provided by the parented framework.Subsequently,Eu³⁺@UiO-67-bpydc was developed as a pH sensor.Eu³⁺@UiO-67-bpydc shows good chemical resistance to both acidity and alkalinity solutions with pH ranging from 1.06 to 10.99,which makes it potentially useful for wide-range pH sensor.In addition,cycling experiments have demonstrated the utilizability of the sensor.The MTT analysis shows that Eu³⁺@UiO-67-bpydc possesses favourable biocompatibility.Furthermore,fluorescence imaging of Eu³⁺@UiO-67-bpydc in PC 12 cells was also performed to test its feasibility in vivo.Given its exceptional stability and pH-dependent fluorescent intensity,the fluorescent prob e should be a promising candidate for application in fluorescent pH sensing in vitro and in vivo.Eu³⁺@UiO-67-bpydc relies on single peak intensity to detect the target,and the single peak intensity is susceptible to external interference.We develop herein a general strategy for sensing of H₂S utilizing post-functionalization modification of a MOF UiO-66-（COOH）₂ with Eu3,and Cu²⁺ ions.The MOF Eu³⁺/Cu²⁺@UiO-66-（COOH）₂ simultaneously displays the characteristic Eu³⁺ sharp emissions and the broad ligand-centered（LC）emission.Because H₂S can strongly increase the fluorescence of Eu³⁺and quench the broad LC emission through its superior affinity for Cu²⁺ ions,the MOF Eu³⁺/Cu²⁺@UiO-66-（COOH）₂ exhibits low detection limit（detection limit,5.45 μM）,high selectivity and fast response（response time,30 s）to H₂S detection over other environmentally and biologically relevant species under physiological conditions.Furthermore,this approach for fluorescence turn-on sensing of H₂S is expected to extend to other water stable MOFs containing uncoordinated-COOH.The overall luminescence intensity of Eu³⁺/Cu²⁺@UiO-66-（COOH）₂ is weak after the incorporation of Cu²⁺.Here,we propose the potential of using nanoscale fluorescent MOF composites Eu³⁺/Ag⁺@UiO-66-（COOH）₂ as a logic platform for tentative diagnosis of asthma by detecting the biomarker H₂S.This INHIBIT logic gate based on Eu³⁺@UiO-66-（COOH）₂ can be produced by choosing Ag⁺ and H₂S as inputs and by monitoring the fluorescent signal（I615）as an output.Our fluorescent studies indicate that the Eu³⁺/Ag⁺@UiO-66-（COOH）₂ exhibits excellent selectivity,low detection limit（detection limit,23.53 μM）,and real-time（response time,30 s）in situ detection of H₂S.Further,cell experiments shows that the Eu³⁺/Ag⁺@UiO-66-（COOH）₂ possesses favourable biocompatibility that are suitable for the detection of biomarker H₂S in vivo,as demonstrated by the successful detection of spiked H₂S in the diluted serum samples.In order to solve the problem that the powder sample is used for fluorescence detection with high detection limit.Based on 2-nitroterephthalic acid（H₂BDC-NO₂）,Al-MIL-53-NO₂ was designed and synthesized.Herein,we report a rare example of using flexible MOF-based mixed-matrix membranes（MMMs）as a fluorescent turn-on sensor for the detection of hydrogen sulfide（H₂S）.These MOF-based MMMs are readily prepared by mixing a highly stable aluminum-based nano-MOF（Al-MIL-53-NO₂）into poly（vinylidene fluoride）（PVDF）with high loadings up to 70%.Unlike the intrinsic fragility and poor processability of pure-MOF membranes,these MMMs exhibit desirable flexibility and processability that are more suitable for practical sensing applications.The uniform distribution of Al-MIL-53-NO₂ particles combined with the permanent pores of MOFs enable these MMMs to show the good water permeation flux and consequently have a full contact between the analyte and MOFs.The developed MMM sensor（70%MOF loading）thus shows a highly remarkable detection selectivity and low detection limit for H₂S with an exceptionally low detection limit around 92.31 nM,three orders of magnitude lower than the reported powder-form MOFs.更多还原