As a kind of three-dimensional molecule with permanent cavity, organic molecular cages (OMCs) have gained intensive attention of the researchers in recent years, mainly due to their significant role in supramolecular chemistry as host molecules. Firstly, most of OMCs were synthesized via irreversible bond formation. However, the irreversible nature of these reactions usually caused serious problems, such as quite complex purification process and low overall yields. As an alternative approach, dynamic covalent chemistry has shown its power in the construction of OMCs from simple precursors with high yields. In recent years, by using various dynamic covalent reactions, a series of OMCs have been successfully synthesized in large scale, which facilitates their interesting applications. It is found that OMCs can not only show great potential applications in the fields of molecular recognition and molecular flask, but also form crystalline porous materials through self-assembly, which have shown interesting applications in gas absorption and separation. In this review, we will summarize the research progress of OMCs, highlight the synthesis of these OMCs by using various dynamic covalent reactions and also discuss their interesting applications in different areas. Perspectives of OMCs are also mentioned, regarding to their remaining challenging issues.

Contents
1 Introduction
2 Synthesis of organic molecular cages
2.1 Boronic acid condensation
2.2 Imine condensation reaction
2.3 Alkyne/alkene metathesis
2.4 Other dynamic covalent reactions
3 Applications of organic molecular cages
3.1 Molecular recognition
3.2 Molecular flask
3.3 Porous materials
4 Conclusion and outlook

Cucurbit[n] urils (CB[n] s), as a kind of rapidly developing supramolecular hosts, have been attracting more and more attentions. With their rigid structures, hydrophobic cavities and electronegative carbonyl groups on the portals, CB[n] s show their unique recognition properties——high selectivity and high binding affinity toward organic cations. In the past decade, CB[n] s have been utilized not only in basic recognition research but also in the construction of complicated three-dimensional materials and even in drug delivery systems. Besides, CB[n] s have been creatively used to control the reaction process and have obtained numerous successes. Herein, this review mainly describes the use of cucurbiturils as supramolecular nanoreactors/catalysts to accelerate or control the reaction process in thermal reactions as well as photoreactions. Moreover, the inhibition effect on guest's activity caused by the encapsulation inside cucurbiturils is also discussed.

Contents
1 Introduction
2 CB[n]s used as supramolecular nanoreactors/catalysts in thermal reactions
2.1 [3+2] cycloaddition reactions
2.2 Solvolysis reactions
2.3 Oxidation reactions
2.4 Other thermal reactions
3 [n]s used as supramolecular nanoreactors/catalysts in photoreactions
3.1 [2+2] cycloaddition reactions
3.2 [4+4] cycloaddition reactions
3.3 Other photoreactions
4 CB[n]s used as inhibiting agents
4.1 Protective agents
4.2 Toxicity inhibitors
4.3 Reaction inhibitors
5 Conclusion

Particle film (particulate film or granular film) based emulsions have attracted great attention because they are widely used in oil, paper, food, cosmetics, pharmaceuticals and other fields. This paper summarizes the characteristics of film-forming particles on the oil-water interface such as density, size and wettability, and expounds the adsorption and diffusion of particles on the oil-water interface. The structures of particle film are highlighted, including the distribution and orientation of particles perpendicular to the interface, the arrangement of particles on the oil-water interface and the spatial structures of film. The influencing factors of the state of particles on the oil-water interface as well as the particle film structures are summed up, then the nature of them is analyzed from the aspects of energy and mechanics. The mechanism of particle film stabilizing emulsion is elucidated from the structures of particle film and the interfacial viscoelasticity. The particle film hinders the collision and coalescence between the dispersed droplets, which is the basis of stable emulsions. Meanwhile, strengthened interfacial viscoelasticity makes sure the particle film will not easily collapse during dispersed droplets' movement, collision and flocculation. The mechanism of solid particles stabilizing emulsion as emulsifiers provides a theoretical basis for not only the preparation of stable emulsions but also the demulsification of emulsions, which is of important realistic significance. At last, we propose prospects of future development and possible solutions of the study on the mechanism of particle film stabilizing emulsion.

Contents
1 Introduction
2 The formation of particle film
2.1 The sources of particles
2.2 The characteristics of particles
2.3 The adsorption and diffusion of particles on the oil-water interface
3 The structures of particle film
3.1 Distribution and orientation of particles perpendicular to the interface
3.2 Arrangement of particles on the oil-water interface
3.3 Spatial structures of particle film
4 The mechanism of particle film stabilizing emulsion
4.1 The impact of particle film’s structures on emulsion stability
4.2 The impact of interface viscoelasticity on emulsion stability
5 Conclusion

The vigorous increase of the frequency of water pollution has become serious bottlenecks constraining national economy and modern industry development. Therefore, the research on the control and treatment of water contaminants is of great significance and urgency. Zeolitic imidazolate frameworks (ZIFs), as a product of chemical and material science that have been rapidly developing in recent years, have received extensive attention around the world and have been applied to waste water treatment owing to their stable structure, high surface area and excellent performance. Taking the ZIF-8 as the representative, this paper reviews the research and development on the application of ZIFs to remove water contaminants. The performance of the ZIFs in removal of water contaminants as the adsorbent and photocatalyst is introduced systematically, the factors influencing water contaminants removal by ZIFs are summed up. Moreover, it has carried on the forecast to later period's research. The objective of this paper is to provide theoretical reference for the practical application of ZIFs to the treatment of real waste water.

Contents
1 Introduction
2 Effect of ZIFs on the removal of water contaminants
2.1 Removal efficiency of ZIFs as adsorbent for water contaminants
2.2 Removal efficiency of water contaminants by ZIFs used as photocatalyst
3 Factors influencing removal of water contaminants by ZIFs
3.1 Preparation of ZIFs for the removal of water contaminants
3.2 Environmental impact of ZIFs on the removal of water contaminants
4 The mechanism of water contaminants removal by ZIFs
4.1 ZIFs as adsorbent
4.2 ZIFs as photocatalyst
5 Conclusions

Propylene oxide (PO), as the third largest propene derivative ranking behind polypropylene and acrylonitrile, is widely used in light industry, pharmaceutical and textile industries. Compared with traditional chlorohydrin and hydroperoxide processes, direct propene epoxidation with hydrogen and oxygen to synthesize PO has the advantages of being green, simple and profitable. It is therefore a current worldwide research hotspot. Herein, recent progress is reviewed with the purpose of solving remaining problems such as poor stability and low activity. Moreover, the effect of surface and structural properties of Ti-containing supports together with the morphologic and electronic effect of gold nanoparticles on catalytic activity and stability are introduced. The reaction mechanism and deactivation mechanism are further discussed. The influences of additives such as Cs, Ag, Pd, Pt, Ge, surface alkylation, ionic liquid and nitrogen doping on catalytic performance are summarized. The existing problems in direct propene epoxidation with H₂ and O₂ are also analyzed. In the end, possible solutions and directions from the aspects of selecting supports and improving catalytic performance are remarked.

Contents
1 Introduction
2 Effect of support properties
2.1 Different Ti-containing supports
2.2 Hydrophobicity of supports
2.3 Si/Ti molar ratio
3 Effect of properties of gold nanoparticles
3.1 Gold nanoparticle size
3.2 Gold active sites
3.3 Gold deposition location
4 Effect of promoters
5 Conclusion

Superhydrophobic materials have extensive application prospects in our daily life and industrial fields due to their unique self-cleaning characteristic. At present, the diversity of superhydrophobic materials properties has attracted more attention in basic research and practical application with the maturity on the research of single functional superhydrophobic materials, such as transparency, wear durability and wettability conversion, etc. Transparent superhydrophobic coatings possess good transparency, besides the general performance of the superhydrophobic coatings; enhance the wear resistance of superhydrophobic materials has a very important significance in practical application; and the wettability conversion can extend the application of superhydrophobic surfaces in oil-water separation and other aspects. The research of superhydrophobic materials is plentiful, but it still can not meet the demand for superhydrophobic surface functionality. Therefore, it's always worth researching on the superhydrophobic coating with functionalization. Herein, we review the research progress of the transparency, wear durability, wettability switch, separation of mixture and other aspects on superhydrophobic materials. The future research focus and development direction about superhydrophobic materials fields are pointed out.

Contents
1 Introduction
2 Transparent superhydrophobic surfaces
2.1 The research of transparent superhydrophobic materials
2.2 Control for the transparence of superhydrophobic surface
3 Wear resistance and durability of superhydrophobic surfaces
3.1 Test methods for wear resistance and durability of superhydrophobic surface
3.2 The way to improve the wear resistance and durability of superhydrophobic surface
4 Separation of mixture
4.1 Oil-water separation
4.2 Membrane distilation
4.3 Drug release
5 Wettability transformation of superhydrophobic surfaces
5.1 Single factor stimuli-responsive surfaces
5.2 Multifactors responsive switchable surfaces
6 Research of other functional superhydrophobic surfaces
7 Existing problems
8 Outlook

Mg(NH₂)₂-2LiH system possesses a higher reversible hydrogen storage capacity and favorable thermodynamics, consequently being regarded as one of the most promising hydrogen storage materials. However, a temperature above 200℃ is needed to obtain quick de-/hydrogenation because of a rather high kinetic barrier. As a result, numerous investigations have been attempted to adjust the hydrogen storage thermodynamics and kinetics properties. Starting from the three aspects of material composites, nanocrystallization and modification by doping, the progress in the hydrogen storage thermodynamics and kinetics is systematically summarized in this review. The challenges and countermeasures are illustrated, and the direction to further enhancing the hydrogen storage properties of the Mg(NH₂)₂-2LiH system is also pointed out.

Contents
1 Introduction
2 Compositional manipulation of the Li-Mg-N-H system
3 Nanosized Li-Mg-N-H system
4 Modification by doping
4.1 The effect of transition metals and their compounds
4.2 The effect of carbon-based materials
4.3 The effect of metal borohydrides
4.4 The effect of alkali metal-based compounds
4.5 The effect of other dopants
5 Conclusion

Ring-opening reactions of oxetanes include nucleophilic, electrophilic, radical, acid-catalyzed, and reductive ring-opening modes. Ring-opening reactions of unsymmetric oxetanes and their regioselectivity are summarized and reviewed. The regioselectivity of these ring-opening reactions is mainly influenced by steric and electronic effects. Nucleophilic ring-opening reactions of unsymmetric oxetanes with various nucleophiles are major ring opening reactions of oxetanes. Strong nucleophiles mainly attack the less substituted oxygen-adjacent carbon atom of unsymmetric oxetanes (steric effect control). They attack on the β-carbon atom of the vinyl group in 2-vinyloxetanes, undergoing an S_N2' ring-opening reaction. Only in the presence of acids, unsymmetric oxetanes can be attacked on their more substituted oxygen-adjacent carbon atom with weak nucleophiles such as O-nucleophiles or halides (electronic effect control). However, electrophilic ring-enlargement reactions, radical ring-opening coupling reactions, Lewis acid-catalyzed ring-opening reactions and Pd-catalyzed hydrogenolysis reactions take place at sterically hindered oxygen-adjacent carbon atom of unsymmtric oxetanes. The current summarized results provide important and useful imformation for chemists who apply ring-opening reactions of oxetanes and promote the application of ring-opening reactions of oxetanes.

Contents
1 Nucleophilc ring-opening reactions
1.1 Nuclephiles in group C
1.2 Nucleophiles in group N
1.3 Nucleophiles in group O
1.4 Halogen nucleophiles
1.5 Hydride nucleophiles
2 Electrophilic ring-enlargement reactions
3 Radical ring-opening coupling reactions
4 Miscellaneous ring-opening reactions
4.1 Strong base-promoted ring-opening reactions
4.2 Lewis acid-catalyzed ring-opening reactions
4.3 Acid-catalyzed ring-opening and ring enlargement reactions
4.4 Reductive ring-opening reactions
5 Conclusions

Thermally activated delayed fluorescence (TADF) materials, capable of efficient reverse intersystem crossing (RISC) from the lowest triplet excited state (T₁) to the lowest singlet excited state (S₁) to use triplet excitons for photoluminescence with theoretically 100% exciton harvesting in emission, have attracted great attention in recent research of organic electronics, especially in the field of organic light emitting diodes (OLEDs). The singlet-triplet energy splitting (ΔE_ST) between S₁ and T₁ should be low, which is a key point to facilitate the RISC process in tuning triplet excitons to singlet excitons for delayed fluorescence emission. With the significant advantages of convenient molecular design, easy preparation, rich optoelectronic properties, and excellent device performance, TADF materials with donor-acceptor (D-A) molecular structures are of central importance in the current development of high-performance TADF molecules. In this article, we review the basic molecular design principles of the D-A type TADF materials and summarize their molecular structure characteristics, optoelectronic properties and device application performance in the latest research progress, according to the varied types of acceptor building blocks. Finally, the existing problems, future opportunities and key challenges of TADF materials with D-A architectures are discussed to give a full view of this kind of new organic optoelectronic materials.

Contents
1 Introduction
2 Basic principles of TADF materials and applications
3 Molecular design of D-A type TADF materials
4 Intramolecular D-A type TADF molecules
4.1 Cyano-based TADF molecules
4.2 Nitrogen heterocycle-based TADF molecules
4.3 Diphenyl sulfoxide-based TADF molecules
4.4 Diphenyl ketone-based TADF molecules
4.5 10H-Phenoxaborin-based TADF molecules
5 Intermolecular D-A type TADF materials
6 D-A type TADF polymers
7 Conclusion

In recent years, electrochemical biosensor technology has received more and more attention by the virtue of its unique detection, analysis methods and the potential applications in clinical diagnostic. Early detection of cancer biomarkers could diagnose specific diseases timely, and provide treatment for the disease before it develops into its later period to thereby increase survival rate of patients. Furthermore, biomarkers can be used to determine the recurrence of the disease and evaluate the follow-up period after chemotherapy, radiotherapy and surgery. In this paper, we mainly discuss the existing equipment and methods of the cancer biomarkers detection, and briefly comment on the advantages and disadvantages of these methods. In addition, we also introduce the development of in vitro diagnostic devices and the characteristics of electrochemical biosensor technology, and present the major biomarkers in early cancer stage. Furthermore, we also focus on the detection of clinical targeted biomarkers by electrochemical biological sensing technology. The future research direction and development trend of electrochemical biological sensing technology are prospected. According to present researches, electrochemical biological sensing technology possesses great application potential in the areas of in vitro diagnostic and detection of clinical cancer biomarkers. With these features, in vitro diagnostic devices become unique and of great significance, and electrochemical biological sensing technology is expected to be quite important in the field of biology, medicine, environment, and so on.

Contents
1 Introduction
2 Biosensor technology
3 Application of electrochemical biosensor technology
3.1 Electrochemical DNA biosensor
3.2 Electrochemical immunosensor
3.3 Circulating tumor cells (CTCs) electrochemical biosensor
3.4 Glucose electrochemical biosensor
3.5 Hydrogen peroxide electrochemical biosensor
3.6 Electrochemical biosensor for small molecules of metabolite detection
4 Conclusion

Mercury emission reduction has become a global consensus due to the physiochemical properties of mercury and its side effects on humans. Adsorption is considered as a potential Hg²⁺ ions removal method. Chitosan is a natural Hg²⁺ ions adsorbent, and its Hg²⁺ ions adsorption capacity and efficiency can be improved by preparation of modified derivatives from physiochemical methods. Hg²⁺ ions adsorption by chitosan and its derivatives is now assumed to occur through several single or mixed interactions:the amino group (-NH₂) and hydroxyl (-OH), which adsorb Hg²⁺ ions mainly through chelate, ion exchange or electrostatic force. The protonated amino group of chitosan and C=N group (Schiff base) of its derivatives may are the main selective functional groups responsible for Hg²⁺ ions adsorption. In this study, we review the research progress of Hg²⁺ ions removal by chitosan and its composites in the field of water treatment, and introduce the means of chitosan physiochemical modification (e.g. freeze drying, electrostatic spinning, crosslinking or grafting) as well as composite mercury removal by new carbon materials (e.g. carbon nanotubes, graphene oxide) in latest research. The removel efficiency and influential factors of Hg²⁺ ions removel by chitosan and its derivatives are discussed in detail. Finally, we discuss the research prospects of chitosan adsorbent materials in treatment of mercury pollution.

Contents
1 Introduction
2 The mechanism of mercury removal by chitosan and its derivatives
2.1 The influencing factors of mercury removal by chitosan and its derivatives
2.2 The mechanism of selective mercury removal by chitosan and its derivatives
3 The study of chitosan and its derivatives removal of mercury
3.1 Physical modification of chitosan
3.2 Chemical modification of chitosan
3.3 Novel chitosan composite sorbents
3.4 The effect of mercury removal by different modification methods
4 Problems and prospects

Volatile organic compounds (VOCs) are poisonous organic compounds which pose a threat to environment and human health. Catalytic oxidation technology, which can convert VOCs into CO₂ and H₂O, is considered as one of promising techniques for VOCs removal. On the basis of the summary of VOCs removal technologies at home and abroad, catalytic oxidation method is emphatically introduced; besides, catalysts in common use, catalytic oxidation mechanism and existent problems are summarized in this paper. Finally, developmental trends of catalytic oxidation technology of VOCs are also presented. The results show that the core of noble catalysts is the optimization of effective supporters and the enhancement of resistance to catalyst poisoning. As for perovskite-type, spinel-type and other non-noble metal catalyst, it is the key to decrease the active temperature of catalysts. And it can be considered that the reduction ability, oxygen storage capacity and oxygen vacancy, which are critical factors determining catalyst performance for VOCs oxidation, can be improved by means of adjusting the compounding formula, morphological structure, particle size and specific surface area of catalysts and proceed to enhance catalyst performance. This review will offer certain value for reference to determine the proper catalyst for VOCs removal.

Contents
1 Introduction
2 Mechanism of catalytic oxidation
3 Catalysts of VOCs oxidation
3.1 Noble metal catalysts
3.2 Non-noble metal catalysts
4 Future trends
4.1 Noble metal catalysts
4.2 Non-noble metal catalysts
5 Conclusion

The purification of NO_x from diesel engine exhaust is an important topic in the field of air pollution control, which is significant for the improvement of current unban air quality. The selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) is one of the most promising technologies for the control of NO_x emission from diesel engine exhaust. In recent years, Cu-CHA catalysts, which are obtained from loading transition metal Cu on zeolites with chabazite (CHA) structure, have attracted much attention in the field of NH₃-SCR reaction, due to their excellent NH₃-SCR activity and hydrothermal stability. Cu-SSZ-13 and Cu-SAPO-34 are the two typical Cu-CHA catalysts. In this review, the progress of NO_x control in the field of diesel engine exhaust with Cu-CHA catalysts is stated from three aspects firstly, including the influences of preparation method, the effects of reaction condition and the NH₃-SCR reaction mechanism. Then, the application of M-CHA catalysts in NH₃-SCR reaction are elaborated, where M is limited as some other transition metal and rare earth metal. Meanwhile, the advantages of bimetallic-based CHA zeolites in NH₃-SCR reaction are identified. Based on these results, the possible improvement orientations for NH₃-SCR catalysts with CHA zeolites structure are also prospected.

Contents
1 Introduction
2 Application of Cu-CHA catalysts in NH₃-SCR
2.1 Cu-SSZ-13 used for NO_x purification
2.2 Cu-SAPO-34 used for NO_x purification
3 Application of Fe-CHA catalysts in NH₃-SCR
4 Application of bimetallic active center catalysts with CHA structure in NH₃-SCR
5 Conclusion and outlook

To investigate the formation of nitrogenous pollutants (NPs) during biomass thermo-chemical conversion (pyrolysis and gasification) is significant for the control of air pollution as these NPs are an important factor for the formation of PM_2.5. Research progress on the formation mechanism and influence factors of NPs during two processes are reviewed. Consistent conclusions from the literature can be summarized as follows:1) NPs formed from two processes resemble in their formation paths but differ in their types & components. Either NH₃ or HCN is confirmed to be main NPs for pyrolysis while NH₃ is dominant for gasification. 2) Comparing the influence factors, it is demonstrated that the increase of any factor such as the heating rate, the content of fuel nitrogen and the concentration of steam involved will enhance the formation of NPs for two processes. Meanwhile, the effect of temperature on the selectivity of NPs towards two processes are similar as well as higher temperature is inclined to decrease the amount of NPs. 3) Comparing the results of nitrogen distribution, it is found that the percentage of NPs in gaseous phase are approximately 50% for pyrolysis and as much as 90% for gasification. Therefore, to control the formation of NPs in gaseous phase is effective to reduce the pollutants during biomass thermo-chemical conversion. Meanwhile, based on the current conclusions obtained, the deficiencies of formation mechanism are summarized as well as the prospective developments are proposed for further research.

Contents
1 Introduction
2 Formation paths of NPs during biomass thermo-chemical conversion
2.1 Formation paths of NPs during pyrolysis process
2.2 Formation paths of NPs during gasification process
3 Effect of nitrogen occurrence characteristics in fuels
3.1 Effect of nitrogen structure
3.2 Effect of nitrogen content
4 Effect of thermal conditions
4.1 Effect of heating rate
4.2 Effect of temperature
5 Effect of reaction atmosphere
6 Effect of other conditions
6.1 Effect of the physicochemical properties of fuels
6.2 Effect of the catalytic performance of additives
7 Nitrogen distribution during two processes
8 Conclusion