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10 January 2021, Volume 42 Issue 1

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Content

Cover and Content of Chemical Journal of Chinese Universities Vol.42 No.1(2021)

2021, 42(1):  0. 

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Review

Progress in Direct Synthesis of High Silica Zeolite Y

WANG Juan, WANG Linying, ZHU Dali, CUI Wenhao, WANG Yifeng, TIAN Peng, LIU Zhongmin

2021, 42(1):  1-10.  doi:10.7503/cjcu20200419

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The synthesis of zeolite Y and its application in fluidized catalytic cracking could be taken as a milestone in the field of oil refining and petrochemical industry. It is well-known that the framework SiO₂/Al₂O₃ molar ratio（SAR） of zeolite Y determines its thermal/hydrothermal stability and catalytic properties. To improve the framework SAR of zeolite Y can effectively decrease acid sites density， enhance acid strength and thus ameliorate the thermal/hydrothermal stability and catalytic cracking performance. Currently， the high silica zeolite Y used in industry is prepared by complex post-synthesis treatment. Although direct synthesis is an ideal way to obtain high zeolite Y， it remains a challenging topic in the field of zeolite synthesis. Herein， we review the progress in direct synthesis of high silica zeolite Y， including the syntheses both in inorganic and organic systems. At last， we summarize the crystallization mechanism of zeolite Y.



Roles of Hydroxyl Radicals in Zeolite Synthesis

WANG Jianyu, ZHANG Qiang, YAN Wenfu, YU Jihong

2021, 42(1):  11-20.  doi:10.7503/cjcu20200476

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Zeolites have been widely utilized in chemical industry as the most important solid catalysts because of their tunable acidities and shape selective catalysis. Synthesis of zeolites is usually performed via hydrothermal crystallization in a strong basic medium. Hydroxide ions（OH^?） are considered to catalyze the depolymerization and polymerization of the silicate and aluminate species. Recently， it was found that the hydroxyl radicals（·OH） existed in the hydrothermal synthesis system. By using physical or chemical methods such as ultraviolet irradiation and Fenton’s reagent， ·OH radicals can be introduced into the zeolite synthesis system， which remarkably accelerated the zeolite crystallization and promoted the formation of zeolites with higher SiO₂/Al₂O₃ ratio. Density functional theory calculations demonstrated that ·OH radicals significantly facilitated the depolymerization of the aluminosilicate gel by breaking the Si—O—Si bonds and the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si—O—Si bonds， thus speeding up the nucleation and favoring Si incorporation into the zeolite frameworks. This review summarizes the recent progress in the application of ·OH radicals in the synthesis of zeolites， with an emphasis on the role and advantage of ·OH radicals in zeolite crystallization. The future perspective of the ·OH radical route for the synthesis of zeolites is pointed out.



Reconsideration of Crystallization Process for Aluminosilicate Zeolites

WU Qinming, WANG Yeqing, MENG Xiangju, XIAO Fengshou

2021, 42(1):  21-28.  doi:10.7503/cjcu20200201

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Despite great efforts have been performed for a long time since 1950s’， new achievements for zeolite synthesis in recent years give many examples to overstep the traditional theory for zeolite crystallization， in particular to the template effect， water role， zeolite building units， and crystal transformation in the aluminosilicate zeolites. In this review， authors systemically discuss the essence of the aforementioned factors. By investigation of template effect， it is suggested a new strategy for organotemplate-free synthesis of aluminosilicate zeolites； through understanding the role of water in the zeolite synthesis， it is designed solvent-free synthesis of zeolites； observed by crystal transformation of zeolites， it is proposed that both low to high framework density and high to low framework density could be realized.



Structural Stabilization， Modification and Catalytic Applications of Germanosilicates

JIAO Meichen, JIANG Jingang, XU Hao, WU Peng

2021, 42(1):  29-39.  doi:10.7503/cjcu20200382

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Germanosilicates with （extra）-large pores have shown significant potential in the bulky molecules-involved catalytic reactions. However， the Ge―O bonds are easily hydrolyzed even in humid environment and induced structural collapse， which restricts the practical application of germanosilicates. However， the weak Ge―O bonds also endow germanosilicates structural modifiable properties for possible construction of novel zeolite frameworks by partial or full removing framework Ge atoms to induce structural deconstruction and reconstruction. The review summarizes recent progresses achieved in field of germanosilicates， including structural stabilization of germanosilicates， structural modification of germanosilicates， and their promising catalytic applications. Last but not the least， future challenges in the field of germanosilicates are also proposed.



Recent Progresses on the Synthesis of Zeolites from the Industrial Solid Wastes

WANG Binyu, LI Li, LI Jing, JIN Keyan, ZHANG Shaoqing, ZHANG Jianan, YAN Wenfu

2021, 42(1):  40-59.  doi:10.7503/cjcu20200362

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Thisreview summarizes the latest progresses on the synthesis of zeolites using industrial solid wastes as raw materials. The industrial solid wastes include fly ash， perlite waste， coal gangue， spent FCC ca-talyst， lithium slag， bauxite residue， waste porcelain and glass. The zeolites crystallized from these industrial sold wastes are LTA， FAU， MFI， CHA， GIS， SOD， ANA and KFI. The key in the pretreatment of each solid waste was presented. Finally， the trend and challenges in the synthesis of zeolites using the industrial solid wasteswere discussed.



Recent Advances in the Synthesis of Mesoporous Zeolites by Post-synthetic Method， Supramolecular Self-assembly and Mesopore Generation Agent

LIU Qiyu, FAN Wei

2021, 42(1):  60-73.  doi:10.7503/cjcu20200687

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Hierarchical zeolites with intracrystalline mesopores exhibit the characteristic features of microporous zeolites and mesoporous materials， offering improved mass transport property and catalytic performance for zeolite materials. Development of mesoporous zeolites for catalysis， adsorption and separation has been significantly advanced in the past decades. In particular， several new synthesis strategies have been invented， which provided a wide range of flexibility and turnability to control the mesoporosity， composition and morpho-logy of mesoporous zeolites. In the short review， we focus on the recent advances in different synthesis strategies. Particular emphasis is given to the recently developed post-synthetic methods for the synthesis of low Si/Al ratio mesoporous zeolites， synthesis of mesoporous zeolites by supramolecular self-assembly and in situ synthesis of mesoporous zeolites using small organic molecules. The formation mechanisms associated with the synthesis approaches are discussed in order to provide insights into future development of mesoporous zeolites. At the end of this review， we discuss some critical challenges regarding the synthesis of mesoporous zeolites using the different synthesis strategies.



Controllable Synthesis， Diffusion Study and Catalysis of Hierarchical Zeolites

ZOU Run, DONG Xiao, JIAO Yilai, Carmine D'AGOSTINO, YAN Wenfu, FAN Xiaolei

2021, 42(1):  74-100.  doi:10.7503/cjcu20200461

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Hierarchical zeolites refer to zeolitic materials having bi-/multi-modal interconnective pores arranged in order of certain ranks， which improve the molecular diffusion within their frameworks， and hence the performance in their applications such as adsorption and heterogeneous catalysis. Hierarchical zeolites are commonly produced via the top-down post-synthetic treatments（such as dealumination and/or desilication） of pre-synthesized zeolites（i.e. the parent zeolites） and the bottom-up synthesis-by-design methods（such as soft/hard templating）. This review presents the recent advances（mainly post 2000） in the strategies of making hierarchical zeolites， with the emphasis on the top-down approaches due to their relatively high practicality. Since hierarchical zeolites are proposed to improve intracrystalline diffusion， experimental studies of guest molecules diffusion in hierarchical zeolites are also reviewed. Additionally， catalytic applications of hierarchical zeolites， in comparison with the conventional microporous pristine zeolites， are also commented to highlight the advantages of hierarchical zeolites to improve catalysis.



Extra-large Pore Zeolites： a Ten-year Updated Review

WEN Jiali, ZHANG Junhao, JIANG Jiuxing

2021, 42(1):  101-116.  doi:10.7503/cjcu20200410

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Zeolites are a vital type of crystalline material with well-defined channel structures and isolated catalytically active sites. However， their microporous nature hinders their applications in the transformation of bulky molecules. Ten years ago， Corma and coworkers provided a historical review of the synthesis， structure， and catalytic performance of extra-large pore（ELP） zeolites. This type of zeolite bridges the gap between traditional zeolites and ordered mesoporous materials. In the last decade， several new ELP zeolites， as well as novel methodologies for preparing them， have been reported. This review provides a renewed view of this topic.



Research Progress on Zeolite Layer Preparation via Oriented Seeded Growth

LIU Yi, LIU Yi

2021, 42(1):  117-132.  doi:10.7503/cjcu20200391

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In recent decades， fabrication of zeolite layers has attracted much research interest due to their potential applications in fields of separation， catalysis， sensing， and anticorrosion. Among them， uniformly oriented zeolite layers which benefit from reduced diffusion path lengths and decreased grain boundary defects have become the focus of researchers’ attention. In this review， major achievements made in oriented zeolite layer preparation were reviewed and commented with particular emphasis on the preparation of two-dimen- sional MFI nanosheets， deposition of b-oriented MFI seed monolayers， and microstructural manipulation of b-oriented MFI layers during secondary growth. Moreover， major problems hindering their bulk production were introduced and possible solutions were proposed. Finally， further development in this research field was highlighted.



Atomic Scale Structure of Beam Sensitive Materials

CHEN Xiao, SHEN Boyuan, XIONG Hao, WEI Fei

2021, 42(1):  133-147.  doi:10.7503/cjcu20200548

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Molecular sieves and metal organic framework （MOF） materials are widely used in the fields of catalysis， energy storage， drying， purification， and adsorption separation due to their unique pores and framework structures. The atomic scale characterization of their structures is significance for a deep understanding of their structure-activity relationships. However， their large pore structure and organic framework make them extremely sensitive to electron beam. The structure will be quickly destroyed and become amorphous in the conventional transmission electron microscope imaging mode， and the atomic arrangement information of the pores and framework cannot be obtained. The recently developed scanning transmission electron microscopy technology based on integrated differential phase contrast （iDPC-STEM） has shown obvious advantages in imaging of beam sensitive materials and light element components， making the characterization of porous framework materials and hydrocarbon pool species become possible. This article reviews our research group’s recent research on molecular sieve and MOF material atomic structure using this technology. The iDPC-STEM technology was applied to the ZSM-5 molecular sieve catalyst for methanol conversion to realize the imaging analysis of the atomic-level framework structure of the molecular sieve. In the MOF system， the coordination mode of the organic linker and the metal node in the MIL-101 framework was observed using this technology. On this basis， the benzene ring structure of the organic link and the metal node was analyzed， and the atomic-level surface， interface and defects and other local structural features of the MOF were observed. Finally， the application potential of iDPC-STEM technology in atomic scale imaging is summarized and prospected.



Progress in NMR Studies of Carbohydrates Conversion on Zeolites

QI Guodong, YE Xiaodong, XU Jun, DENG Feng

2021, 42(1):  148-164.  doi:10.7503/cjcu20200500

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Carbohydrates are important biomass feedstock which can be transformed to expected products by catalytic processes. Metal-containing zeolites with Lewis acidity have been found to exhibit excellent reactivity in conversion of carbohydrates. Understanding the nature of active sites and reaction mechanism is essential for the development of highly active catalyst towards carbohydrates conversion. Nuclear magnetic resonance（NMR） spectroscopy is a powerful tool to provide useful information on active site and reaction mechanism in zeolite catalysis. This review focuses on the recent progress of NMR studies of active centers， interactions between catalysts and reactants， reaction mechanisms and product distributions in catalytic conversion of carbohydrates on zeolites. Challenges and opportunities in this field are also discussed.



Study by Solid-state NMR Spectroscopy on the Acidity and Shape-selectivity of Zeolites

ZHAO Shufang, HUANG Jun

2021, 42(1):  165-178.  doi:10.7503/cjcu20200416

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Zeolites have the desired advantages of tunable acidity and shape selectivity for their outstanding performance in heterogeneous catalysis. This review focuses on the recent progress in the understanding of acidity and shape-selectivity in zeolites by solid-state nuclear magnetic resonance（ssNMR） spectroscopy. The number， strength， type， and synergistic effect of the acid sites in zeolites have been explored by ssNMR with/without probe molecules. Moreover， ssNMR investigations provide evidence of the shape-selectivity of zeolites by the direct observation of crucial intermediates in heterogeneous reactions. The synergy of the acidity and shape-selectivity helps the better design of the zeolites for better heterogeneous catalysis.



Applications of Materials Genome Engineering in Zeolites

CHEN Siqi, LI Li, LI Yi, YU Jihong

2021, 42(1):  179-187.  doi:10.7503/cjcu20200490

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Materials genome engineering integrates high-throughput computation， high-throughput experimentation and data technology to accelerate the design and development of new materials. As an important family of microporous materials， zeolites have been widely used in gas adsorption， separation， heterogeneous catalysis and ion exchange because of their excellent thermal stabilities， high specific surface areas， unique well- defined porous structures， and tunable framework compositions and acidities. To facilitate the development of novel zeolitic materials， materials genome engineering technology has recently been applied in many different areas in zeolite research. In this review， we will discuss about the recent progress in high-throughput computation， high-throughput experimentation and database of zeolites. Our perspectives on the future development of materials genome engineering of zeolites will be provided in the last section.



Applications of X-ray and Electron Crystallography in Structural Investigations of Zeolites

MA Chao, LIU Xiaona, NIE Chenyang, CHEN Lu, TIAN Peng, XU Hongyi, GUO Peng, LIU Zhongmin

2021, 42(1):  188-200.  doi:10.7503/cjcu20200406

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Zeolites， a class of crystalline microporous materials with unique channels or cavities， have excellent performance in adsorption， separation， and catalysis. In order to correlate the structure-property relationship， it is essential to determine the crystallographic structures of zeolite at the atomic level. In this review， a series of conventional and emerging techniques regarding X-ray crystallography and electron crystallography for characterizing the crystallographic structures of zeolites through real space and reciprocal space are introduced. Furthermore， 85 recently discovered novel zeolites are systemically summarized based on the structure determination approaches and their chemical compositions. Nine zeolites with different framework type codes（FTCs） are further highlighted due to their unique synthetic methodologies or structural features.



Progress of Zeolite Structural Analysis Based on Transmission Electron Microscopy

LING Yang, ZHANG Guanqun, MA Yanhang

2021, 42(1):  201-216.  doi:10.7503/cjcu20200415

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Transmission electron microscope has become a powerful tool to solve new zeolite structures， analyze structural defects and study active sites. It has two main functions， imaging and diffraction， including transmission/scanning transmission electron microscopy imaging， selected-area electron diffraction and three-dimensional electron diffraction. Multiple methods were usually combined for a thorough analysis. In recent years， there are breakthrough improvements on hardware of electron microscopes， especially the well- developed spherical aberration correctors and a variety of sensitive detectors， as well as developments of image processing methods. As a result， atomic level imaging of beam sensitive materials such as zeolites has been achievable. Moreover， in situ electron microscopy study of zeolite is also on the way， for a better understanding of zeolites growth and catalytic reaction. In this review we focus on the recent research progresses of zeolites studied by electron microscopy， including new structure analysis， handedness determination， metal@zeolites and so on.



Applications of Zeolite Catalysts in Chemical Industry

JIN Shaoqing, SUN Hongmin, YANG Weimin

2021, 42(1):  217-226.  doi:10.7503/cjcu20200418

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As a kind of important catalytic materials， zeolite has been widely used in chemical industry. In this paper， the applications of zeolite catalysts in the fields of petroleum refining， petrochemical， coal chemical， fine chemical and environmental chemical industries was systematically summarized. The significant role of zeolite catalysts in promoting technological progress and development of chemical industry was elucidated， and the future development of zeolite catalysts was prospected.



Article

Regulating the Acid Sites Distribution in ZSM-5 Zeolite and Its Catalytic Performance in the Conversion of Methanol to Olefins

GUO Shujia, WANG Sen, ZHANG Li, QIN Zhangfeng, WANG Pengfei, DONG Mei, WANG Jianguo, FAN Weibin

2021, 42(1):  227-238.  doi:10.7503/cjcu20200413

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The catalytic performance and reaction mechanism of ZSM-5 zeolite in the conversion of methanol to olefins（MTO） is closely related to the distribution of acid sites in framework. In this work， it was demonstrated that adding proper content of Na⁺ ions during synthesis can increase the proportion of acid sites in the intersection cavity of ZSM-5； the concentration of acid sites in the intersection cavity can promote the formation of higher polymethylbenzene（polyMBs） and the propagation of aromatic cycle， forming more ethene. In contrast， in the Na⁺ ions free synthesis system， more acid sites are distributed in the sinusoidal and straight channels of ZSM-5， which is more encouraging for the alkene cycle and conduces to producing more propene and higher alkenes（C₃₊）.



Review

Cooperative Catalysis of Adjacent Acid Sites in Zeolite HZSM-5

YU Xia, SONG Chenhai, GUO Xiangke, XUE Nianhua, DING Weiping

2021, 42(1):  239-247.  doi:10.7503/cjcu20200606

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Recent advances in cooperative catalysis from adjacent acid sites in zeolite HZSM-5 is summarized in this review. The cooperativity is from the Br?nsted acid site and the Lewis acid site as well as from adjacent Br?nsted acid sites. Kinds of characterization are described for molecular adsorption， activation and transformation together with catalysis performance. The theoretical calculation is also performed to prove the cooperative catalysis. The challenge of studying the new facile pathway of cooperative catalysis is also raised up， and accurate measuring the distance of two acid sites and quantifing the amount of adjacent acid sites are pursued as well.



Two-dimensional Nanosheets for Ultra-permeable Membrane-Based Gas Separation with High Efficiency

SONG Hongling, PENG Yuan, YANG Weishen

2021, 42(1):  248-267.  doi:10.7503/cjcu20200407

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Membrane-based separation is an advanced technology with significantly low energy consumption， and has enormous potential in industrial separation applications. However， commercial gas separation membranes are subjected to the trade-off between selectivity and permeability. Membranes constructed with two- dimensional（2D） nanosheets as building units hopefully break through this bottleneck. To date， the most representative 2D nanosheet membranes are graphene and its derivatives， 2D zeolites， layered double hydro-xides， 2D transition metal dichalcogenides， 2D covalent organic frameworks and metal-organic framework materials. In this review， the developments and progresses of these membrane materials in the field of gas separation will be introduced， presenting their merits and demerits in the practical separation process simultaneously， and the challenges and development prospects of the 2D nanosheet membranes for gas separation applications will be discussed.



Small Molecule Adsorption and Separation on Zeolites

LIU Shanshan, CHAI Yuchao, GUAN Naijia, LI Landong

2021, 42(1):  268-288.  doi:10.7503/cjcu20200458

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Adsorptive separation， the process of separating and purifying a gas mixture via the selective adsorption of one or more components on a porous solid adsorbent， is of great significance in industry. Zeolites， metal-organic framework materials and activated carbon are known as common solid adsorbents. Zeolites show significant advantages such as high specific surface area， high stability and low production cost to satisfy the requirements of highly efficient， energy-saving and environmentally friendly adsorptive separation processes. Therefore， zeolites have been established as most promising adsorbents for the separation of small molecules. In this review article， the existing materials， the fundamental mechanisms and the evaluation methods in adsorptive separation are firstly outlined. The applications of zeolites in air separation， hydrocarbon separation， carbon dioxide capture， aromatic sulfide removal， carbon monoxide adsorption， nitrogen oxides adsorption， hydrogen storage and hydrogen isotope separation are then summarized. Finally， the current status of small molecule separation based on zeolite membranes are briefly discussed. The relationship between the adsorption performance and the topology， framework composition， and modification methods of zeolites are focused， and the future research prospects are discussed on the basis of current achievements.



Recent Advances on Zeolite Membrane Reactors

ZHANG Yuting, ZHANG Chun, GU Xuehong

2021, 42(1):  289-298.  doi:10.7503/cjcu20200517

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Zeolite membranes have been widely attractive in gas and liquid separations between small molecules for their advantages of well-defined sub-nanometer pores， good tolerance against high temperature， high pressure and organic solvents. Zeolite membrane reactor that integrates zeolite membrane and catalyst into one unit， where the reaction and component diffusion occur simultaneously， can shift the equilibrium so as to intensify the reaction process. In this review， we give a brief introduction on the significant progress of different kinds of zeolite membrane reactors in catalytic reactions in the last decade. Furthermore， the development trend of zeolite membrane reactors in future are discussed.



Recent Progress on Photoluminescent Zeolite-based Composite Materials

WANG Bolun, ZONG Siyu, LI Jiyang

2021, 42(1):  299-310.  doi:10.7503/cjcu20200400

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This review summarizes the recent progress on photoluminescent zeolite-based composite mate- rials， including the preparation and assembly strategies of composite materials based on encapsulating guests（e.g. rare earth metals， metal clusters， quantum dots/carbon dots and other luminescent emitters）， photoluminescent properties and potential applications， as well as the possible host-guest interactions such as quantum confinement， intermolecular forces， energy/electron transfer. Finally， the further development and challenges of such composite materials are discussed.



Interaction of Zeolites and Proteins and Its Biomedical Function

YU Lisha, LI Dan, XIAO Liping, FAN Jie

2021, 42(1):  311-320.  doi:10.7503/cjcu20200637

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Zeolite is considered as a new type of biomaterial in medical treatment， due to its low toxicity and good biocompatibility. This article reviews the interaction between zeolites and proteins. Zeolites have specific binding or reaction with proteins due to their ion exchange capacity， surface properties， and controllable pore structure， which affects the performance and behavior of proteins. The application of zeolites in the biomedical field is mainly discussed， including their uses as antimicrobial agents and hemostatic materials； the article analyzes the unique advantages of zeolites in the medical field， especially in the field of hemostatic applications， and finally summarizes and looks forward to the challenges and development prospects.