| Metal organic frameworks(MOFs)are a porous crystalline material,which are formed by self-assembly of a central metal and an organic bridging ligand through coordination bonds.Compared with other traditional porous materials(such as organic polymers,zeolite materials,porous silica,etc.),MOFs not only have the functional characteristics of organic and inorganic materials,but also have the following unique advantages:high crystallinity,diversity and designability of structure and composition,large specific surface area and ultra-high porosity.These advantages make it have application potential in many fields.Among them,rationally designing stable fluorescent functional MOFs and using them for fluorescence detection is a current research hotspot.The research content of this article is divided into the following two parts according to the hot spot:Firstly,explore the selective detection of nitroaromatic compounds(NACs)by the novel luminescent MOFs,which is a research hotspot;at the same time,understand the sensing mechanism of the interaction between luminescent MOFs and NACs molecules at the molecular level,which is a challenging issue.In the second chapter of this article,diphenylethyne-3,3',5,5'-tetracarboxylic acid(H4EBTC)was used as a bridging ligand and metal scandium ion(Sc3+)to synthesize a highly stable and strong fluorescent MOF—Sc-EBTC by a solvothermal method.It can detect various NACs molecules quickly,high efficiently,and high selectivity by the"turning off"fluorescence mechanism.The detection limits of Sc-EBTC toward 2,4-DNP and 4-NP were quantified to be 5.71 ppb and 6.26 ppb,respectively.Furthermore,to better understand the sensing mechanism,we attempted to use solid-state NMR and X-ray photoelectron spectroscopy to vividly characterize the charge transfer caused by the interaction between NAC molecules and the MOF at the molecular level.Additionally,the“fluorescent test paper”were made successfully for the practical detection of the NACs.This study demonstrates that the MOF constructed from the H4EBTC ligands might be a promising candidate for the detection of trace NACs.Secondly,explore the design of a fluorescent sensor that can detect F-in drinking water with high selectivity and sensitivity.Due to the unique advantages of visual detection(that is,the specific interaction between the sensor and the test object changes the fluorescence color),we rationally designed a MOF with dual emission fluorescence function based on the previous work(Eu/Sc)-EBTC.This MOF can emit ligand-based blue fluorescence and Eu3+-based red fluorescence at the same time,and it showed high selectivity and sensitivity to F-(detection limit=16.4 ppb).The sensing mechanism was ascribed to the high affinity between F-and Eu3+in(Eu/Sc)-EBTC,which leaded to a reduction in the efficiency of energy transfer from the ligand to Eu3+in the“antenna effect”and demonstrated by PXRD patterns and X-ray photoelectron spectroscopy.Besides,“fluorescent test paper”was made also for the practical detection of F-.This is a quick and preliminary method for non-experts in remote areas to detect F-in water,and this is also an area worth trying.This study demonstrates the effectiveness of constructing dual-emission fluorescent MOFs sensors based on the design concept of different interactions between the target species and the ligand and metal center. |
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