Synthesis Of MOF-based Fluorescent Composite Materials And Their Application In Chemical Sensing

Metal–organic frameworks（MOFs）,self-assembled from metallic ions（or aggregates）and polyfunctional organic linkers,have been extensively studied over the past two decades.MOFs can be rationally designed and conveniently synthesized,and they have tunable properties which make them promising candidates for many important applications including gas storage and separation,chemical sensing,drug delivery,catalysis,and so on.Recently,while the development of novel MOFs keeps rapid,MOF-based nanoparticles,particularly MOF-based emitting nanoparticles are also greatly investigated.The tunable pores and ultrahigh porosities make MOFs potential host matrices for functional guest nanoparticles.In addition,the MOF structure can prevent guest nanoparticles from aggregation,thus improving the properties of the nanoparticles.As a result,encapsulating functional guest nanoparticles into MOF cavities is a promising strategy to obtain functionalized MOF-based composite materials with advanced properties.Ratiometric fluorescent sensors are based on the measurement of the ratio of fluorescent（FL）intensities under two independent wavelengths,which can efficiently eliminate the influence induced by the variation of excitation light source,unstability of the environment,and fluctuation of the probe concentration.19 This method can greatly improve the detection accuracy.Up to now,ratiometric sensors are commonly designed by the combination of two components with distinct fluorescent emission wavelengths,including carbon dots（CDs）,quantum dots（QDs）,fluorescent dyes,metal cluster,upconversion nanoparticles,MOFs,and so on.In this dissertation,novel MOF-based fluorescent materials were designed and synthesized by combining the hybrid characteristics of MOFs with the specific properties of fluorescent materials,these composite materials were further applied to chemical sensing.1.Synthesis of the QDs/CDs@ZIF-8 composite material and its application in ratiometric detection of Cu2+.A novel ratiometric fluorescent sensor was synthesized via a facile one-pot route by encapsulating red-emitting QDs and blue-emitting CDs with good fluorescence properties into ZIF-8（zeolitic imidazolate framework,one of the classical metal–organic frameworks）.The as-synthesized QDs/CDs@ZIF-8 composite not only possessed the advantages of a RF sensor,but also accumulated target analytes strongly due to the adsorption ability of MOFs.The composite showed good stability and dispersibility in aqueous solution and was further applied to the detection of Cu2+ ions,the linear range was 5–100 n M and the LOD was 1.53 n M.The QDs/CDs@ZIF-8 composite could be simply used for detecting Cu2+ in tap water.2.Synthesis of the Fe₃O₄/Rh B-CDs@ZIF-8 composite material and its application in ratiometric detection of HCl O.A novel magnetic,ratiometric fluorescent nanoprobe was designed and synthesized by encapsulating Fe₃O₄ magnetic nanoparticles（Fe₃O₄ MNPs）and dual-emissive carbon dots into the cavities of zeolitic imidazolate framework（ZIF-8）.The MOF-based nanoprobe combined the advantages of MOFs（strong adsorption ability,accumulating the analytes）,Fe₃O₄ MNPs（magnetic seperation）and ratiometric sensors（eliminating the variabilities caused by the unstability of the instruments and environment）.The MOF-based nanoprobe had good stability and dispersibility in aqueous solution and was further applied to HCl O detection.