# Dynamics of Ligand and Guest in 1D Hg(II)‐Bispidine Coordination Polymers With Different Topologies Investigated by Solid‐State NMR

## TL;DR

This study uses solid-state NMR to compare how chlorobenzene moves in two different 1D coordination polymers, revealing how their structures affect adsorption efficiency.

## Contribution

The paper introduces new insights into host-guest dynamics in 1D coordination polymers using solid-state NMR techniques.

## Key findings

- Chlorobenzene shows fast isotropic motion in 1-ClBz but slower anisotropic motion in 2-ClBz.
- Stronger interactions and smaller free volume in 2-ClBz restrict guest dynamics.
- Ligands are rigid in both CPs, except for methyl groups undergoing fast motions.

## Abstract

1D coordination polymers (CPs) made of parallel, weakly interacting chains have been recently proposed for the selective adsorption of volatile organic compounds (VOCs), one of the main sources of air and water pollution. Since the efficiency of adsorption for VOC removal strongly depends on the specific and stable interactions between the volatile species and the CP framework, the characterization at the atomic level of host‐guest interactions and guest dynamics is of particular interest. Here, low‐ and high‐resolution solid‐state NMR experiments were applied to acquire information on ligand and guest dynamics for two 1D CPs (1‐ClBz and 2‐ClBz), both containing a bispidine organic ligand, Hg(II) as a metal center, and chlorobenzene trapped within the framework, but featuring different topologies. By combining analyses of on‐resonance 1H free induction decays (FIDs), 1H and 13C longitudinal relaxation times, and 2H quadrupole echo spectra, it was found that chlorobenzene undergoes fast dynamics, mainly isotropic, in 1‐ClBz, while it shows slower anisotropic motions in 2‐ClBz, indicating stronger interactions between framework and adsorbate in the latter associated with the lower available free volume. Ligands are quite rigid for both CPs in the investigated frequency scale, apart from methyl groups, which undergo fast motions about their ternary symmetry axes.

1D CPs are promising materials for the adsorption of VOCs. Solid‐state NMR was applied to characterize host‐guest interactions and dynamics of chlorobenzene in two CPs with different topologies. While ligand dynamics were similar in both CPs, chlorobenzene was found to undergo more restricted dynamics in the CP with polycatenated topology because of the smaller free volume and stronger interactions.