Preparation And Application Of Functionalized Metal Organic Frameworks And Its Hybrid Imprinted Recognition Materials

With the development of new functional materials,the application of materials possessing high adsorption capacity and molecular recognition ability in the field of pesticide detection has become hot researching focus.Metal-organic frameworks(MOFs)with the advantages of high surface areas,nanoscale and easy modification not only efficiently enrich pesticide molecule,but also can be in conjunction with other nanomaterials to form functional composites.Molecular imprinting polymers(MIPs)with predetermination,recognition and practicability could be used as perfect solid phase extraction materials,which specificly seperate analytes from complex matrix.However,MOFs have deficiencies including low stability,poor hydrophilicity,complex synthetic conditions and lack of specific recognition;traditional MIPs are greatly limited due to low adsorption capacity,slow mass transfer and unavoidable template leaking.the key to overcome above limitations are the mature preparation strategy and functional combination.These materials are also the basis for developing new pesticide detection technology and making up for the shortage of existing methods.In this paper,different synthetic strategies were used for prepareing MOFs and magnetic MOFs composites,MIPs and MOFs@MIPs core-shell composites,simplifing the synthetic process,improving the performance of materials.Also,the obtained materials were explored to enrich neonicotinoids or triazole fungicides in mass spectrometric technique and SERS detection technique.The results of this study are as follows:(1)Fe3O4/ZIF-67 composites were successfully synthesized by in-situ polymerization method at room temperature.The magnetic composite was applied to the adsorption of triazole fungicides in environmental samples,and the adsorption mechanism was preliminarily discussed.The results showed that the main interaction between Fe3O4/ZIF-67 and analytes was ?–? accumulation interaction.Under the optimum conditions(solution p H 7,25 min as adsorbing time,3 m L 2% acetic acid acetone as elution),ten kinds of fungicides with R2 higher than 0.9938,were in good linear relationship between 5-500 ng/m L.Most of the spiked recoveries were from 70% to 110%.This experiment not only provided a simple strategy for the preparation of magnetic MOFs composites,but also established simple and high sensitive mass spectrometry method to detect triazole fungicides in environmental sanples based on magnetic solid phase extraction process.(2)The application of “one-pot method” to synthesize magnetic ZIF-67/GO composite was explored.The metal ion Co2+ with positive charge and GO,Fe3O4 nanoparticles(-OH)with negative charge were stabilized by electrostatic interaction,forming the magnetic composites.The morphology and chemical composition were characterized by scanning electron microscopy,transmission electron microscopy and infrared spectroscopy.The results showed that the ZIF-67 and magnetic particles were well attached to the surface of GO.The magneitic composite was applied to enrich neonicotinoids,and the adsorption properties were preliminarily evaluated.Also,GO with rich hydrophilic groups could improve the properties of ZIF-67 materials,providing useful routine to improve the hydrophilic properties of other MOFs.(3)Uio-66 material were successfully prepared by solvothermal method,and this material in the enrichment of neonicotinoids was also explored.The results showed that the synthesized Uio-66 had excellent thermal stability(400 ?),high specific surface areas(843.8 m2/g),and regular uniform size(100-150 nm).Based on dispersive solid phase extraction,the optimum adsorption conditions were: 3 m L acetone as elution,p H as 9,Na Cl as 15%(w/v)and adsorption time as 5 min.The results showed good linear relationship with R2 greater than 0.9916,the better recoveries with 73.7%-119.0%(RSDs: 2.4%-17.1%).The developed method showed fast enrichment towards insecticides and high sensitivity,not only introducing a new type of perfect adsorbent with highly reused times for dispersed solid phase extraction,but also providing referenced experiments for the detection of trace contaminants in environmental samples.(4)A new dummy-template molecularly imprinted polymer with triadimefon molecules as the template and methacrylic acid as functional monomer was successfully synthesized by precipitation polymerization method.MIP-SERS combined with multivariate statistical analysis was applied to detect bitertanol in complex matrix.The results showed that the synthesized MIPs had uniform morphology and diameter(2 m),and high adsorption capacity and good specificity.Also,the gold nanoparticles possessing huge SERS enhancement factor were successfully synthesized by “citric acid reduction” method.With increased initial concentration,the adsorption capacity of MIPs and NIPs towards bitertanol also improved;the maximum adsorption capacity of MIPs was 2.21 mg/g,1.5 times of NIPs(1.55 mg/g).The intensity of four characteristic peaks(760,985,1190,1279 cm-1)all increased with the increasing spiked level in the cucumber and peach matrix.Through the PCA eigenvectors analysis,PC1 were 0.359 and 0.36 in cucumber and peach,well explaining changes in the SERS spectrum.The established MIP-SERS method not only provided a rapid method for detecting bitertanol in agricultural products(< 15 min),but also provided a specific recognition material for further application of SERS technology in complex matrix.(5)The surface imprinting strategy was applied to synthesize Uio-66@MIPs composites.Based on imidacloprid as the template molecule,MAA and styrene as double functional monomer,MIPs layer was tried to polymered on the surface of Uio-66.In the synthesis process,enrichment and selective recognition of Uio-66@MIPs with different functional monomers(MAA and styrene)towards neonicotinoids were compared.And the loading solvents,washing solvents and eluting condition were optimized.The characterized results showed that MIP layer were successfully polymerized onto the surface of Uio-66,and the synthesized composites was core-shell structure with uniform size(500-600 nm)and good thermal stability(350 ?).Through study on the adsorption capacity of neonicotinoid pesticides,the extraction efficiency of the similar structure of clothianidin,imidacloprid,acetamiprid and thiacloprid were 83%,95%,85% and 96% respectively,higher than dinotefuran,nitenpyram and thiamethoxam(25%,1% and 52%),indicating this composites had large adsorption capacity and specific recognition characteristics.The SPE column was prepared based on the core-shell composites.Under optimal conditions,the recoveries with spiked 5,10,20 ng/g,were good with 71.0%-105.3%,72.0%-84.6% in cucumber and apple,respectively.A new SPE-HPLC-MS/MS method based on Uio-66@MIPs core-shell composite was established for the determination of neonicotinoid pesticides in cucumber and apple.Uio-66@MIPs core-shell nanocomposites with specific recognition for triazole fungicides were furtherly obtained through MIP layer polymerized on Uio-66(triadimefon as template molecule,methacrylic acid as the functional monomer)by above strategy,and the composites were explored to enrich triazole fungicides in agricultural products.The diameter of composites was 400-500 nm,possessing excellent stability(350 ?).Under the optimal loading solvent(20% ACN solution),washing solvent(5 m L pure water)and elution solvent(3 m L methanol),for example in cucumber matrix,the linear relationships were good with R2 greater than 0.9946 about ten kinds of triazole fungicides;The LODs(S/N =3)and LOQs(S/N = 10)were 0.007-0.16 ng/m L and 0.02-0.5 ng/m L,respectively.With spiked 5,10,20,40 ng/g levels,the recoveries all met the methodological requirements(71.6%-102.0% in cucumber and 71.3%-90.0% in apple).A highly enriching detecting method towards ten triazole fungicides for cucumber and apple matrix was successfully established.MOFs@MIPs core-shell composites based on imidacloprid and triazole fungicides were successfully synthesized.The established methods for their monitoring and evaluation of residues of neonicotinoid pesticides or triazole fungicides in agricultural products,provides rapid-efficient identification technique.More importantly,MOFs was introduced into enrichment and detection of analytes in complex matrix,providing a simple method for synthesizing MOFs@MIPs core-shell structure.This synthetic strategy innovatively endowed MOFs with specific recognition and furtherly improved the adsorption ability of MIPs,providing vital references for other MOFs in the application of complex matrix.