| In present research,a procedure of post-synthetic modification of metal organic frame?MOFs?by molecularly imprinted polymer was studied to prepare MIPs@ED-MIL-101 composite material.The adsorption capacity and adsorption selectivity for this novel material was explored.To achieve this procedure,a metal organic frame MIL-101 was selected as the matrix and a molecular imprinted polymer was grafted onto the surface of amino-modified MIL-101.Adsorption kinetics and adsorption selectivity of this novel MIPs-MOFs composites toward target molecules were studied.Binding site distribution on the surface of the materials was measured and solid phase extraction?SPE?applicapability for the composites material investigated.?1?Morpholine imprinted polymer was successfully grafted onto the surface of metal organic skeleton MIL-101 to produce a novel imprint composite material.Adsorption equilibrium for this material toward the template can be reached within 150min,with a equilibrium adsorption capacity of 183.3mg/g.Scatchard analysis indicated that there were mainly two types of adsorption sites on the surface of this imprint composite material.The equilibrium dissociation constant K and the maximum apparent adsorption capacity Qmaxfor the high affinity sites were 0.5679 g/L and 326.5 mg/g,while the K and Qmaxvalues for the low affinity sites were 2.493 g/L and 562.9 mg/g,respectively.The selectivity factors of imprinted materials toward morpholine were 2.47,2.48 and 2.24 in relation to the oxides of methyl morpholine,ethyl morpholine and methyl morpholine,respectively.When the MOFs-MIPs composite was used in the solid phase extraction,the recovery of morpholine through single step elution under optimized conditions was 82.44%,showing a high enrichment efficiency.Additionally,this material could be reused for many times without a large loss in adsorption capacity.?2?A novel hexaldehyde imprinted polymer was successfully prepared by surface imprinting technology using ED-MIL-101 as the carrier.Adsorption kinetics showed that adsorption equilibrium could be reached within 240min.Adsorption test indicated the saturated adsorption capacities of 18.52mg/g and 11.96 mg/g for the molecularly imprinted and non-imprinted composites toward the template,respectively.By scatchard analysis,two main types of binding sites were found in the molecularly imprinted polymer matrix.For the high affinity sites,the dissociation constant and the maximum apparent adsorption capacity were 2.842×10-2mg m L-1and 31.38 mg g-1,and for low affinity sites,the dissociation constant and the maximum apparent adsorption capacity were 1.972×10-2mg m L-1and 14.43 mg g-1,respectively.Selectivity coefficients of imprinted composites toward template molecules were 2.51and 1.92,in relation to n-hexanol and n-valeraldehyde,respectively.When this material was used as an adsorbent for solid phase extraction?SPE?,the loaded amount of hexyl aldehyde was higher than that on the non-imprinted composites and the recovery of target compound obtained by using single step solid phase extraction under optimized conditions was up to 54.3%,indicating a high enrichment effect.In addition,the novel imprint material had been shown with a good repeatability after many times utilization.?3?A nicotine-diethyl nitrosamine double template imprint-modified metal organic skeleton composite was prepared with amino-modified metal organic skeleton ED-MIL-101 as the carrier.The imprint-modified MIL-101 appeared microsphere shape.Adsorption kinetics showed that the adsorption equilibrium can be reached within 1 h for nicotine and 1.5h for diethyl nitrosamines.Adsorption capacities for this imprint-modified composite material toward nicotine and diethyl nitrosamines were64.13 and 48.52 mg g-1,respectively.Scatchard analysis showed that there were mainly two types of sites on the surface of this composite material,of which the high affinity sites was mainly generated by imprint reaction and the low affinity sites mainly resulted from randomly distributed functional monomers.Freundlich model fitting revealed a high heterogeneity of the imprinted site energy distribution in the imprinted polymer matrix.Selectivity factors for the imprint composite material toward diethyl nitrosamines in relation to pyridine and m-methyl-pyridine were 3.300 and 3.413,respectively.The competitive adsorption capacities of the imprint composite material toward nicotine and diethyl nitrosamines were 34.31 and 29.77 mg g-1,respectively.During solid phase extraction with this imprint composite material as adsorbents,nicotine and diethyl nitrosamines were mainly recovered in the elution stage of 4×1.0m L methanol-water?2:1,v/v?with recovery of up to 71.6%and 69.4%,respectively,indicating this composite material a good enrichment and separation efficiency. |
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