Solvation Structure of Surface-Supported Amine Fragments: A Molecular
Dynamics Study
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Abstract
Amine-grafted
silica gel is an efficient heterogeneous catalyst for the Knoevenagel
condensation and draws much attention in green chemistry for applications
like heavy metal adsorption and CO<sub>2</sub> fixation. Despite its
successful usage in diverse areas, fundamental questions remain on
how the silica substrate affects the local chemical environment of
the tethered amines. In this work, we use all-atom molecular dynamics
simulation to investigate the solvation structures of two primary
amines tethered onto a silica surface at different pHs of aqueous
solutions. The atomic density profiles in the solvation shell are
analyzed with a spherical harmonics expansion method for both isolated
and silica-supported amines in different aqueous environments. The
simulation results provide direct evidence for the strong influence
of the silica surface on the hydration structure that is often ignored
in the theoretical analysis of surface reactions. The surface effect
becomes less prominent on the tethered amine as the alkyl chain length
increases