Hydrogen Adsorption Study On Metal-Organic Frameworks

Porous metal organic framework compounds in the field of materialsscience is a new important development direction being increasingly broadattention. Although porous metal organic framework compounds less than thethermal stability of microporous inorganic matrix materials, in the traditionalhigh-temperature catalytic application of the restrictions, but in somenon-traditional areas, such as nonlinear optical materials, magnetic materials,superconducting materials, and hydrogen storage materials, and other newmaterials application prospects are continue to be developed.In this study, MOF-5 compounds have been synthesized andCharacterization fine structure analysis, assay and the use of computersimulation and MOF-5 the pore structure and pore size distribution; Accordingto the characterization of the experimental data with computer simulation todetermine MOF-5 the microscopic crystal structure parameters, Atomicstructure and atomic coordination between the relations on the basis of MOF-5the valence band structure, density of states and electron density, and otherphysical and chemical properties calculation; Study of hydrogen storage andhydrogen storage properties and the structural stability, and its temperature and pressure hydrogen performance.The results show that the pore structure MOF-5 micro-based, isotherm, inthe relatively pressure P/P0 nearly 1 slightly upswept, appeared high pressuretail, May be due to MOF-5 also the presence of small amounts of porous orholes caused. Samples from the pore size distribution curve can be seensamples pore structure which contains large amounts of microporous, and themain distribution in 6-10 (?).Samples of the surface area 889．62m2/g,microporous rate, the total pore volume. Microporous rate and the averagepore diameter of 0．41, 0．50, 0．82 and 2．23．Based on the density functional theory, the use of self-consistentprojection augmented plane-wave method, Calculation of terephthalic acid/zinc complex (MOF-5) Body geometric and electronic structure. MOF-5predicted by the theory is a direct bandgap semiconductor, valence bandmaximum (VBM) and the conduction band minimum (CBM) all located at theG (0,0,0) , direct energy gap of about 3．17eV, indirect energy gap of about3．18eV. Through the optimization of MOF-5 crystal structure analysis, MOF-5found that the crystal structure of the benzene ring spaces along the rightdirection by tension, at the same time along the vertical direction by theright-compression, Note bonding process of terephthalic acid moleculesbenzene ring a certain deformation. While optimizing the MOF-5 crystal totalstate density map and the density-wave state maps and Mulliken charge pmAnalysis found Zn-O1 the bond energies greater than Zn-O2; Zn atoms 4p orbit with electronic distribution, that the Zn s, p and d orbitals participate inthe bonding.Using density functional theory (GGA/PW91) hydrogen molecules in theadsorbed MOF-5, Detailed study of adsorption sites interaction energy, cometo the preferential adsorption of hydrogen molecules in OZn4 peak near thecorner of (Ⅰ) then adsorption of benzene ring position (Ⅱ). hydrogen oxygenmolecules in the OZn4 corner location for the adsorption energy of about-12．0kJ/mol. Benzene location of the adsorption energy of-8．0kJ/mol.Benzene molecular hydrogen in the reverse position to 0．96kJ/mol fusion withthe experimental value of 1．00kJ/mol compared attacks, the major cell with asmall cell, hydrogen molecules can reverse respectively, 2．54kJ/mol and2．6kJ/mol. The experimental results than 1．67kJ/mol, Note to reverse largeadsorption more powerful. The trend with the experimental data, namelyhydrogen molecules in the MOF-5 adsorption corner position than in a morestable position of the benzene ring.