含羧酸镁(钙)官能团的多孔芳香骨架材料储氢性能的预测

Predicting Hydrogen Storage Performances in Porous Aromatic Frameworks Containing Carboxylate Functional Groups with Divalent Metallic Cations

用MP2方法,TZVPP基组以及基组重叠误差(BSSE)校正计算了氢分子与修饰在多孔芳香骨架(PAF)上的羧酸镁、羧酸钙官能团的相互作用,并建立了描述这一相互作用的分子力学力场.在此基础上用巨正则系综蒙特卡洛(GCMC)模拟预测了氢气在该种新型PAF材料上的吸附等温线.量子化学计算结果表明,每个羧酸镁、羧酸钙官能团分别可以提供13、14个氢分子吸附位点,与每个氢分子的平均结合能在8kJ·mol-1左右.通过比较不同温度和压力下材料的绝对吸附量和超额吸附量发现,在PAF骨架中引入羧酸镁、羧酸钙官能团可以显著提高材料的综合储氢性能,达到并超过了美国能源部提出的2015年储氢标准.同时该工作还揭示了氢吸附量与材料的表面积、空腔体积和分子作用强度间的复杂关系.

We report force field predictions for the hydrogen uptakes of porous aromatic framework（PAF） materials containing carboxylate functional groups with divalent metallic cations.The ab initio calculations were performed on our proposed functional groups and hydrogen molecules using the MP2 method with the TZVPP basis set and basis set superposition error（BSSE）correction.A force field was developed based on the ab initio energetic data.The resulting force field was applied to predict hydrogen adsorption isotherms at different temperatures and pressures using the grand canonical Monte Carlo（GCMC） method.Each functional group of divalent metallic cations and two carboxylic acid groups provided 13（Mg） or 14（Ca）binding sites for hydrogen molecules with an average binding energy of 8 kJ·mol -1 per hydrogen molecule.The predicted hydrogen adsorption results were improved remarkably by the functional groups at normal ambient conditions,exceeding the 2015 target set by the department of energy（DOE）of USA.This work reveals the complex relationship between hydrogen uptake and surface area,and the free volumes and binding energies of different materials.