Assembly of Silicalite-1 Crystals Like Toy Lego Bricks into One-, Two-, and Three-Dimensional Architectures for Enhancing Its Adsorptive Separation and Catalytic Performances

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.

Strategies to control zeolite particle morphology

Methods to synthesize zeolites with different crystal habits and assemble zeolite crystals into specific structures are reviewed for the rational design of zeolite particle morphologies.

CO2 capture and storage: A way forward for sustainable environment

The quest for a sustainable environment and combating global warming, carbon capture, and storage (CCS) has become the primary resort. A complete shift from non-renewable resources to renewable resources is currently impossible due to its major share in energy generation; making CCS an imperative need of the time. This study, therefore, aims to examine the reckoning of carbon dioxide (CO₂), measurement methods, and its efficient capture and storage technologies with an ambition to combat global warming and achieve environmental sustainability. Conventionally, physical, geological and biological proxies are used to measure CO₂. The recent methods for CO₂ analyses are spectrometry, electrochemical gas sensors, and gas chromatography. Various procedures such as pre, post, and oxyfuel combustion, and use of algae, biochar, and charcoal are the promising ways for CO₂ sequestration. However, the efficient implementation of CCS lies in the application of nanotechnology that, in the future, could provide a better condition for the environment and economic outlooks. The captured carbon can be stored in the earth crust for trillions of years, but its leakage during storage can raise many issues including its emissions in the atmosphere and soil acidification. Therefore, global and collective efforts are required to explore, optimize and implement new techniques for CCS to achieve high environmental sustainability and combat the issues of global warming.