Assembly
of Silicalite‑1 Crystals Like Toy
Lego Bricks into One‑, Two‑, and Three-Dimensional Architectures
for Enhancing Its Adsorptive Separation and Catalytic Performances
posted on 2021-11-26, 19:03authored byShiying Li, Hu Shi, Sen Wang, Zhikai Li, Pengfei Wang, Xingchen Liu, Yanhong Quan, Mei Dong, Jianguo Wang, Weibin Fan
Many
researchers have contributed to the assembly of zeolitic nanosheets
and nanocrystallites into three-dimensional (3D) networks as it can
remarkably improve the catalytic and/or adsorptive performances of
zeolites. However, the applications of these synthesized materials
are seriously limited because of low hydrothermal stability. A highly
interesting strategy, but a great challenge, is the alignment of well-crystallized
zeolite crystals into desirable architectures. Here, well-crystallized
silicalite-1 crystals are assembled like toy Lego bricks into one-dimensional
(1D), two-dimensional (2D), and three-dimensional (3D) architectures,
and the assembly mechanism is investigated by combining elaborate
experiments, in situ spectroscopy, and theoretical calculations. A
1D architecture was formed by stacking crystals along the b axis with the assistance of ethanol that is selectively
adsorbed on (100) and (001) crystal facets. Such adsorption increases
the condensation energy barriers along a and c axes, but facilitates the condensation between (010) facets.
The assembly of the crystals into well-arrayed 2D architectures is
achieved using both ethanol and benzaldehyde because of their preferable
adsorption on the (001) facet. When an amphiphilic copolymer (P123)
was further added in the gel along with the substitution of ethanol
by 1-propanol, a 3D network was fabricated by the agglomeration and
self-pillaring of the 2D Lego bricks possibly with P123 aggregates
as the substrate matrix. Excitingly, upon alignment of crystals into
2D architectures, the adsorptive selectivity of 1-butanol (2 wt %)
to water of silicalite-1 increases by 45.3 times, while into 3D networks,
the catalytic activity for the Beckmann rearrangement of cyclohexanone
oxime elevates by 79% along with a great enhancement of catalytic
stability.