Understanding
solid-fluid interactions within porous materials is critical for their
efficient utilisation across chemical reaction and separation processes.
However, detailed characterisation of interfacial phenomena within such systems
is hampered by their optically opaque nature. Motivated by the need to bridge
this capability gap, we detail here the application of low magnetic field 2D <sup>1</sup>H
nuclear spin relaxation measurements as a non-invasive probe of sorbate/sorbent
interactions, exploring the relaxation characteristics exhibited by liquid
adsorbates confined to a model mesoporous silica. For the first time, we demonstrate
the capacity of such measurements to distinguish functional group-specific
relaxation phenomena across a diverse range of protic adsorbates of wide importance
as solvents, reagents, and hydrogen carriers, with distinct relaxation
environments assigned to the alkyl and hydroxyl moieties of the confined liquids.
Uniquely, this relaxation behaviour is shown to correlate with adsorbate acidity,
with the observed relationship rationalised on the basis of surface-adsorbate
proton exchange dynamics.
Low-Field Functional Group Resolved Nuclear Spin Relaxation in Mesoporous Silica
