Metal-free boron-containing materials are growing to
be promising
choices in oxidative dehydrogenation (ODH) of light alkanes to alkenes,
while it remains unclear how the boron content and the second element
that constitutes the scaffold to accommodate B in the materials may
influence their catalytic activity. Herein, by means of the density
functional theory study of nanosized boron carbide, we studied the
mechanisms of ODH of propane (ODHP) catalyzed by three types of boron
carbides, B13C2, B4C, and h-BC, which
differ from each other in their B contents and their chemical topologies.
The influence of hydroxyl coverage on the surface was also evaluated
to address the structure–catalytic activity relationship in
the ODHP reaction. The calculations show that (1) the B element content
and the hydroxyl groups could regulate the electronic structure and
significantly increase the highest occupied molecular orbital (HOMO)
energy to promote chemical reactivity. (2) Boron carbide with higher
coverage of hydroxyl groups on the surface (B
13
C
2
-H and B
4
C-H) exhibits
higher activity for catalyzing ODHP reaction owing to the enhanced
nucleophilicity, which is further confirmed by the noncovalent interaction
(NCI) analysis. (3) The reactivity of the catalyst is positively correlated
with the B content, and the ODHP catalyzed by B13C2 is kinetically more favorable than that by B4C
and h-BC. This study is expected to enrich our understanding of the
structure–activity relationship of boron-based catalysts in
the ODH system and benefit the optimization of the catalytic systems.