Synthesis, Structure And Properties Of Novel Metal-organic Frameworks

Metal-organic frameworks （MOFs）, also called porous coordination polymers,have received intense attention due to their enormous variety of interesting structuresand great potential applications as functional materials. These materials can be appliedpotentially in gas storage, separation, ion exchange, catalysis, sensor, drug delivery andso on. To obtain predictable frameworks and properties, a large number of researchesare being focused on constructing novel metal-organic frameworks by using functionalmetal ions and versatile organic ligands.Based on the principle of molecular engineering, we have focused our study onthe synthesis, structures and multifunctional properties of MOFs with charmingtopologies. In this dissertation, we have prepared5novel metal-organic frameworks bydifferent triazine derivatives, and analyzed their crystal structure as well as researchedtheir properties. These results will be introduced from the following issues:1. Two microporous MOFs [Cd₃（L）2（H₂O）6]·1.5H₂O·2EtOH·DMF （1） and[Zn3（L）2（H₂O）2]·3H₂O·TEA·2DMF （2） by2,4,6-tris-（4-Carboxyphenoxy）-1,3,5-triazine （H₃L） have been successfully synthesizedand characterized. Compound1and2display high thermal stability and permanentporosity. The gas sorption measurement indicate that compound1and2exhibitedselective sorption capabilities for CO₂over CH₄and N2, and adsorbed considerableamounts of H₂at low temperature. These two compounds also show high sorptioncapabilities for water, methanol, and ethanol vapors, which proves that they are goodporous material with flexible frameworks. Furthermore, the emissions of compound1and2with blue shift.2. Based on2,4,6-tris（3,5-dicarboxylphenylamino）-1,3,5-triazine （H₆L）， theunique rht-MOF [Zn（H₆L）（H₂O）3]·xGuest （3） which has cages structure has beensynthesized.3. To increase the gas uptake capacity, current efforts are evoted to enhancing thegas-binding affinity in MOFs. Strategies reported include framework interpenetration,ligand functionalization, construction of size/shape specific pores and polar pore walls, and in particular, incorporation of pen metal sites. A functional MOF encompassingcavities and windows decorated with Lewis basic sites （e.g., OH, COOH,N-donating groups and triazine nitrogen atoms, etc.） could potentially lead to enhancedCO₂sorption energies. Considering the thought above, we designed and synthesized aflexible ligand,2,4,6-tris-（4-carboxyphenoxy）-1,3,5-triazine. Based on this ligand, twonovel MOFs,[Cd（H₄L）]·2H₂O （4） and [Cu（H₄L） H₂O]（5） have been synthesized.Compound4has exposed carboxyl oxygen, which will have a good role in promotingCO₂and H₂adsorption. Compound5is3D cage structure, has great prospect foradsorption, separation and catalytic.