Comprehensive Understanding of the Eco-Friendly Synthesis of Zeolites: Needs of 21st Century Sustainable Chemical Industries

Synthesis and Crystallization Mechanism for SAPO-34 Zeolite Derived from Magadiite

In this work, we explored the hydrothermal synthesize and crystallization process of SAPO-34 zeolites from two-dimensional layered silicate magadiite by using tetraethylammonium hydroxide (TEAOH) as a templating agent. Comprehensive characterization was conducted by XRD, SEM, FTIR, Raman, and BET. Time-resolved PXRD analysis revealed that SAPO-34 zeolite exhibited a steep growth curve when the crystallization time was 30 h, and the crystallinity reached 98.65 % at 48 h. Specifically, the disruption of the magadiite layer exposed charged silanol groups on the surface, fostering an affinity for AlO4 and PO4 species, thereby initiating the nucleation process. Under the guidance of TEAOH, these nucleation sites transformed into SAPO-34 nuclei, gradually advancing towards crystallization. FTIR and Raman analyses affirmed the presence of 6Rs, followed by D6R and 4Rs SBUs, along with the characteristic CHA structure. Combined with 29Si NMR established that disaggregated silicate minerals served as zeolite synthesis "seeds", enhancing nucleation sites and overall crystallization efficiency.

Intelligent micro/nanorobots based on biotemplates

Intelligent micro/nanorobots based on natural materials as biotemplates are considered to be some of the most promising robots in the future in the microscopic field. Due to the advantages of biotemplates such as unique structure, abundant resources, environmental friendliness, easy removal, low price, easy access, and renewability, intelligent micro/nanorobots based on biotemplates can be endowed with both excellent biomaterial activity and unique structural morphology through biotemplates themselves and specific functions through artificial micro/nanotechnology. Thus, intelligent micro/nanorobots show excellent application potential in various fields from biomedical applications to environmental remediation. In this review, we introduce the advantages of using natural biological materials as biotemplates to build intelligent micro/nanorobots, and then, classify the micro/nanorobots according to different types of biotemplates, systematically detail their preparation strategies and summarize their application prospects. Finally, in order to further advance the development of intelligent micro/nanorobots, we discuss the current challenges and future prospects of biotemplates. Intelligent micro/nanorobots based on biotemplates are a perfect combination of natural biotemplates and micro/nanotechnology, which is an important trend for the future development of micro/nanorobots. We hope this review can provide useful references for developing more intelligent, efficient and safe micro/nanorobots in the future.

Accelerated Synthesis of Nanolayered MWW Zeolite by Interzeolite Transformation

Hierarchical zeolites can offer substantial benefits over bulk zeolites in catalysis. A drawback towards practical implementation is their lengthy synthesis, often requiring complex organic templates. This work describes an accelerated synthesis of nanolayered MWW zeolite based on the combination of interzeolite transformation (IZT) with a dual-templating strategy. FAU zeolite, hexamethyleneimine (HMI), and cetyltrimethylammonium bromide (CTAB) were respectively employed as Al source and primary zeolite, structure directing agent, and exfoliating agent. This approach allowed to reduce the synthesis of nanolayered MWW to 48 h, which is a considerable advance over the state of the art. Tracking structural, textural, morphological, and chemical properties during crystallization showed that 4-membered-ring (4MR) units derived from the FAU precursor are involved in the faster formation of MWW in comparison to a synthesis procedure from amorphous precursor. CTAB restricts the growth of the zeolite in the c-direction, resulting in nanolayered MWW. Moreover, we show that this approach can speed up the synthesis of nanolayered FER. The merits of nanolayered MWW zeolites are demonstrated in terms of improved catalytic performance in the Diels-Alder cycloaddition of 2,5-dimethylfuran and ethylene to p-xylene compared to bulk reference MWW sample.