# Dynamics of molecules confined in nanocages. A deuteron NMR study at high temperature

## TL;DR

This study uses deuteron NMR spectroscopy to investigate molecular mobility within nanocages of zeolites at high temperatures, revealing transitions from translational to rotational motion and the effects of interactions on molecular dynamics.

## Contribution

It provides new experimental insights into molecular behavior in nanoconfined environments and discusses the applicability limits of NMR methods for such studies.

## Key findings

- Transition from translational to rotational mobility with decreasing temperature
- Evidence of D2O clustering and CD3OD trimer formation
- Correlation between molecule immobilization temperature and interaction strength

## Abstract

Our published and new experimental results by means of deuteron NMR spectroscopy in studies of molecular mobility in confinement are summarized and annalysed. Conclusions about limits of applicability of methods in disclosing several features are achieved. A set of molecules: D2, CD4, D2O, ND3, CD3OD and (CD3)2CO was chosen and introduced into zeolites with faujasite structure. Measurements of deuteron spectra and relaxation in function of loading and temperature provide a wealth of cases. A tranistion from translational into rotational mobility on decreasing temperature was a common obsevation. Fast magnetization exchange between two subsystems with different mobility was considered as a model. Existence of D2O clusters and trimers of CD3OD was a particularly significant evidence for importance of mutual ineractions. Evolution of spectral components, derivation of the activation energy and T1/T2 ratio are among analysed features. Choice of the zeolite, eg. NaY or NaX, introduces specific inertactions with the zeolite framework. Temperature at wich molecules become immobilized on cage walls is related to the strength of the interactions. On increasing temperature we may observe features like for layers of liquid on cage walls and gaseus state. In general properly chosen molecules may be used for characterization of host microporous systems.