Modification of Zeolite Morphology via NH4F Etching for Catalytic Bioalcohol Conversion

Various commercial zeolites, including FER, MOR, ZSM-5, BEA, and FAU frameworks, were treated with NH₄F aqueous solutions to study the effects of fluoride etching on different zeolite frameworks. NH₄F-treated small-medium pore FER, MOR, and ZSM-5 samples showed much higher mesoporosities than the untreated ones without alteration of the structural compositions and acidic properties. On the other hand, the 12-membered ring zeolites BEA and FAU showed severe dissolution of the framework aluminosilicate structure after NH₄F etching due to the high accessibility of fluoride species into the framework structures. The effect of NH₄F concentration on the fluoride treatment of H-ZSM-5 zeolite was specifically studied. From the results, we observed that structural etching with 20 wt % NH₄F was optimal for fabricating open-pore H-ZSM-5 zeolite and resulted in a high mesoporosity with comparable relative crystallinity and acidity with respect to the untreated H-ZSM-5. The catalytic activities of the open-pore H-ZSM-5 were evaluated with acid-catalyzed methanol and bioethanol conversions. Remarkably, the hierarchical open-pore H-ZSM-5 zeolite fabricated via fluoride etching exhibited an enhanced catalytic performance in bioethanol conversion with >85 % conversion over 34 h TOS and a higher catalytic stability in methanol conversion than the parent H-ZSM-5 (~50 % of bioethanol conversion at 34 h TOS).     

Multipore Zeolites: Synthesis and Catalytic Applications

In the last few years, important efforts have been made to synthesize so‐called “multipore” zeolites, which contain channels of different dimensions within the same crystalline structure. This is a very attractive subject, since the presence of pores of different sizes would favor the preferential diffusion of reactants and products through those different channel systems, allowing unique catalytic activities for specific chemical processes. In this Review we describe the most attractive achievements in the rational synthesis of multipore zeolites, containing small to extra‐large pores, and the improvements reported for relevant chemical processes when these multipore zeolites have been used as catalysts.     

Tailoring Hierarchical Zeolites with Designed Cationic Surfactants and Their High Catalytic Performance

Three hierarchical porous zeolites (H‐*BEA, H‐MTW, and H‐*MRE) were successfully synthesized with the assistance of designed cationic surfactants under hydrothermal synthesis conditions. The as‐synthesized zeolite samples can be easily regulated by changing the number of long hydrophobic n ‐alkyl chains. Also, we investigated the relationship between the length of the surfactant and the formation of the microporous structure of the zeolite. Furthermore, the alkylation of benzene with propene was performed as a probe reaction to evaluate the catalytic performance of the synthesized hierarchical zeolites. The resulting materials were characterized by using a complementary combination of techniques, that is, X‐ray powder diffraction, N₂ adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy, Fourier transform IR spectroscopy, ²⁸Si and ²⁷Al MAS NMR spectroscopies, thermogravimetric analysis, and computer simulation. These analysis results indicated that quaternary ammonium surfactants acted as organic structure‐directing agents (OSDAs) in the formation of these hierarchical zeolite samples, whether the surfactant had long hydrophobic tail groups or not. The simulation results indicated that the organic molecules with no long hydrophobic chain could lead to the synthesis of zeolite through charge control, and the hydrophobic molecules with long hydrophobic chains could form zeolites through orbital control. These hierarchical zeolites showed improved catalytic activity towards the industrially relevant alkylation of benzene with propene compared with conventional zeolites with the same frameworks. More importantly, the success of using quaternary ammonium surfactants with no hydrophobic n ‐alkyl tail group in the synthesis of hierarchically structured mesoporous zeolites provides a new pathway for the synthesis of hierarchical porous materials by a soft‐templating method.     

二维沸石及其在大分子催化转化领域的研究进展

与三维结构沸石不同,二维沸石由于其更开放的孔道结构、更大的比表面积、更易暴露的酸性位点,在大分子和扩散限制催化领域显示了特殊优势。通过各种合成和后处理方法,能够调控二维沸石及其衍生材料的孔道种类、大小与分布,从而适用于不同的催化过程。本文综述了近年来二维沸石的合成与应用进展。     

Characterization and Wettability of ZnO Film Prepared by Chemical Etching Method

ZnO thin films were prepared by a chemical etching method and their wettability was investigated. The structure and surface composition structure were characterized by means of scanning electron microscopy, X-ray photoelectronic spectrometry(XPS), X-ray diffraction(XRD) and Raman spectrometry. These analyses reveal that the etched films were large-scale micro-nanohierarchical structures composed of a Zn core and a ZnO coating. Superhydrophobic surfaces with water contact angles of over 150o were obtained by n-octadecanethiol(ODT) modification. The XPS and Raman results indicate that ODT molecules were bound to the ZnO surface with the S head group by forming Zn-S bond.     

FSM-16系列改性中孔分子筛的制备及其对2-甲基吲哚和环己烯-2-酮的Michael加成催化作用

以十六烷基三甲基溴化铵（CTMAB）为模板剂,制备了改性中孔分子筛Zr-FSM-16、Al-FSM-16和Zr-Al-FSM-16,并用XRD、SEM、IR及BET等技术手段对分子筛进行表征。 在无溶剂条件下,考察了它们对2-甲基吲哚与环己烯-2-酮的Michael加成反应合成药物中间体3-（2-甲基-1H-吲哚-3-基）环己酮的催化活性。 实验结果表明,Al、Zr掺杂进入分子筛骨架中,导致分子筛孔道变大,而骨架结构没有明显改变;Al、Zr掺杂改性的FSM-16分子筛催化剂活性有了较大提高,其中Zr-FSM-16分子筛催化剂表现出较好的活性。 在催化剂用量7.5%、2-甲-基吲哚与环己烯-2-酮的摩尔比1.0∶1.1、反应温度80 ℃、反应时间120 min的较优条件下,2-甲基吲哚转化率达到75.4%。     

SSZ-35 and SSZ-44: Two Related Zeolites Containing Pores Circumscribed by Ten- and Eighteen-Membered Rings

Unusual one-dimensional pores circumscribed by 10- and 18-membered rings are a feature of the structures of two high-silica molecular sieves, SSZ-44 and SSZ-35. Structure solution and Rietveld refinement from synchrotron powder X-ray data reveal that the two materials are the pure end-member polymorphs of a new fault series and contain similar layerlike units (see picture). The SSZ-44 structure is formed by an AB stacking of the layers, whereas the SSZ-35 structure is formed through an ABC stacking of the layer units.     

Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis

The generation of a carbocation with an acid depends not only on the acid strength but also on the ability of the counteranion to stabilize the positive charge left behind. Here we report that despite their relatively weak acidity, zeolites are able to generate and stabilize medium‐size (molecular weight ≈300 Da) delocalized carbocations on their surface under mild reaction conditions, as it can be done by strong Brønsted or Lewis acids in solution. The zeolite thus acts as a soft macroanion, prolonging the lifetime of the carbocation sufficiently to perform multifunctionalization reactions with amides, thioamides, and phenols, with high yield and selectivity. Biological studies show that some of the products obtained here present significant inhibition activity against colon cancer cells, illustrating the new possibilities of zeolites to prepare complex organic molecules.     

In situ Nucleation-Growth Strategy for Controllable Heterogeneous Supramolecular Polymerization of Liquid Crystalline Block Copolymers and Their Hierarchical Assembly

The self-assembly morphologies of subunits are largely governed by thermodynamics, which plays a less important role in dimensional control. Particularly for one-dimensional assemblies from block copolymers (BCPs), the negligible energy difference between short and long ones imposes great challenges in length control. Herein, we report that by incorporating additional polymers to induce in situ nucleation and trigger the subsequent growth, controllable supramolecular polymerization driven by mesogenic ordering effect could be realized from liquid crystalline BCPs. The length of the resultant fibrillar supramolecular polymers (SP) is controlled by tuning the ratio between nucleating and growing components. Depending on the choice of BCPs, the SPs can be homopolymer-like, heterogeneous triblock, and even pentablock copolymer-like. More interestingly, with insoluble BCP as a nucleating component, amphiphilic SPs are fabricated, which can undergo spontaneous hierarchical assembly.     

Molybdenum Speciation and its Impact on Catalytic Activity during Methane Dehydroaromatization in Zeolite ZSM‐5 as Revealed by Operando X‐Ray Methods

Combined high‐resolution fluorescence detection X‐ray absorption near‐edge spectroscopy, X‐ray diffraction, and X‐ray emission spectroscopy have been employed under operando conditions to obtain detailed new insight into the nature of the Mo species on zeolite ZSM‐5 during methane dehydroaromatization. The results show that isolated Mo–oxo species present after calcination are converted by CH₄ into metastable MoC_xO_y species, which are primarily responsible for C₂H_x/C₃H_x formation. Further carburization leads to MoC₃ clusters, whose presence coincides with benzene formation. Both sintering of MoC₃ and accumulation of large hydrocarbons on the external surface, evidenced by fluorescence‐lifetime imaging microscopy, are principally responsible for the decrease in catalytic performance. These results show the importance of controlling Mo speciation to achieve the desired product formation, which has important implications for realizing the impact of CH₄ as a source for platform chemicals.     

Functionalized Silicas for Metal‐Free and Metal‐Based Catalytic Applications: A Review in Perspective of Green Chemistry

Heterogeneous catalysis plays a key role in promoting green chemistry through many routes. The functionalizable reactive silanols highlight silica as a beguiling support for the preparation of heterogeneous catalysts. Metal active sites anchored on functionalized silica (FS) usually demonstrate the better dispersion and stability due to their firm chemical interaction with FSs. Having certain functional groups in structure, FSs can act as the useful catalysts for few organic reactions even without the need of metal active sites which are termed as the covetous reusable organocatalysts. Magnetic FSs have laid the platform where the effortless recovery of catalysts is realized just using an external magnet, resulting in the simplified reaction procedure. Using FSs of multiple functional groups, we can envisage the shortened reaction pathway and, reduced chemical uses and chemical wastes. Unstable bio‐molecules like enzymes have been stabilized when they get chemically anchored on FSs. The resultant solid bio‐catalysts exhibited very good reusability in many catalytic reactions. Getting provoked from the green chemistry aspects and benefits of FS‐based catalysts, we confer the recent literature and progress focusing on the significance of FSs in heterogeneous catalysis. This review covers the preparative methods, types and catalytic applications of FSs. A special emphasis is given to the metal‐free FS catalysts, multiple FS‐based catalysts and magnetic FSs. Through this review, we presume that the contribution of FSs to green chemistry can be well understood. The future perspective of FSs and the improvements still required for implementing FS‐based catalysts in practical applications have been narrated at the end of this review.     

Chromogenic Polymers and Their Packaging Applications: A Review

Abstract

This review paper provides an overview of chromogenic polymers and their classifications, mechanisms, chemistry, synthesis procedures, and potential applications with a focus on packaging. Commonly and academically accepted classifications derived from chemical engineering, material science, and packaging science are used. Furthermore, recent progress and outputs aligned with chromogenic polymers for overcoming the common challenges are discussed. Finally, future prospects, market trends and academic investigations are described, including challenges related to chromogenic polymers.     

A Review of Bacteriochlorophyllides: Chemical Structures and Applications

Generally, bacteriochlorophyllides were responsible for the photosynthesis in bacteria. Seven types of bacteriochlorophyllides have been disclosed. Bacteriochlorophyllides a/b/g could be synthesized from divinyl chlorophyllide a. The other bacteriochlorophyllides c/d/e/f could be synthesized from chlorophyllide a. The chemical structure and synthetic route of bacteriochlorophyllides were summarized in this review. Furthermore, the potential applications of bacteriochlorophyllides in photosensitizers, immunosensors, influence on bacteriochlorophyll aggregation, dye-sensitized solar cell, heme synthesis and for light energy harvesting simulation were discussed.     

Colloid-Bound Catalysts for Ring-Opening Metathesis Polymerization: A Combination of Homogenous and Heterogeneous Properties

Tailor-made thiols allow a ruthenium-based catalyst for ring-opening metathesis polymerization (ROMP) to be tethered to bulk gold surfaces and to gold colloids (see picture). The functionalized gold colloids combine the properties of homogeneous and heterogeneous catalyst systems. Tethering of the catalyst leads to a pronounced increase in its catalytic activity.     

Ionic-Liquid-Based Nanofluids and Their Heat-Transfer Applications: A Comprehensive Review

Due to the improved thermophysical characteristics of ionic liquids (ILs), such as their strong ionic conductivity, negligible vapor pressure, and thermal stability at high temperatures, they are being looked at viable contender for future heat transfer fluids. Additionally, the dispersing nanoparticles can further improve the thermophysical characteristics and thermal performance of ionic liquids, which is one of the emerging research interests to increase the heat transfer rates of the thermal devices. The latest investigations about the utilization of ionic liquid nanofluids as a heat transfer fluid is summarized in this work. These summaries are broken down into three types: (a) the thermophysical parameters including thermal conductivity, viscosity, density, and specific heat of ionic liquids (base fluids), (b) the thermophysical properties like thermal conductivity, viscosity, density, and viscosity of ionic liquids based nanofluids (IL nanofluids), and (iii) utilization of IL nanofluids as a heat transfer fluid in the thermal devices. The techniques for measuring the thermophysical characteristics and the synthesis of IL nanofluids are also covered. The suggestions for potential future research directions for IL nanofluids are summarized.     

Understanding Mechanism and Designing Strategies for Sustainable Synthesis of Zeolites: A Personal Story

Zeolites with intricate micropores have been widely studied for a long time as an important class of porous materials in different areas of industrial processes such as gas adsorption and separation, ion exchange, and shape‐selective catalysis. However, their industrial syntheses are not sustainable, and normally require the presence of expensive organic templates and a large amount of solvents such as water. The presence of organic templates not only increases zeolite cost but also produces harmful gases during the removal of these templates by calcination, while the use of solvents significantly increases the amount of polluted water. This Personal Account briefly summarizes recent sustainable routes for the synthesis of zeolites in our group according to our understanding of the synthetic mechanism, and mainly focuses on the organotemplate‐free synthesis of zeolites in the presence of zeolite seeds, the design of environmentally friendly templates, and solvent‐free synthesis of zeolites.