Phosphorus containing flame retardants with lower oxidation states (such as +1 or +3 valence) are often used to improve fire safety of polymers due to their excellent gas-phase flame retardancy. Unfortunately, these quenching radical-chain reactions also lead to incomplete combustion and, consequently, dense smoke. Transition metal ions can offset this drawback by catalyzing char formation, thereby reducing both heat and smoke release. Whether monovalent-phosphorus ligands combined with different metal centers can deliver balanced flame retardancy in flexible polyurethane foam (FPUF) has, however, remained an open question.In this work, three coordination compounds of diphenylphosphinic acid (DPPA) with Cu2+, Co2+, and Fe3+ (DPPA-Cu, DPPA-Co and DPPA-Fe) were compared. At 5 wt% (with respect to polyol 330), DPPA-Cu raised the limiting oxygen index (LOI) of FPUF to 21.3%, confirming pronounced gas-phase flame retardancy. The same loading of DPPA-Co or DPPA-Fe almost completely inhibited the gas-phase interaction of DPPA. The foam containing DPPA-Fe (5DPPA-Fe foam) did not produce molten droplets during vertical combustion. We analyzed the flame-retardant mechanism of different samples and the resulting droplets and residual char after combustion, revealing the decomposition mechanism of FPUF by different metal ions. This study provides ideas for the design of FPUF flame retardants.

Flammability is currently one of the main safety constraints that limit the further application extension of polymeric materials. The development of effective fire-retardant solutions that are both environment-friendly and have little impact on matrix properties is of great importance for polymer safety. By blending metal-organic frameworks (MOFs) into inorganic flame retardants, the prepared composites can take advantages of both MOFs and inorganic flame retardants, i.e. tunability of structure and high specific surface area for the former and thermal stability for the latter. Therefore, blending MOFs into inorganic flame retardants is a robust approach to prepare synergistic fire-retardant solutions. Due to the complexity of combustion reactions, different kinds of flame retardants may exhibit different flame retardant mechanisms. Classifying flame retardent systems based on their mechanisms will be helpful to reveal the intrinsic relationship among structure, property, and fundamental idea. Following the above concept, preparing flame retardent system by blending different kinds of MOFs and inorganic particles will be more effective in both design strategy and flame retardant performance. In this review, different MOF-inorganic material flame retardant systems will be summarized according to their flame retardant behaviors, and current challenges and future developments in this field will also be discussed for a prospective look at the systematic design of materials.

Flexible polyurethane foam (FPUF) is widely used in daily applications and thermal insulation materials owing to its excellent stability and comfort. However, its high flammability and the substantial production of molten droplets during combustion limit its use. Layer-by-layer self-assembly (LBL) has emerged as an efficient strategy for imparting flame retardancy to FPUF, particularly through coatings based on metal ions-polyphenol coordination networks; it can efficiently suppress heat and smoke release during combustion. Here, we have developed an alternating layer composed of polyethyleneimine (PEI)/tannic acid (TA) + Fe(NO3)3/polyacrylic acid (PAA) + montmorillonite (MMT). This coating not only markedly reduces the peak heat release rate (PHRR) at low add-on levels but also efficiently suppresses smoke emission from FPUF. Cone calorimetry results show that five layers foam a modest weight gain of only 6.6 wt% achieves reductions of 43% in PHRR, 59% in peak smoke production rate (PSPR), and 48% in total smoke production (TSP) compared to pristine FPUF. Moreover, the coating exhibits excellent water resistance: after 15 days of water immersion, the PHRR and TSP of the coated foam remain reduced by 35% and 27%, respectively, relative to uncoated FPUF. Further analysis of the flame-retardant mechanism, offering valuable insights for the rational design of high-performance flame-retardant coatings for FPUF.

Polymers are valued in numerous critical applications due to their lightweight nature, ease of processing and affordability. A major drawback is their natural flammability, which poses a serious risk, as combustion is often accompanied by intense heat release, molten drips and toxic smoke, all of which can easily lead to fire hazards. Traditional flame retardants, such as phosphorus-based compounds, clays and carbon-based materials, often suffer from drawbacks including poor dispersion, weak compatibility with polymer matrices and low char-forming efficiency. ZIF-67, as an important member of metal-organic framework (MOF) materials, has become a promising alternative owing to its exceptional specific surface area, regular pore configuration and cobalt-based catalytic sites. These characteristics enable ZIF-67 to form multi-scale composite systems with various flame retardants, thereby overcoming the individual limitations of each. Building on these unique properties, significant research efforts have focused on integrating ZIF-67 with various flame retardants to create high-performance hybrid systems. This review article provides a detailed overview of strategies for combining ZIF-67 with diverse categories of fire retardants and analyzes the resulting enhancements in fire resistance across various polymer matrices. In addition, this review addresses the prospects and ongoing challenges regarding the advancement of ZIF-67-based flame retardant systems.

Metal-organic frameworks (MOFs) are a class of materials with highly ordered porous structures. They are frequently utilized as flame retardants (FRs) to enhance the flame retardancy of polymers due to their distinctive high specific surface area, excellent porosity, and thermal stability. However, MOFs are often employed as synergists in combination with other flame retardants that possess superior flame retardant properties, owing to their limited effectiveness when used in isolation. Phosphorus flame retardants and halogen flame retardants are common primary flame retardants with recognized efficient flame retardant properties. A significant advantage of phosphorus flame retardants is that they emit fewer toxic gases during combustion, and they are widely used as a key component in modern polymer flame retardants due to their properties. A prominent trend in recent years has been the use of phosphorus flame retardants as the primary flame retardant in combination with the use of MOFs as synergists for polymer flame retardancy. This combination is more effective in improving the flame retardancy of polymers during combustion by, for example, catalyzing the formation of a denser carbon layer, while at the same time enhancing the dispersion of the filler in the polymer, thereby reducing the impact of phosphorus-containing FRs on mechanical properties. The utilization of such flame retardants is an emerging trend, as evidenced by numerous studies that have demonstrated their effectiveness. This paper examines the application of various MOFs-P FRs in different polymer systems, analyzing their impact on flame retardancy and mechanisms. It also compares MOFs-P FRs with other commercial phosphorus-based FRs, discusses the current state of it, and explores future applications and challenges.

Polylactic acid (PLA) is a promising renewable polymer material known for its excellent biodegradability and good mechanical properties. However, its easy flammability and slow natural degradation limit its further applications. In this work, we designed a multi-layer core-shell flame retardant (ZIF-8@CH@APP) with interfacial characteristics through organic-inorganic hybrid technology. The interfacial functionalization of inorganic flame retardant ammonium polyphosphate (APP) was carried out with bio-based chitosan (CH), and the three-dimensional network was constructed by in-situ growth of metal-organic framework (ZIF-8). With 7 wt% addition of ZIF-8@CH@APP, the PLA composite exhibited excellent flame retarded properties. It showed V-0 vertical burning (UL-94) grade, and reduced total smoke produce (TSP) (0.2 m2). Additionally, the PLA/7 % ZIF-8@CH@APP composite exhibited higher degradation rate at mild condition. Additionally, the final degradation product of ZIF-8@CH@APP was confirmed to be DL-lactic acid. The design not only improves the interface compatibility between inorganic phase and polymer matrix, but also realizes the double breakthrough of flame retardant and catalytic degradation function through physical-chemical synergism, providing an innovative solution for the recycle of PLA material.

Water evaporation-based power production and interfacial solar steam generation are considered as the biggest promising techniques for resolving global freshwater and energy issues. Nevertheless, it remains challenging to construct solar evaporators for superior electrical energy generation and high evaporation flux at the same time; besides, the impact of the surface charge on the effectiveness of water evaporation power generation is unclear. Herein, we report the preparation of zinc-based metal-organic frameworks (ZIF-8) by ball milling and the controllable carbonization of ZIF-8 to prepare N-doped porous carbon polyhedron (NDPCP). Subsequently, a solar evaporator and energy harvesting device based on NDPCP is prepared to produce freshwater and generate electricity. The NDPCP evaporator has good hydrophilicity, high sunlight, strong photothermal conversion capability, and low enthalpy of vaporization. The conversion efficiency is 90.9 % and the evaporation rate is 2.86 kg m- 2 h- 1. By using the NDPCP-700 evaporator-based power generating unit, an indoor open circuit voltage of 202 mV is generated. In the outdoor, the NDPCP-700 evaporator realizes the freshwater production of 3.01 kg m- 2 and open circuit voltage of 351 mV. We demonstrate that power production requires high specific surface area, many functional groups, and well-developed pore channels. Positively charged ions are inhibited in positively charged nanochannels, according to molecular dynamics (MD) results, which causes a possible distinction between the top and bottom ends. This study not only reveals the feasibility of interfacial solar evaporators constructed from materials with positive surface charges, but also provides opportunities for developing advanced freshwater electricity co-generation devices.

Phosphorus containing flame-retardants with low oxidation states are widely used in Flexible polyurethane foam (FPUF) due to their excellent gas-phase flame retardancy. However, achieving good migration resistance in prepared flame retardant while balancing or even improving the mechanical properties (such as ductility, good rebound ability) and flame retardancy of FPUF remains a challenging issue. To solve the above problem, we have designed diphenylphosphine oxide silicon glycol (DPPSG) that combines a phosphorus-based flame retardant group with a Si-O-C bond structure. Chemically linking DPPSG into the molecular chain of flexible polyurethane foam and mechanical properties at the same time. On one hand, DPPSG has good compatibility with polyether polyols 330, reacting uniformly with isocyanates and participating in the foaming and gelation process of FPUF. This ensures its enduring flame retardancy. On the other hand, the tensile strength and elongation at break of the flame retardant foam (10DPPSG foam) prepared by adding 10% DPPSG of polyether polyol 330 increased by 71.4% and 77.6% respectively. Moreover, even after 100 cycles of compression rebound testing, 10DPPSG foam exhibited excellent elasticity with a permanent compression deformation rate of only 4.9%. This work provides a new approach to develop FPUF that achieves a balance between mechanical and flame-retardant properties.

Epoxy resin (EP) has been widely used in many fields due to its excellent physical and chemical properties. However, its inherent flammability limits its application in some fields, and the development of efficient and environmentally friendly new flame retardants has become a research hotspot. In recent years, researchers have been committed to developing new flame retardants to improve the flame retardant properties of EP. The development of synergistic flame retardant systems, combined with the advantages of various flame retardants, has become a research trend. In this paper, the application progress of three kinds of new flame retardants in EP, including nano-materials, organic materials, and inorganic materials, is summarized. Their synthesis methods, structural design, and application prospects are compared, and a summary and prospect are given.

Metal-organic frameworks (MOFs), assembled from inorganic metal centers (metal ions or clusters) and organic ligands, possess distinctive features such as structural designability, high surface area, and tunable functionalities. In the past decade, MOFs have displayed substantial merits when utilized as innovative flame retardants in the realm of polymeric materials. A current focus is on the flame-retardant effects of MOFs in thermosetting plastics, yielding substantial achievements; however, systematic investigations into thermoplastic polymers, which are more widely used, remain limited. The flame-retardant mode of action for miscellaneous types of MOFs and their applications in polymeric matrices, with particular emphasis on recent advances in thermoplastic systems, are summarized. Furthermore, existing challenges and future perspectives are identified.

In recent years, metal-organic frameworks (MOFs) are often used as fillers to enhance the flame retardancy of polymers due to their unique physical and chemical properties, and their unique high surface area and regular pore structure allow them to be used in various types of polymers as new flame retardants by combining with other types of modifiers using modification and hybridisation or by forming derivatives on their own. Clay as a common natural modifier has been used for a long time to modify the flame retardant properties of polymers. Still, due to its poor dispersibility, it is usually necessary to combine with other synergists to improve the dispersibility in polymers. MOFs are often used as synergists to enhance clay dispersibility in polymers, thereby improving their flame retardant properties. This subject has been the focus of increasing academic scrutiny in recent years, resulting in rapid advancements. Consequently, it is imperative to provide a comprehensive review of this development for novices in the field. This paper, after introducing the synthesis methods of different MOFs/clay flame retardants, reviews the application of MOFs and clay flame retardants in polymer materials, categorized by type. It examines their synthesis methods, impacts on flame resistance and mechanical performance, and other fields of application. The study concludes with prospects for developing these materials as multifunctional retardants, addressing future challenges and opportunities.

Epoxy resins (EP) is classic thermosetting material, but its flammability severely limits its usage. In this paper, a novel flame retardant (FePor@PZS) was synthesized by growing polyphosphazene (PZS) in situ onto the surface of iron porphyrin organic frameworks (FePor). Attributed to the synergistic flame retardant system of nitrogen, phosphorus and iron elements, FePor@PZS endowed excellent fire safety property to EP. Upon incorporating 2 wt% FePor@PZS, EP/FePor@PZS got an LOI value of 27.3%, achieving the V-1 level in the test of UL-94. Besides, the peak rate of heat release, release of total heat, peak rate of smoke production, production of total smoke, peak rate of CO2 production and peak rate of CO production of EP/FePor@PZS were decreased by 31.8%, 21.5%, 17.5%, 22.3%, 34.8% and 73.5%, respectively, and the quantity of residual carbon increased from 9.69% to 27.86%, compared with neat EP. FePor could break off to form a single pyrrole ring to promote the generation of the early carbon layers. Additionally, the Fe element in FePor and the P element in PZS played a role of catalytic carbonization. Meanwhile, PZS could decompose into non-combustible gases, and produce PO and HPO radicals to terminate the EP chain-opening reaction. This research gives a novel approach for the application of porphyrin derivatives in flame retardant composites. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Ferrocene (Fc) and metal-organic frameworks (MOFs) are established as effective functional additives in polymer composites, known for their synergistic effects. However, simple physical mixing does not fully harness their potential. To optimize their performance, we developed a method to graft ferrocene onto zeolitic imidazolate frameworks (ZIFs) via a Schiff base structure, followed by constructing a ferrocene-based covalent metal-organic porous polymer (CMOPP) network using Friedel-Crafts alkylation. This approach addresses the mesoporous structure limitation in ZIFs. During this process, the imidazole ligands are etched, yielding a yolk-shell structured, hierarchically nanoporous flame retardant. The synergy between ferrocene and ZIF significantly enhances the UV protection of epoxy resin, with a 99.1% reduction in UV transmittance. Additionally, ferrocene improves the filler-matrix compatibility, increasing tensile strength by 15.1%. This combination of flame-retardant elements and the porous structure's adsorption capacity imparts exceptional flame retardancy and smoke suppression to the epoxy resin, evidenced by a Limiting Oxygen Index of 28.3% and a V-0 rating in the UL-94 test. Notable reductions include 56.5% in peak heat release rate, 55.1% in peak smoke production rate, and 71.6% in peak carbon monoxide production. This work introduces a novel strategy for designing high-performance multifunctional flame retardants.

The utilization of Polyurethane foaming materials (PUF) to seal coal fissures presents a significant challenge due to the substantial heat generated during the reaction process, potentially accelerating fires. In order to study this issue, we propose a novel low-heat polymerization mechanism by incorporating a hydrated salt phase change composite that efficiently absorbs polymerization heat while encapsulating liquid water using expanded graphite (EG). Our findings demonstrate that integrating 10 % EG-6 leak-free phase change material effectively reduces the reaction temperature to a safer 91.4 degrees C, ensuring minimal impact on the inherent properties of the material. Thorough analyses via TGA and in-situ IR experiments reveal a noteworthy 17 degrees C elevation in the modified PUF's thermodynamic characteristic temperature point. Additionally, we developed a mixed combustion model of PUF and coal to investigate the gas generation pattern of polyurethane in the mine-filled state where fire occurs. Specifically, the introduction of PUF reduced O2 consumption and CO production while increasing CO2 and C2H4 production, which is consistent with the reality of increased carbon hydrocarbon gases being monitored downhole. These findings suggest a synergistic, mutually beneficial relationship between the two during the lowtemperature oxidation stage. This research offers perspectives for the development of polymer materials for coal mines and the safe application of actual filling.

It is of great scientific and economic value to recycle waste poly(ethylene terephthalate)(PET)into high-value PET-based metal organic frameworks(MOFs)and further convert it into porous carbon for green energy storage applications.In the present study,a facile and cost-effective hydrothermal process was developed to direct recycle waste PET bottles into MIL-53(Al)with a 100%conversation,then the MOF-derived porous carbon was assembled into electrodes for high-performance supercapacitors.The results indicated that the as-synthesized carbon exhibited high SSA of 1712 m2 g-1 and unique accordion-like structure with hierarchical porosity.Benefit to these advantageous characters,the assembled three-electrode supercapacitor displayed high specific capacitances of 391 F g-1 at the current density of 0.5 A g-1 and good rate capability of 73.6%capacitance retention at 20 A g-1 in 6 mol L-1 KOH electrolyte.Furthermore,the assembled zinc ion capacitor still revealed outstanding capacitance of 335 F g-1 at 0.1 A g-1,excellent cycling stability of 92.2%capacitance retention after 10 000 cycles and ultra-high energy density of 150.3 Wh kg-1 at power density of 90 W kg-1 in 3 mol L-1 ZnSO4 electrolyte.It is believed that the current work provides a facile and effective strategy to recycle PET waste into high-valuable MOF,and further expands the applications of MOF-derived carbons for high-performance energy storage devices,so it is conducive to both pollution alleviation and sustainable economic development.

Polyurethane (PU) filling materials are typically utilized in coal mines for filling and fortification in order to guarantee safe support structures. Existing PU filling materials are prone to polymer fires, and the current method of using additives to cool them down has the problem of the additive absorbing heat in advance to weaken the PU foam wall and reduce the mechanical properties. This article addresses the problem of the mismatch between the phase change heat absorption of hydrated salts and the exothermic polymerization of PU. This article discusses the thermal delay matching of phase change materials based on the exhalation completion time of polyurethane. It then presents a method for preparing thermally delayed phase-change hydrated salt materials using thermal insulation and porous composites, which allows for the low thermal polymerization of hydrated salt phase-change composite polyurethane. Low-heat exothermic polyurethane materials offer several advantages over their original polyurethane counterparts, including a lower exothermic heat output (with a 30 degrees C drop in maximum central temperature), 3-4 times higher foaming volume, and a 40% decrease in smoke density grade. This paper reveals the adaptive matching mechanism between the polyurethane curing exotherm and hydrated salt phase change heat absorption. The findings have significant implications for promoting the development of mining polymer material technology.

Nanoscale Zr-based metal-organic framework (MIP-202) particles were successfully prepared via a seeds-assisted hydrothermal secondary synthesis. The uniformly-shaped MIP-202 particles exhibit excellent performance on selective CO 2 adsorption from CO 2 /CH 4 and CO 2 /N 2 mixtures. At 298 K and 1 bar, the uptake ratios of CO 2 /CH 4 and CO 2 /N 2 of MIP-202 particles are as high as 32.6 and 65.2, respectively. The IAST (ideal adsorbed solution theory)-predicted selectivities of CO 2 /N 2 (50/50, v/v) and CO 2 /CH 4 (50/50, v/v) reach to 4.5 × 10 10 and 102.2, respectively. The breakthrough experiments further demonstrate that the CO 2 /CH 4 and CO 2 /N 2 mixtures can be efficiently separated through an adsorption column packed with MIP-202 particles. In addition, the as-prepared MIP-202 particles had a low iso-enthalpy of adsorption of CO 2 of 32.95 kJ/mol, which is favorable for the regeneration of the adsorbent. Herein the as-prepared MIP-202 is a potential material for efficient separation of CO 2 from CH 4 or N 2 through an energy- and cost-saving CO 2 capture process.

Highly active and stable oxygen evolution reaction (OER) electrocatalysts for water electrolysis are currently in high demand. Herein, a rationally designed three-dimensional (3D) CoFe selenide porous array (Fe-CoSe PA) is synthesized through ion exchange from zeolitic imidazolate framework-L (ZIF-L) nanoarray, followed by a facile selenization under hydrothermal conditions for OER electrocatalysis. During the OER process, the surface of Fe-CoSe PA is rapidly oxidized to CoFe oxides/hydroxides, which prevents the inner layer from being oxidized. Benefiting from the high porosity, abundant active sites, and the high conductivity of inner Fe-CoSe, Fe-CoSe PA exhibits excellent OER performance, with an overpotential of 285 mV at a current density of 10 mA cm-2, and a small Tafel slope of 68 mV dec-1, as well as high stability under 50 h of continuous testing. The present work could provide a facile route for fabricating 3D porous selenides for highly efficient OER catalysis.

The development of highly efficient non‐precious metal electrocatalysts for the oxygen evolution reaction (OER) in low‐grade or saline water is currently of great importance for the large‐scale production of hydrogen. In this study, by using an electrochemical activation pretreatment, metal oxy(hydroxide) nanosheet structures derived from self‐supported nickel–iron phosphide and nitride nanoarrays grown on Ni foam are successfully fabricated for OER catalysis in saline water. It is demonstrated that the different NiOOH and NiOOH@FeOOH (NiOOH grown on FeOOH) structures are generated from nickel–iron nitride and phosphide, respectively, after electrochemical activation. In particular, the NiOOH@FeOOH heteroarchitecture shows outstanding electrocatalytic performance with an ultralow overpotential of 292 mV to drive the current density of 500 mA cm −2 . An unconventional dual‐sites mechanism (UDSM) is proposed to address the OER process on NiOOH@FeOOH and show that the FeOOH underlayer plays a critical role regarding the enhanced OER activity of NiOOH. The new possible UDSM involving two reaction sites presents a different understanding of the OER process on multi‐OH layer complexes, which is expected to guide the design of heteroarchitecture electrocatalysts.