Molecular diffusion in nanoporous materials can be understood as series of dynamic hopping or exchange motions of molecules between different discrete sites. Exchange NMR offers the spectral resolution to distinguish between these different sites, based on isotropic and anisotropic NMR interactions that manifest differences in the local chemical or structural environments of molecules at different sites or their local orientations. Such interactions facilitate the observation of distinct adsorption environments and provide insights on the number and distributions of distinct types of environments and the geometries and motional correlation times of local hopping events between different sites. The temporal range accessible by exchange NMR is governed by the time required for the observation of the NMR signal (< 1 ms) and the return of the nuclear magnetic polarization to thermal equilibrium (typically several seconds). Over such timescales, this permits slow molecular exchange processes between local environments to be probed in great quantitative detail. The resulting insights on dynamic exchange or hopping of atoms, molecules, or ions in nanoporous solids provide a basis for understanding processes that occur over longer length and time scale, which ultimately account for their macroscopic diffusion properties.

纳米多孔材料中的分子扩散可以理解为一系列分子在不同离散位点之间的动态跳跃或交换运动。交换NMR基于各向同性和各向异性NMR相互作用提供了区分这些不同位点的光谱分辨率，这些相互作用表明分子在不同位点或其局部方向上的局部化学或结构环境存在差异。这种相互作用有助于观察不同的吸附环境，并提供有关不同类型的环境的数量和分布以及不同站点之间局部跳跃事件的几何形状和运动相关时间的见解。交换NMR可访问的时间范围受NMR信号观察所需的时间（< 1毫秒），核磁极化恢复到热平衡（通常几秒钟）。在这样的时间尺度上，这允许以大量定量细节探究局部环境之间的缓慢分子交换过程。对纳米多孔固体中原子，分子或离子的动态交换或跳跃的最终见解为理解更长的长度和时间范围内发生的过程提供了基础，这些过程最终解释了它们的宏观扩散特性。