AFI型分子筛吸附H_2分子的密度泛函理论研究

Density Functional Theory Studies of H_2 Adsorbed in AFI Zeolite

采用基于密度泛函理论的量子化学计算,对AFI型分子筛吸附H2分子的不同吸附模式进行理论探讨.结果表明,H2分子在分子筛孔道内的吸附属于物理吸附范畴.由于相互作用较弱,吸附前后H2分子和AFI分子筛的几何结构变化都较小.根据结合能的计算结果,S1～S5模式中H2分子吸附均为放热过程,其中S1模式放出热量最多;在考虑基组重叠误差效应时S6为吸热过程.AFI分子筛吸附H2分子形成的复合物的前线轨道主要由分子筛原来相应轨道贡献,前线轨道在H2分子上几乎没有分布.不同吸附模式对AFI型分子筛吸附H2分子形成的复合物的电子性质影响很小.

He adsorption in AFI zeolite with different adsorption models were studied theoretically by means of the quantum chemistry calculations based on the density functional theory. It was found that the adsorptions of H2 in the channels of the zeolite belonged to the physical adsorption. The geometrical struetures of H2 and the AFI zeolite both changed very little when H2 was adsorbed. According to the results of the calculated binding energies, the adsorptions of H2 were exothermic for S1- S5 models, among which S1 was the most exothermic process. S6 was endothermic when the basis set superposition error effect was considered. The frontier orbitals of the hybrid systems for H2 adsorption in the AFI zeolite were all derived from the corresponding orbitals of the zeolite, and nearly no distribution was found in the adsorbed H2. The adsorption models had no significant effect on the electronic properties of the hybrid systems.