State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, the Chinese Academy of Sciences, Wuhan 430071, China.
Phys Chem Chem Phys. 2010 Apr 21;12(15):3895-903. doi: 10.1039/b915401a. Epub 2010 Feb 24.
Extra-framework aluminium (EFAL) species in hydrated dealuminated HY zeolite were thoroughly investigated by various two-dimensional solid-state NMR techniques as well as density functional theoretical calculations. (27)Al MQ MAS NMR experiments demonstrated that five-coordinated and four-coordinated extra-framework aluminium subsequently disappeared with the increase of water loading, and the quadrupole interaction of each aluminium species decreased gradually during the hydration process. (1)H double quantum MAS NMR revealed that the EFAL species in the hydrated zeolite consisted of three components: a hydroxyl AlOH group, and two types of water molecule (rigid and mobile water). (1)H-(27)Al LG-CP HETCOR experiments indicated that both the extra-framework and the framework Al atoms were in close proximity to the rigid water in the fully rehydrated zeolite. The experimental results were further confirmed by DFT theoretical calculations. Moreover, theoretical calculation results further demonstrated that the EFAL species in the hydrated zeolite consisted of the three components and the calculated (1)H NMR chemical shift for each component agreed well with our NMR observations. It is the rigid water that connects the extra-framework aluminium with the four-coordinated framework aluminium through strong hydrogen bonds.
水合脱铝 HY 沸石中骨架外铝（EFAL）物种通过各种二维固态 NMR 技术以及密度泛函理论计算得到了深入研究。(27)Al MQ MAS NMR 实验表明，随着水负载的增加，五配位和四配位的骨架外铝逐渐消失，并且各铝物种的四极相互作用在水合过程中逐渐减小。(1)H 双量子 MAS NMR 表明，水合沸石中的 EFAL 物种由三种成分组成：羟基 AlOH 基团和两种类型的水分子（刚性和可移动水）。(1)H-(27)Al LG-CP HETCOR 实验表明，在完全水合的沸石中，骨架外和骨架内的 Al 原子都与刚性水接近。实验结果进一步通过 DFT 理论计算得到证实。此外，理论计算结果进一步表明，水合沸石中的 EFAL 物种由三种成分组成，每个成分的计算(1)H NMR 化学位移与我们的 NMR 观察结果吻合良好。正是刚性水通过氢键将骨架外铝与四配位骨架铝连接起来。
