Sodium carbonate-assisted synthesis of hierarchically porous single-crystalline nanosized zeolites

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

Microporous zeolites have proven to be of great importance in many chemical processes. Yet, they often suffer from diffusion limitations causing inefficient use of the available catalytically active sites. To address this problem, hierarchical zeolites have been developed, which extensively improve the catalytic performance. There is a multitude of recent literature describing synthesis of and catalysis with these hierarchical zeolites. This review attempts to organize and overview this literature (of the last 5 years), with emphasis on the most important advances with regard to synthesis and application of such zeolites. Special attention is paid to the most common and important 10- and 12-membered ring zeolites (MTT, TON, FER, MFI, MOR, FAU, and *BEA). In contrast to previous reviews, the research per zeolite topology is brought together and discussed here. This allows the reader to instantly find the best synthesis method in accordance to the desired zeolite properties. A summarizing graph is made available to enable the reader to select suitable synthesis procedures based on zeolite acidity and mesoporosity, the two most important tunable properties.

Highly dispersed Pt nanoparticles on ultrasmall EMT zeolite: A peroxidase-mimic nanoenzyme for detection of H2O2 or glucose

In past decade, Pt-based nanomaterials as peroxidase mimics have attracted much attention for H₂O₂ and glucose detection. However, easy aggregation of Pt nanoparticles (Pt NPs) greatly decreases their peroxidase-like activity. In this work, novel Pt/EMT nanocomposites were prepared by uniformly loading Pt NPs (5-8 nm) onto the support of ultrasmall EMT zeolite (15-20 nm), a kind of low-silica microporous aluminosilicate material. The hybrid Pt/EMT nanomaterials could be well dispersed in water to form a homogeneous suspension, and were then utilized as a superior peroxidase-like catalyst for oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂). The optimal catalyst of 2.6Pt/EMT nanocomposite exhibited excellent catalytic performance toward H₂O₂ and TMB than natural enzyme of horseradish peroxidase (HRP) by using a steady-state kinetic analysis based on the typical Michaelis-Menten kinetics theory. The peroxidase-like catalyst showed a promising activity in a wide pH and temperature range as well as the long-term stability. A facile and reliable colorimetric assay based on the peroxidase mimic of Pt/EMT nanocomposite was constructed for precise detection of H₂O₂ and glucose in a wide linear range, with low limits of detection of 1.1 μM and 13.2 μM, respectively. Due to high selectivity to glucose against other sugars on the catalyst, the method was demonstrated to accurately measure the concentration of glucose in real samples including human blood serum and fruit juices, indicating a potential application of the Pt/EMT nanocomposites as a robust peroxidase mimic and a reliable biosensor in the fields of clinical diagnosis, pharmaceutical, food research and so on.

Synthesis of highly-efficient photocatalyst for visible- light-driven hydrogen evolution by recycling of heavy metal ions in wastewater

Water pollution and energy crisis are two important research subjects awaited to solution. Herein, we propose a strategy of "turning scrap into wealth" to obtain the highly-efficient photocatalyst for hydrogen evolution by recycling of heavy metal ions in wastewater. The novel mesoporous zeolite Beta (mBeta) can be used as adsorbent to remove the heavy metal ions (i.e., Cd²⁺ and/or Zn²⁺) from wastewater due to its excellent adsorptive performance from the electrostatic affinity, ion-exchange ability and structural channels in zeolite. Subsequently, in-situ sulfuring of the Cd²⁺ or/and Zn²⁺ adsorbed mBeta was carried out to obtain highly-efficient photocatalysts. As expected, the sample CdS/ZnS-mBeta exhibited super photocatalytic activity and high stability under visible light irradiation. It is believed that the synergetic effect between CdS and ZnS nanoparticles are responsible for its good visible light absorption performance and the effective separation of photoelectrons and holes. Besides, the mBeta with high specific surface area can improve the dispersibility of sulfides, which would contribute to its high stability.

A novel protocol for the synthesis of pyrano[2,3-h]coumarins in the presence of Fe3O4@SiO2@(CH2)3OCO2Na as a magnetically heterogeneous catalyst

In this study, sodium carbonate functionalized silica coated-iron oxide nanoparticles (Fe₃O₄@SiO₂@(CH₂)₃OCO₂Na) were synthesized, characterized and applied as a heterogeneous basic nanocatalyst for the synthesis of pyrano[2,3-h]coumarins.