Kinetic Monte Carlo Simulation of the Synthesis of
Periodic Mesoporous Silicas SBA‑2 and STAC-1: Generation of
Realistic Atomistic Models
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Abstract
SBA-2 and STAC-1 are two related periodic mesoporous silicas (PMSs)
that have regular networks of spherical, interconnected pores; the
pores are similar in the two materials but the networks differ in
their symmetry. The nature of the interconnected network of pores
in these materials gives rise to interesting properties related to
their potential use in separation processes. In this work, we extend
a kinetic Monte Carlo (kMC) technique, originally derived for MCM-41,
a simpler PMS, and apply it to mimic the condensation, aggregation,
deformation, and calcination stages of the synthesis of SBA-2 and
STAC-1. Our simulated synthesis results suggest that the pores are
connected through windows formed during micelle aggregation because
of the close packing of the spherical micelles and the presence of
water molecules at the silica–micelle interface. The simulated
materials were validated by comparing properties such as unit cell
size, pore size, pore shape, and wall density to results from experimental
X-ray diffraction (XRD), transmission electron microscopy (TEM), density
measurements, and <sup>29</sup>Si NMR. Quantitative agreement between
simulated and experimental nitrogen isotherms was achieved demonstrating
the realism of the pore models obtained by the kMC simulations. Our
results highlight the importance of a realistic, rough pore surface
for the prediction of adsorption at low pressures in these materials