Designed Synthesis And Properties Of Series Of MOF-5 Analogues With Moisture Resistance

Metal-organic frameworks?MOFs?,as a new type of crystalline porous materials,with high porosity and special surface area,and also with diverse and flexible structures,exhibit a wide variety of potential applications in heterogeneous catalysis,gas storage,molecular selective absorption and separation,luminescence,and drug delivery.Although the past two decades have witnessed great advances of MOFs,with the development of research,weak stability of some MOFs has considerably limited their further application and commercialization.Due to lack of moisture resistance,most of the reported MOFs are sensitive to water content.The framework decomposes gradually when the environment contains high moisture level.Hence,it is important to improve the moisture resistance of MOFs materials for practical application.It has been reported that introducing some hydrophobic substituent groups will improve the water-stability of MOFs.Our work devotes to constructing new water-stable MOFs with the hydrophobic groups.Series of linear dicarboxylic acid ligands containing aryl hydrophobic groups had been designed and synthesized,which were used to successfully construct classical MOF-5 analogues.Surprisingly,these MOFs exhibit good moisture resistance.The main works were as followed:?1?Four bithiophene-dicarboxylic acid ligands containing aromatic ring substituents were designed and synthesized,which are 3-?4-bromophenyl?-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylic acid?L1?,3-?4-methoxyphenyl?-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylicacid?L2?,3-methyl-4-?naphthalen-2-yl?thieno[2,3-b]thiophene-2,5-dicarboxylic acid?L3?and 3-?4-biphenyl?-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylic acid?L4?.The intermediates of aryl?-diketone and bithiophene-dicarboxylates were synthesized from aryl acetone,and finally the target ligands were obtained by the hydrolysis of bithiophene-dicarboxylates.The results of FT-IR spectra and ¹HNMR spectra determined the molecular structures of the corresponding intermediates and ligands.The synthesis route is convenient,high yield and in the mild conditions,and can be used to synthesize other similar ligands.?2?Under solvent-thermal synthesis,four novel MOFs,Zn₄O?L1?₃?MRMOF-1?,Zn₄O?L2?₃?MRMOF-2?,Zn₄O?L3?₃?MRMOF-3?and Zn₄O?L4?₃?MRMOF-4??MRMOF,ab.of moisture resistant MOFs?,have been successfully synthesized.Their structures were characterized by the single-crystal X-ray diffraction.PXRD analysis shows that hydrophobic aryl groups with big sterohindrance can protect Zn₄O clusters from attack of water molecules,which give MOFs good moisture resistance.N₂ adsorption study indicates that these compounds exhibit high porosity.In addition,the fluorescence properties of compounds were also studied.In conclusion,this paper reported series of moisture-resistant MOF-5 analogues,which are constructed by self-designed and synthesized liner dicarboxylic acid ligands with hydrophobic aryl groups.The significant improvement in stability will help us to develop their functional properties of these MOFs in the future,so that such materials are expected to be truly used in practice.