Synthesis And Performance Study Of Al(?) And Ti(?)-metal Organic Framework Compounds Based On Carboxylic Acid Ligands

Energy shortage and environmental pollutions caused by burning fossil fuel have become worldwide concerns.Solar energy is the inexhaustible and clean energy source worldwide.UV light accounts for only 4%while visible light contributes 43%of solar energy.Thus preparing and developing visible light absorbing semiconductors which can be used in converting light into electricity or used as photocatalysts to store solar energy into useful chemicals is rather imperative.Metal-organic frameworks(MOFs)can be synthesized as visible-light absorbing semiconductors due to their designability in structures and functionalities.Studies relating to the semiconducting behavior of MOFs are still in their initial stages,and further investigations are highly desired.Al(III)and Ti(IV)carboxylate metal-organic frameworks have attract researcher's attention due to their high water and thermal stability.In addition,they can be designed and synthesized as visible-light semiconductors by changing the ligand.But the single crystals of Al(III)and Ti(IV)MOFs are very difficult to obtain,which are used to determine their structure by single-crystal XRD diffraction analysis.This obstacle has greatly slowed down the development and application of these MOFs.Up to now,only 40 of Al(III)and and 4 of Ti(IV)carboxylate metal-organic frameworks are known.In this thesis,we obtained following results:1.We found and demonstrated that using HF or HCOOH,or HF and HCOOH mixed acid aided by the orthogonal experimental design method is an effective and general method of obtaining single crystals of Al-MOF,which could be measured using common single-crystal XRD diffractiontometer.2.Using the above method,single crystals of an known(MIL-53)(previously obtained as powders),two new Al-MOFs based on H4TCS(tetrakis(4-carboxyphenyl)silane)(MOF 1 and 2)were obtained.A new Al-MOF(MOF 3)based on H3TMB(1,3,5-Tris(carboxymethoxy)benzene)was obtained.However,the single crystals of MOF 3 were not obtained.3.A new Ti-MOF based on H3TIB(1,3,5-Tris(4-carboxyphenyl)benzene)was obtained.However,the single crystals of MOF 4 were not obtained.4.MOF 1-4 all absorbs vible light and their band gaps were determined.MOF 1-2 were found having good photoelectric properties,and MOF 1 have good photocatalytic activities in water splitting under visible light.