Metal-Organic Frameworks For Sustained And Controlled Release Of Fragrances

In recent years,with the development of national living standards,fragrances have been widely used in various aspects of life.However,most of the fragrances are volatile,so it is necessary to control their release in many applications.Loading fragrances into carriers has been a common way to modulate the release rate of fragrances,the key is to find proper carriers according to the applications.Metal-organic frameworks(MOFs),a new type of carrier with many advantages over other materials such as high specific surface areas and ultrahigh porosity,are one of the most suitable carriers for fragrance loading.Therefore,we herein explore MOFs as fragrance carriers.In the second chapter,a method for synthesizing MIL-101 MOFs with different functional groups by acylation reaction is established.We first synthesized MIL-101(Cr)-NH2 MOFs.Three post-modified MOFs(TC-MIL-101,BC-MIL-101 and OC-MIL-101)with tert-butyl,phenyl,or carboxyl groups were prepared by the reaction of trimethylacetyl chloride,benzoyl chloride,or oxalyl chloride with MIL-101(Cr)-NH2.The acylation percentages in the modified MOFs were around 60%as determined by NMR spectra.The results showed that the morphologies and structures of the modified MOFs were unchanged compared with the initial MOFs.Nitrogen adsorption curves showed that the specific surface areas of MIL-101-NH2 and the three modified samples were 1683,913,936 and 1562 m2/g,respectively,indicating that the specific surface areas decreased to a certain extent after the reactionIn Chapter 3 of the thesis,two ester fragrances,isoamyl butyrate and butyl acetate,and one terpene fragrance,myrcene,were used to estimate the fragrance loading capacities and release behaviors of the three post-modified MOFs.The adsorption capacity of OC-MIL-101,BC-MIL-101 and TC-MIL-101 for isoamyl butyrate was 0.276 0.155 0.176 g/g,respectively.It can be seen that OC-MIL-101 has the higher adsorption capacity for isoamyl butyrate than other two MOFs,and the same phenomenon can also be seen in the ester fragrance butyl acetate.The FTIR results indicated OC-MIL-101 formed strong hydrogen bonding with ester fragrances such as isoamyl butyrate,while computer simulations showed that the binding energy of isoamyl butyrate to OC-MIL-101 was lower than those of the other MOFs,indicating that there was a strong host-guest interaction force between OC-MIL-101 and isoamyl butyrate.The release profile of fragrance shows that release amount of two ester fragrances in OC-MIL-101 was much lower than the other two MOFs after two weeks.Therefore,this kind of host-guest interaction can modulate the release of fragrances.This chapter demonstrates that the release rate of fragrances can be well-tuned by the host-guest interaction between different functionalized MOFs and fragrances.In Chapter 4 of the thesis,we prepared CD-MOF@A4 composites by in-situ growth of cyclodextrin metal-organic framework(CD-MOF)on A4 paper for the first time.The successful growth of CD-MOF on A4 paper was confirmed by various characterization.At the same time,The nitrogen adsorption curve showed that the specific surface area of CD-MOF@A4 is 237 m2/g,which indicates that the composite material has adsorption capacity.Six fragrances were used to test the fragrance loading capacity of CD-MOF@A4 and compared with A4 paper.CD-MOF@A4 had a significantly higher fragrance adsorption capacity than A4.By analyzing the release behavior of cinnamaldehyde,it was found that the free cinnamaldehyde was completely released in about 10 days,while the release amount of cinnamaldehyde in CD-MOF@A4 was only 30%in 21 days,indicating that this composite material had a good effect of slow release of fragrances.The antibacterial effects of CD-MOF@A4 loaded with cinnamaldehyde were assessed on E.coli and S.aureus.CD-MOF@A4/cinnamaldehyde had a good antibacterial effect against both E.coli and S.aureus.Finally,we found that CD-MOF@A4 has a good adsorption performance and can be used to adsorb formaldehyde.Therefore,this chapter invented the in-situ growth of CD-MOF on A4 paper,which gives the paper excellent adsorption capacity.