Synchronous modification of ZIF-67 with cyclomatrix polyphosphazene coating for efficient flame retardancy and mechanical reinforcement of epoxy resin.

Cyclomatrix polyphosphazenes have attracted widespread attention in the field of polymer flame retardancy. Nevertheless, the optimal manifestation of their distinctive structural attributes and flame-retardant properties necessitates a judicious selection of condensation monomers and synergistic templates during the fabrication of polyphosphazene flame retardants. In our previous studies, it was discovered that when ZIF-67 is functionalized with polyphosphazene, the by-product HCl from phosphazene polycondensation causes etching on ZIF-67. Based on this "synchronous etching" effect, a series of hybrid materials comprising cyclomatrix polyphosphazene and ZIF-67, denoted as ZIF-67@PDS (PDS, poly-(cyclotriphosphazene-co-4,4'-diaminodiphenyl sulfone)), ZIF-67@PBS (PBS, poly-(cyclotriphosphazene-co-Bisphenol A)), and ZIF-67@PZS (PZS, poly-(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)), was synthesized utilizing DDS (4,4'-diaminodiphenyl sulfone), BPA (Bisphenol A), and BPS (4,4'-sulfonyldiphenol) monomers as precursors, respectively. Upon the incorporation of 2.0 wt.% of ZIF-67@PDS, ZIF-67@PBS, and ZIF-67@PZS, the flame retardant and mechanical characteristics of EP composites exhibited marked enhancement. The unique structural characteristics of hybrid and the synergistic effects of Co-P-N contribute to the improvement of comprehensive properties. Compared with pure EP, EP/ZIF-67@PZS has the best enhancement effect, and its pHRR, THR, and TSP decreased by 34.0%, 30.0%, and 40.5%, respectively. In terms of mechanical strength, ZIF-67@PZS also increases the flexural strength of EP by 37.42%. Relying on the "synchronous etching" effect, this study explores and verifies the effective combination of ZIF-67 and different types of polyphosphazenes, and obtains a series of ZIF-67-derived cyclomatrix polyphosphazene hybrids with different morphologies and properties in one step. It provides a new idea and strategy for the simultaneous modification of polyphosphazene materials and the preparation of multifunctional flame retardants in the future.

Transcriptome analysis indicates the mechanisms of BmNPV resistance in Bombyx mori midgut.

Bombyx mori nucleopolyhedrovirus (BmNPV) caused serious economic losses in sericulture. Analyzing the molecular mechanism of silkworms (B. mori) resistance to BmNPV is of great significance for the prevention and control of silkworm virus diseases and the biological control of agricultural lepidopteran pests. In order to clarify the defense mechanisms of silkworms against BmNPV, we constructed a near isogenic line BC8 with high resistance to BmNPV through the highly BmNPV-resistant strain NB and the highly BmNPV-susceptible strain 306. In this study, RNA-Seq technique was used to analyze the transcriptome level differences in the midgut of BC8 and 306 following BmNPV infection. A total of 1350 DEGs were identified. Clustering analysis showed that these genes could be divided into 8 clusters with different expression patterns. Functional annotations based on GO and KEGG analysis indicated that they were involved in various metabolism pathways. Finally, 32 BmNPV defense responsive genes were screened. They were involved in metabolism, reactive oxygen species (ROS), signal transduction and immune response, and insect hormones. The further verification shows that HSP70 should participate in resistance responses of anti-BmNPV. These findings have paved the way in further functional characterization of candidate genes and subsequently can be used in breeding of BmNPV resistance dominant silkworms.

Expressive Talking Avatars.

Stylized avatars are common virtual representations used in VR to support interaction and communication between remote collaborators. However, explicit expressions are notoriously difficult to create, mainly because most current methods rely on geometric markers and features modeled for human faces, not stylized avatar faces. To cope with the challenge of emotional and expressive generating talking avatars, we build the Emotional Talking Avatar Dataset which is a talking-face video corpus featuring 6 different stylized characters talking with 7 different emotions. Together with the dataset, we also release an emotional talking avatar generation method which enables the manipulation of emotion. We validated the effectiveness of our dataset and our method in generating audio based puppetry examples, including comparisons to state-of-the-art techniques and a user study. Finally, various applications of this method are discussed in the context of animating avatars in VR.

Enhancing char formation of flame retardant epoxy composites: Onigiri-like ZIF-67 modification with carboxymethyl ß-cyclodextrin crosslinking.

To enhance char formation of flame retardant epoxy (EP) composites, carboxymethyl ß-cyclodextrin (CM-ß-CD) is employed as an etchant for or ZIF-67 derivatives. In the early stage, etching plays a dominant role. The mismatch in size between CM-ß-CD opening and ZIF-67 pore leads to the stacking of carboxyl cobalt complexes on the shell. When the reaction time is prolonged, crosslinking occurs between carboxyl and hydroxyl groups. Crosslinked CM-ß-CD weakens and eventually stops the etching process. Triethyl phosphate (TEP), an additive to improve flame retardancy, is also absorbed on the shell in this one-pot synthesis. Herin, the synthesis of metal-organic framework (MOF) derivatives can impart multiple functions to MOF. This novel nanohybrid significantly improved flame retardancy of EP composites with only 2.0 wt% loading. The peak heat release rate (pHRR) and total smoke production (TSP) were reduced by 54.8 and 46.9%, respectively. The integrated multi-element system resulted in an expanded and reinforced char layer. This study proposes a simple and precise method for controlling the structure of MOF-carbohydrate hybrids through competition between chemical reactions.

Structure of Metal-Organic Frameworks Eco-Modulated by Acid-Base Balance toward Biobased Flame Retardant in Polyurea Composites.

Biobased-functionalized metal-organic frameworks (Bio-FUN-MOFs) stand out from the crowd of candidates in the flame-retardant field due to their multipathway flame-retardant mechanisms and green synthesis processes. However, exploring and designing Bio-FUN-MOFs tend to counteract the problem of compromising the flame-retardant advantages of MOFs themselves, which inevitably results in a waste of resources. Herein, a strategy in which MOFs are ecologically regulated through acid-base balance is presented for controllable preparation of Bio-FUN-MOFs by two birds with one stone, i.e., higher flame-retardant element loading and retention of more MOF structures. Specifically, the buffer layer is created on the periphery of ZIF-67 by weak etching of biobased alkali arginine to resist the excessive etching of ZIF-67 by phytic acid when loading phosphorus source and to preserve the integrity of internal crystals as much as possible. As a proof of concept, ZIF-67 was almost completely etched out by phytic acid in the absence of arginine. The arginine and phytic acid-functionalized ZIF-67 with yolk@shell structure (ZIF@Arg-Co-PA) obtained by this strategy, as a biobased flame retardant, reduces fire hazards for polyurea composites. At only 5 wt % loading, ZIF@Arg-Co-PA imparted polyurea composites with a limiting oxygen index of 23.2%, and the peaks of heat release rate, total heat release, and total smoke production were reduced by 43.8, 32.3, and 34.3%, respectively, compared to neat polyurea. Additionally, the prepared polyurea composites have acceptable mechanical properties. This work will shed light on the advanced structural design of polymer composites with excellent fire safety, especially environmentally friendly and efficient biobased MOF flame retardants.

A Gas-Steamed Route to Mesoporous Open Metal-Organic Framework Cages Enhancing Flame Retardancy and Smoke Suppression of Polyurea.

Up to now, metal-organic frameworks (MOFs) with open nanostructures have shown outstanding capabilities in trapping smoke particles compared to the original MOFs. However, only a few MOF-based strategies have been reported to synthesize hierarchical porous cages thus far, which are mainly restricted to environmentally unfriendly wet-chemical liquid methods. Herein, as a proof-of-concept, a gas-steamed metal-organic framework approach was designed to fabricate a series of cheeselike open cages with hierarchical porosity. Briefly, zeolitic imidazolate framework-67 (ZIF-67) and phytic acid were employed as precursor and etchant, respectively. Abandoning the conventional wet-chemical method, the coordination bond of ZIF-67 was cleaved by acidic steam, forming an open framework with a high specific surface area and a hierarchical porous structure. The universality of this method was also confirmed by the selection of different etchants. Impressively, they also show outstanding fume-toxic adsorption capability and labyrinth effects based on abundant and complex porous channels. At only 5 wt % loading, Co3O4@open ZIF-67 cage-2 (Co3O4@OZC-2) imparted polyurea (PUA) composites with a 21.2% limiting oxygen index, and the peak of heat release rate, total heat release, and total smoke production were reduced by around 37.5, 25.5, and 40.4%, respectively, compared to neat PUA. This work will shed light on the advanced structural design of polymer composites with high fire safety, especially smoke suppression performance, so as to obtain more feasible applications.

IFN-γ, SCF, MIP1b and IL-16 Were Associated with Risk of Diabetic Nephropathy: A Mendelian Randomization Study.

Background: The impact of inflammatory factors on the risk of diabetic nephropathy (DN) is inconsistent. Two-sample Mendelian randomization (MR) analyses were used to detect the causal role of inflammatory factors in DN risk. Methods: Inflammatory factor GWAS summary data were collected from a meta-analysis including 8,293 Finnish participants, and DN information was extracted from a GWAS of 213,746 individuals from FinnGen. The MR Pleiotropy Residual Sum and Outlier (MR-PRESSO) outlier test was used for the removal of horizontal pleiotropic outliers. Multivariable MR analysis was also used to adjust for pleiotropy. Results: IFN-γ [ORIVW: 1.33; 95% CI: 1.09-1.63; p=0.005] and SCF [ORIVW: 1.25, 1.02-1.52; p = 0.027] were associated with an increased risk of DN. MIP1b [ORIVW: 0.92; 95% CI: 0.85-0.98; p = 0.022] and IL-16 [ORIVW: 0.89, 0.81-0.99; p = 0.043] showed negative associations with the risk of DN. We validated our MR results with MR-PRESSO analyses. Significant horizontal pleiotropy was not found. Moreover, in the multivariable MR analysis, the associations between cytokines and DN risk remained. Conclusion: Our MR results based on genetic data contribute to a better understanding of the pathogenesis of DN and provide evidence for a causal effect of inflammatory factors on DN. These findings support targeting specific inflammatory factors to alleviate DN risk.

Hollow Superstructure In Situ Assembled by Single-Layer Janus Nanospheres toward Electromagnetic Shielding Flame-Retardant Polyurea Composites.

A dodecahedral superstructure consisting of a single layer of Janus spheres containing ZIF-67 nanodots is prepared by in situ polymerization, with ZIF-67 and bio-based phytic acid (PA) as templates and dopants. It is used to improve the flame retardant, electromagnetic (EMI) shielding, and thermal conductivity properties of polyurea (PUA). By adding 5 wt% polyaniline@cobalt phytate-2.0 (PANI@Co-PA-2.0), the peak of heat release rate and the peak of smoke production rate are reduced by 54.9 and 59.9%, respectively. The peak of CO and CO2 production also decreased by 46.2 and 53.1%, respectively. A decrease in the absorption intensity of aliphatic and aromatic volatiles is also observed. The fire safety of PUA is greatly improved. In addition, PUA/PANI@Co-PA-2.0 exhibits an EMI shielding capability of 22.4 dB with the help of reduced graphene oxide, which confirms the possibility of PUA material application in the field of electromagnetic shielding. The 5 wt% filler increases the tensile strength of the PUA matrix to 6.3 MPa, and the composite material obtains good thermal conductivity. This work provides a viable method for the preparation of a flame-retardant, conductive, and electromagnetic refractory PUA substrate.

Discovery, classification and application of the CPISPR-Cas13 system.

BACKGROUND: The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas system is an acquired immune system of bacteria and archaea. Continued research has resulted in the identification of other Cas13 proteins. OBJECTIVE: This review briefly describes the discovery, classification, and application of the CRISPR-Cas13 system, including recent technological advances in addition to factors affecting system performance. METHODS: Cas13-based molecular therapy of human, animal, and plant transcriptomes was discussed, including regulation of gene expression to combat pathogenic RNA viruses. In addition, the latest progress, potential shortcomings, and challenges of the CRISPR-Cas system for treatment of animal and plant diseases are reviewed. RESULTS: The CRISPR-Cas system VI is characterized by two RNA-guided higher eukaryotes and prokaryotes nucleotide-binding domains. CRISPR RNA can cleave specific RNA through the interaction between the stem-loop rich chain of uracil residues and the Cas13a protein. The CRISPR-Cas13 system has been applied for gene editing in animal and plant cells, in addition to biological detection via accurate targeting of single-stranded RNA. CONCLUSION: The CRISPR-Cas13 system offers a high-throughput and convenient technology for detection of viruses and potentially the development of anti-cancer drugs in the near future.

Rapid memory encoding in a recurrent network model with behavioral time scale synaptic plasticity.

Episodic memories are formed after a single exposure to novel stimuli. The plasticity mechanisms underlying such fast learning still remain largely unknown. Recently, it was shown that cells in area CA1 of the hippocampus of mice could form or shift their place fields after a single traversal of a virtual linear track. In-vivo intracellular recordings in CA1 cells revealed that previously silent inputs from CA3 could be switched on when they occurred within a few seconds of a dendritic plateau potential (PP) in the post-synaptic cell, a phenomenon dubbed Behavioral Time-scale Plasticity (BTSP). A recently developed computational framework for BTSP in which the dynamics of synaptic traces related to the pre-synaptic activity and post-synaptic PP are explicitly modelled, can account for experimental findings. Here we show that this model of plasticity can be further simplified to a 1D map which describes changes to the synaptic weights after a single trial. We use a temporally symmetric version of this map to study the storage of a large number of spatial memories in a recurrent network, such as CA3. Specifically, the simplicity of the map allows us to calculate the correlation of the synaptic weight matrix with any given past environment analytically. We show that the calculated memory trace can be used to predict the emergence and stability of bump attractors in a high dimensional neural network model endowed with BTSP.

The More, the Better? Social Capital Profiles and Adolescent Internalizing Symptoms: A Latent Profile Analysis.

Past research suggests that offline and online social capital are empirically linked to adolescent psychological adjustment. However, little is known regarding the implications of distinctive combinations of social capital for adolescent internalizing symptoms. The present study aimed to examine adolescent social capital patterns and their associations with internalizing symptoms by using latent profile analysis. A cross-sectional web-based survey was conducted among 1595 Chinese adolescents (mean age = 14.30 years, 50.7% male). All adolescents completed self-report questionnaires on their perceived offline and online social capital, depressive symptoms and anxiety symptoms. Latent profile analysis revealed four profiles of social capital: (1) Low Social Capital, (2) Moderate Social Capital, (3) High Social Capital, and (4) Only High Offline Social Capital. Further, analysis of covariance demonstrated that the Only High Offline Social Capital profile had significantly fewer internalizing symptoms than other three profiles. No statistical differences of internalizing symptoms were found between the other three profiles, except that the Moderate Social Capital profile showed fewer anxiety symptoms than the Low Social Capital profile. These findings suggest that more social capital does not equal to better mental health status. The social capital profiles and their associations with adolescent internalizing symptoms may provide practitioners with meaningful implications regarding the role of offline and online social capital in adolescent psychological adjustment.

Three-Dimensional Printing of Large Ceramic Products and Process Simulation.

Ceramic 3D printing is a promising technology that overcomes the limitations of traditional ceramic molding. It offers advantages such as refined models, reduced mold manufacturing costs, simplified processes, and automatic operation, which have attracted a growing number of researchers. However, current research tends to focus more on the molding process and print molding quality rather than exploring printing parameters in detail. In this study, we successfully prepared a large-size ceramic blank using screw extrusion stacking printing technology. Subsequent glazing and sintering processes were used to create complex ceramic handicrafts. Additionally, we used modeling and simulation technology to explore the fluid model printed by the printing nozzle at different flow rates. We adjusted two core parameters that affect the printing speed separately: three feed rates were set to be 0.001 m/s, 0.005 m/s, and 0.010 m/s, and three screw speeds were set to be 0.5 r/s, 1.5 r/s, and 2.5 r/s. Through a comparative analysis, we were able to simulate the printing exit speed, which ranged from 0.0751 m/s to 0.6828 m/s. It is evident that these two parameters have a significant impact on the printing exit speed. Our findings show that the extrusion velocity of clay is approximately 700 times faster than the inlet velocity at an inlet velocity of 0.001-0.010 m/s. Furthermore, the screw speed is influenced by the inlet velocity. Overall, our study sheds light on the importance of exploring printing parameters in ceramic 3D printing. By gaining a deeper understanding of the printing process, we can optimize printing parameters and further improve the quality of ceramic 3D printing.

Cross-sectional and longitudinal associations of adherence to the 24-hour movement guidelines with mental health problems among Chinese adolescents.

OBJECTIVE: This study aimed to examine the cross-sectional and longitudinal associations between meeting the 24-Hour Movement Guidelines (recommendations for the optimal amount of moderate-to-vigorous physical activity, screen time, and sleep duration per day) and mental health problems among Chinese adolescents. METHODS: A two-wave longitudinal survey was conducted in Huizhou, Guangdong province. A total of 906 junior high school students were recruited in the six-month follow-up survey. Moderate-to-vigorous physical activity, screen time, sleep duration, anxiety symptoms (GAD-7 score), and depressive symptoms (PHQ-9 score) were measured using a self-administered questionnaire. At baseline, participants were classified as meeting: 1) no recommendation, 2) one recommendation, 3) two recommendations, or 4) all three recommendations. RESULTS: Overall, the proportions of adolescents meeting moderate-to-vigorous physical activity, screen time, and sleep recommendations at T1 were 33.3%, 68.2%, and 64.7%, respectively. Cross-sectionally, the severity of anxiety and depressive symptoms at T1 significantly decreased as the number of recommendations met increased (adjusted regression coefficients [95% CI] for three recommendations met versus none: -2.80 [-4.05, -1.55] and - 3.42 [-4.85, -1.99], respectively). Longitudinally, adolescents who met three recommendations at T1 displayed lower anxiety and depressive symptoms six months later than those who did not (adjusted regression coefficients [95% CI]: -1.00 [-1.98, -0.02] and - 1.43 [-2.53, -0.32], respectively). Furthermore, meeting three recommendations was associated with the alleviation of depressive symptoms (adjusted OR [95% CI]: 0.39 [0.17, 0.90]). CONCLUSIONS: Promoting adolescents to adhere to the 24-Hour Movement Guidelines could be considered an intervention target for mental health problems at a population level.

Metal-organic framework-derived bird's nest-like capsules for phosphorous small molecules towards flame retardant polyurea composites.

The loading treatment of phosphorus flame retardants can mitigate their migration and plasticization effect. However, designing suitable carriers has remained a great challenge. Herein, two kinds of Co-based isomers, namely cobalt-cobalt layered double hydroxides (CoCo-LDH) and cobalt basic carbonate (CBC), were synthesized by employing ZIF-67 as a self-template, assemblied into two different nanostructures namely multi-yolk@shell CBC@CoCo-LDH (m-CBC@LDH) and solid CBC nanoparticles by facilely tuning the reaction time, which were employed as carriers, respectively. Subsequently, triphenyl phosphate (TPP)-loaded m-CBC@LDH (m-CBC-P@LDH) was prepared using TPP as the guest. The m-CBC@LDH with high specific surface area and hollow structure exhibited up to more than 30% of TPP loading. The peak of heat release rate and total heat release of polyurea composite blended with 5 wt% m-CBC-P@LDH reduced by 41.7% and 20.6% respectively, and the mechanical properties were less damaged. This work complements a feasible approach for preparation of metal-organic frameworks-derived flame retardant carriers.

Emotional Voice Puppetry.

The paper presents emotional voice puppetry, an audio-based facial animation approach to portray characters with vivid emotional changes. The lips motion and the surrounding facial areas are controlled by the contents of the audio, and the facial dynamics are established by category of the emotion and the intensity. Our approach is exclusive because it takes account of perceptual validity and geometry instead of pure geometric processes. Another highlight of our approach is the generalizability to multiple characters. The findings showed that training new secondary characters when the rig parameters are categorized as eye, eyebrows, nose, mouth, and signature wrinkles is significant in achieving better generalization results compared to joint training. User studies demonstrate the effectiveness of our approach both qualitatively and quantitatively. Our approach can be applicable in AR/VR and 3DUI, namely, virtual reality avatars/self-avatars, teleconferencing and in-game dialogue.

StyleVR: Stylizing Character Animations with Normalizing Flows.

The significance of artistry in creating animated virtual characters is widely acknowledged, and motion style is a crucial element in this process. There has been a long-standing interest in stylizing character animations with style transfer methods. However, this kind of models can only deal with short-term motions and yield deterministic outputs. To address this issue, we propose a generative model based on normalizing flows for stylizing long and aperiodic animations in the VR scene. Our approach breaks down this task into two sub-problems: motion style transfer and stylized motion generation, both formulated as the instances of conditional normalizing flows with multi-class latent space. Specifically, we encode high-frequency style features into the latent space for varied results and control the generation process with style-content labels for disentangled edits of style and content. We have developed a prototype, StyleVR, in Unity, which allows casual users to apply our method in VR. Through qualitative and quantitative comparisons, we demonstrate that our system outperforms other methods in terms of style transfer as well as stochastic stylized motion generation.

In-situ constructing self-supported NiO/RuO2 heterostructure for reinforced alkaline hydrogen evolution reaction.

Rationally designing a strongly coupled heterostructure with rich functional sites and high catalytic stability is essential for efficient energy conversion. This work synthesizes a self-supported NiO/RuO2 heterostructure for hydrogen production via facile dealloying following an in-situ electrochemical oxidation method. It only requires 88 ± 1 mV to drive a current density of -100 mA/cm2 in the alkaline electrolyte during hydrogen evolution reaction (HER), outperforming NiO, RuO2, and Pt foil. The higher anodic potential applied to the dealloyed ribbons results in lower overpotentials and faster reaction kinetics. Meanwhile, the catalytic activity and stability of the individual NiO can be significantly improved once coupled with a small amount of heterogeneous RuO2. The strong synergistic effect between NiO and RuO2 contributes to exposing abundant active sites, optimizing electronic structure, facilitating charge transfer at the interface, and most importantly, maintaining structural stability. These advantages make the self-supported NiO/RuO2 heterostructure a promising candidate for replacing the Pt-based catalysts.

Discovery of an Heparin-Binding Epidermal Growth Factor Domain Antibody from a Phage Library and Analysis of Its Inhibitory Effects in SKOV3 Cells.

Objective: Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), which binds to the EGF receptor, plays an important role in the occurrence and development of inflammation in various diseases. HB-EGF mediates the progression of ovarian cancer and is associated with disease prognosis. Thus, a specific humanized antibody to HB-EGF with high affinity is important. Methods: In this study, a humanized domain antibody (VH) against HB-EGF was discovered through phage display technology. The domain antibody was expressed in HB2151 cells and purified from the supernatant using protein L, and were used to test the its effect in invasion and migration of ovarian cancer SKOV3. Results: A domain antibody against HB-EGF was discovered, with a dissociation constant of ∼30 nM. Functional assays indicated that the domain antibody inhibited the functions of HB-EGF in promoting invasion and migration of SKOV3 cells. Conclusions: The selected domain antibody is a potential tool for developing novel drugs or therapies to combat ovarian cancer.

Prospect of thioredoxin as a possibly effective tool to combat OSAHS.

PURPOSE: Obstructive sleep apnea-hypopnea syndrome (OSAHS) is characterized by recurrent upper airway disturbances during sleep leading to episodes of hypopnea or apnea, followed by hypoxemia and subsequent reoxygenation. It is believed that this reoxygenation/reperfusion stage leads to oxidative stress, which then leads to inflammation and cardiovascular diseases. The treatments of patient with OSAHS include surgical and non-surgical therapies with various side effects and common complaints. Therefore, it is important to develop a new, safe, and effective therapeutic treatment. As a small-molecule multifunctional protein, thioredoxin (TRX) has antioxidant and redox regulatory functions at the active site Cys-Gly-Pro. TRX prevents inflammation by suppressing the production of pro-inflammatory cytokines rather than suppressing the immune response. METHODS: We review the papers on the pathophysiological process of OSAHS and the antioxidative and anti-inflammatory effects of TRX. RESULTS: TRX may play a role in OSAHS by scavenging ROS, blocking the production of inflammatory cytokines, inhibiting the migration and activation of neutrophils, and controlling the activation of ROS-dependent inflammatory signals by regulating the redox state of intracellular target particles. Furthermore, TRX regulates the synthesis, stability, and activity of hypoxia-inducible factor 1 (HIF-1). TRX also has an inhibitory effect on endoplasmic reticulum- and mitochondria-induced apoptosis by regulating the expression of BAX, BCL2, p53, and ASK1. CONCLUSION: Understanding the function of TRX may be useful for the treatment of OSAHS.

Multielement Flame-Retardant System Constructed with Metal POSS-Organic Frameworks for Epoxy Resin.

The direct coordination between polyhedral oligomeric silsesquioxane (POSS) and Co forms an assembly of nanoparticles with low specific surface area and leads to a poor dispersion state in the epoxy resin matrix, resulting in unsatisfactory flame-retardant efficiency. Metal-organic frameworks (MOFs), for instance, ZIF-67, provide not only the cobalt element but also the porous framework that endows the nanocomposite of MOFs and POSS with high specific surface area and abundant Co sites in the silica skeleton. Herein, ZIF-67 is hybridized with octacarboxyl POSS, resulting in the removal of the alkaline ligand to form novel metal POSS-organic frameworks (MPOFs). The size differences for organic groups and silica nanocages of POSS vs. micropores of ZIF-67 gave rise to a reverse click reaction, reforming octavinyl POSS isolated on the outer surface of the Co complex, which could be further modified by a phosphorous flame retardant using an addition reaction. The obtained MPOFs-P with 2 wt % loading in epoxy resin could improve the limiting oxygen index value of the composites to 27.0% and pass the V-0 rating in the UL-94 test. Meanwhile, the peaks of the heat release rate and especially the total smoke production were reduced by 46.6 and 25.2%, respectively. The robust char layer reduces the emission of toxic gas CO by 39.8%. The above epoxy product with promising flame retardancy also improved mechanical properties, thanks to the filler with a unique nanostructure. The ingenious work offers enlightenment for the hybridization method of MOFs and POSS to fabricate a multielement flame-retardant system for epoxy resin with high efficacy.