Phosphonate Groups Research Articles

Mesoscale Morphologies of Nafion-Based Blend Membranes by Dissipative Particle Dynamics

Polymer electrolyte membrane (PEM) composed of polymer or polymer blend is a vital element in PEM fuel cell that allows proton transport and serves as a barrier between fuel and oxygen. Understanding the microscopic phase behavior in polymer blends is very crucial to design alternative cost-effective proton-conducting materials. In this study, the mesoscale morphologies of Nafion/poly(1-vinyl-1,2,4-triazole) (Nafion-PVTri) and Nafion/poly(vinyl phosphonic acid) (Nafion-PVPA) blend membranes were studied by dissipative particle dynamics (DPD) simulation technique. Simulation results indicate that both blend membranes can form a phase-separated microstructure due to the different hydrophobic and hydrophilic character of different polymer chains and different segments in the same polymer chain. There is a strong, attractive interaction between the phosphonic acid and sulfonic acid groups and a very strong repulsive interaction between the fluorinated and phosphonic acid groups in the Nafion-PVPA blend membrane. By increasing the PVPA content in the blend membrane, the PVPA clusters’ size gradually increases and forms a continuous phase. On the other hand, repulsive interaction between fluorinated and triazole units in the Nafion-PVTri blend is not very strong compared to the Nafion-PVPA blend, which results in different phase behavior in Nafion-PVTri blend membrane. This relatively lower repulsive interaction causes Nafion-PVTri blend membrane to have non-continuous phases regardless of the composition.

High Proton Conduction Behavior of a Water-Stable Cadmium Organic Framework and Its Polymer Composite Membranes

A water-stable metal-organic framework material of [Cd2 (pbdc)(H2O)3](1) has been synthesized based on H4pbdc (H4pbdc = 5-phosphonobenzene-1,3-dicarboxylic acid) ligands and Cd2+ ions. The Cd2+ ions are interacted with phosphonate and carboxylate groups to form infinitely extending one-dimensional chains, which are then bridged by pbdc ligands to generate a three-dimensional structure. AC impedance study found that the proton conductivity of compound 1 is 2.32 × 10−4 S·cm−1 at 333 K and 98% RH. Many MOF-polymer composite materials have excellent properties (such as heat resistance, high proton conductivity, etc.) and can be used in fuel cells and other fields. Thus, compound 1 was added to the CS matrix to prepare a series of composite membrane 1@CS-X (X = 1%, 3%, 5%, and 7% wt), which have good thermal stability and high proton conductivity. Under the same conditions, the effects of the 1@CS-X composite membranes on proton conduction are better than that of 1, which is caused by the hydrogen bond network constructed between CS and 1, and that provides a continuous channel for proton transfer. Strikingly, the proton conduction value of 1@CS-3 reached 1.10 × 10−2 S·cm −1 353 K and 98% RH, which is much better than many recently reported MOF-polymer composites.

(Invited) Surface Modification of Dye-Sensitized Hydrogen-Evolving Photocatalyst for Z-Scheme Solar Water Splitting

Z-scheme water splitting system composed of water reduction and oxidation photocatalysts coupled with redox-reversible electron mediator has attracted considerable attention because of the promising activity for water splitting under visible light irradiation. To improve the activity of Z-scheme water-splitting photocatalyst, how to achieve the one-way electron transfer from O2 evolution photocatalyst to H2 evolution photocatalyst through electron mediator is crucial. Dye-sensitization is one of the promising approaches not only to enhance the light absorption ability but also to improve the charge separation efficiency at the dye-semiconductor interface. We recently found that the multilayering of Ru(II) dyes on the surface of water reduction catalyst Pt-TiO2 nanoparticle (nRu@Pt-TiO2, n = number of layers of Ru(II) dyes) significantly improved the photocatalytic H2 evolution activity.[1] In this work, to enhance the electron donation from iodide, we have synthesized two different 2Ru@Pt-TiO2 nanoparticles with different surface structures: P-2Ru@Pt-TiO2 having phosphate groups on the surface and ZrP-2 Ru@Pt-TiO2 with Zr4+-phosphate groups on the surface as well as our previously reported 2Ru@Pt-TiO2 without any surface phosphonates.[2] Figure shows the results of photocatalytic H2 evolution reactions in 0.5 M aqueous KI solutions of three kinds of dye-double-layered nanoparticle photocatalysts with different surface structures. The amount of H2 produced after 6 h of light irradiation increased in the following order: 2Ru@Pt-TiO2 < P-2Ru@Pt-TiO2 < ZrP-2Ru@Pt-TiO2 . Notably, the AQY of ZrP-2Ru@Pt-TiO2 in the first hour of reaction was approximately 1%. The Ru(III)/Ru(II) redox potential of Ru(II)dye with phosphonic acid groups was reported to be shifted positively to less than 0.1 V by immobilization to the TiO2 surface or by coordination bond formation with Zr4+ cations[3], suggesting that the binding of Zr4+ to the phosphonic acid groups of Ru(II) dye has little effect on the driving force of the electron donation reaction from the iodide. The zeta potential of ZrP-2Ru@Pt-TiO2 was estimated to be +7 mV without KI, and it negatively shifted to −6 mV in the presence of 0.5 M KI. On the other hand, the shift of P-2Ru@Pt-TiO2 was estimated to be smaller (from −7 to −12 mV). The negative shifts in the 0.5 M KI aqueous solution could be ascribed to the attraction of iodide anions to the nanoparticle surface by electrostatic interactions with the surface Zr4+ cations in the case of ZrP-2Ru@Pt-TiO2, and by hydrogen-bonding interactions with the surface phosphonic acids for P-2Ru@Pt-TiO2. These results suggest that the surface structure of Ru(II) dye-sensitized Pt-TiO2 nanoparticle photocatalyst has a great influence on the reactivity with the redox mediator. Details will be discussed. Figure 1

Metal adsorption properties of multi‐functional PAMAM dendrimer based gels

AbstractMetal adsorption studies are getting important and there are many functional adsorbents developed recently. Here, we report the synthesis of multifunctional PAMAM G2 (polyamidoamine) possessing methacryl, amine, hydroxyl and phosphonate groups used in free radical curing gel formulations. UV curable gel is conducted in the presence of acrylamide, bisacrylamide, and polyethylene glycol diacrylate. Adsorption study of the resulting novel sorbents (gels) are carried out with a series of metals. Through a comprehensive study, structure–property relationship of the series gels is conducted by using different amount of amine, hydroxyl, and/or phosphonate ester groups on the PAMAM G2. Selected metals are Cr3+, Fe3+, Ni2+, Cu2+, Ag+, and Cd2+ within a series of hard, intermediate, and soft ionic species. Adsorption study is carried out in pure water environment at neutral pH. Metal ions removal percentages and adsorption capacities of gel adsorbents are calculated by using atomic absorption spectroscopy. There is relationship between the overall functional groups presence in gel formulation and swelling densities for removing the metal ions. Introducing dendrimer into the gel formulation enhanced the metal ions adsorption against to Bare GEL formulation which do not possess dendrimer units. Consequently, the maximum removal efficiency has been obtained for Cr3+ and Fe3+.

Palladium-Catalyzed Cascade to Benzoxepins by Using Vinyl-Substituted Donor-Acceptor Cyclopropanes.

A palladium‐catalyzed intermolecular cascade (4+3) cyclocondensation of salicylaldehydes and vinylcyclopropanes is reported. A key feature of the reaction is the use of a phosphonate group as an acceptor moiety on the cyclopropane, exploiting its propensity to undergo olefination with aldehydes. Subsequent O‐allylation enabled the formation of a range of substituted benzoxepinsWith a novel chiral ligand, the products were obtained in generally good yield and with reasonable enantioselectivity.

Palladium‐Catalyzed Cascade to Benzoxepins by Using Vinyl‐Substituted Donor–Acceptor Cyclopropanes

AbstractA palladium‐catalyzed intermolecular cascade (4+3) cyclocondensation of salicylaldehydes and vinylcyclopropanes is reported. A key feature of the reaction is the use of a phosphonate group as an acceptor moiety on the cyclopropane, exploiting its propensity to undergo olefination with aldehydes. Subsequent O‐allylation enabled the formation of a range of substituted benzoxepinsWith a novel chiral ligand, the products were obtained in generally good yield and with reasonable enantioselectivity.

Recovery of rare earth elements (Lu, Y) by adsorption using functionalized SBA-15 and MIL-101 (Cr)

Due to increasing application in the green energy sector, rare earth elements (REEs) have become a precious commodity in the international market. The REEs, Yttrium (Y) and Lutetium (Lu) are used as catalysts in wide array of industries. SBA-15 modified with 1,4-phthaloyl diamido-propyltriethoxysilane (1,4-PA-APTES) ligands; and chromium based metal organic frameworks (MOF) modified with PMIDA (MIL-101-PMIDA) were prepared in this study as potential adsorbents for recovery of these elements. The adsorption capacities for Lu and Y on virgin SBA-15 were negligible. After modification of SBA-15, the Langmuir adsorption capacities for Lu and Y significantly increased to 17.0 and 17.9 mg/L, respectively. The Langmuir adsorption capacities of Lu and Y on PMIDA modified MIL-101 (MIL-101-PMIDA) were 63.4 and 25.3 mg/g, respectively. Higher adsorption capacities of the MOF are due to its higher surface area (1050 m2/g) and beneficial functional groups such as phosphonic group present on the adsorbent surface and it attributes to rapider REE adsorption on MIL-101-PMIDA than on1,4-PA-SBA. Lu adsorption capacity was 2.5 times higher than Y due to its superior ion-exchange capability with grafted phosphonic groups. Both adsorbents retained over 90% of adsorption capacity after 5 adsorption/desorption cycles which demonstrate the high structural stability of the materials.

A Theoretical Investigation: Effect of Structural Modifications on Molecular, Electronic, and Optical Properties of Phosphonate Substituted BODIPY Dyes

AbstractPhosphonates are important organophosphorus compounds which exhibit versatile properties in organic chemistry, medicinal chemistry, materials and biological applications. Phosphonate groups have appeared in a very few examples of BODIPY (4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene) compounds that are important florescent dyes in these areas. The deficiency in the area motivated us to investigate how the phosphonate substituent(s) affect the structural, electronic, and optical properties of meso, α, or α, α′‐substituted BODIPYs using density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) methods. We have identified the suitable method as HSEH1PBE functional in combination with the basis set 6‐31+G** by comparing the theoretical results with the experimental studies. Structural, electronic and optical parameters of a series of designed phosphonate substituted 12 BODIPYs (1‐4) have been investigated. The α, and α, α′‐vinyl phosphonate substituted BODIPYs (3,4) compared to meso‐substituted BODIPYs (1,2) have both lower HOMO/LUMO electronic energies [(−5.57)‐(−6.19)/(−3.16)‐(−3.91)] and lower electronic energy gaps (Egap) (2.11–2.42). Electrostatic potential analysis was performed for all BODIPYs to characterize their electron distribution and TD‐DFT analysis was used for the absorption spectral analysis. The presented theoretical approach can be a practical guide for experimental studies for the design of new BODIPY compounds with desired properties.

Functionalized aminophosphonate chitosan-magnetic nanocomposites for Cd(II) removal from aqueous solutions: Performance and mechanisms of sorption

Functionalized magnetic nanocomposites have recently retained a great attention for metal recovery from aqueous solutions. In this work, two magnetic-chitosan nanocomposites are synthesized by grafting α-aminophosphonate functions (i.e., methyl- and phenyl-aminophosphonate, Me-MCS and Ph-MCS, respectively) using a facile two-steps process. The physicochemical properties of these nanocomposites are characterized including nano-structure characterization (TEM), magnetic properties (VSM), crystallinity (XRD), and chemical characterization (elemental CHNP analysis, FTIR, XPS and TGA). FTIR and XPS analyses confirm the contribution of amine and phosphonic groups in the binding of cadmium ions. These materials are extensively investigated for Cd(II) removal: maximum sorption capacities reach 118.1 mg g−1 for Me-MCS and 193.5 mg g−1 for Ph-MCS, at the optimum pH (in the range pH 6–7); and the sorption isotherms are fitted by the Langmuir model. Small-size particles allow achieving fast uptake (within 2 h of contact); and kinetic profiles are appropriately modeled by the PSORE (pseudo-second order rate equation) and the Crank equation (for resistance to intraparticle diffusion). Cadmium sorption is exothermic. The metal is efficiently desorbed using 0.5 M acidified thiourea solution and the sorbent can be recycled for a minimum of five cycles (loss in sorption and desorption performances around 20% at the fifth cycle). In multi-component solutions the two sorbents show some differences in selectivity profiles, which can be roughly correlated with the hard/soft characteristics of reactive groups and the softness properties of heavy metal ions. The sorbents are successfully used for Cd(II) removal from a water sample obtained from Al-Burullus Lake (Kafr-El-Sheikh Governorate, Egypt).

Modulating MnO2 Interface with Flexible and Self-Adhering Alkylphosphonic Layers for High-Performance Zn-MnO2 Batteries.

Metal oxides are essential electrode materials for high-energy-density batteries, but it remains highly challenging to modulate their interfacial charge-transfer process and improve their cycling stability. Here, using MnO2 nanofibers as an example, we describe the application of self-assembled alkylphosphonic modification layers for significantly improved cycling stability and high-rate performance of Zn-MnO2 batteries. Two modifier organic molecules with the same phosphonic functional group but different alkyl tail lengths were employed and systematically compared, including butylphosphonic acid (BPA) and decylphosphonic acid (DPA). The phosphonic groups form strong interfacial covalent bonding and assist the generation of conformal and flexible coatings with few nanometers thickness on a MnO2 surface. The intertwined alkylphosphonic molecules in the modulation layers have interconnected phosphonic groups, which improve interfacial charge transfer of H+ ions for fast conversion of MnO2 to MnOOH without compromising electrolyte wetting. Importantly, the coating layers effectively reduce dissolutive loss of Mn2+ from MnO2 during battery cycling since diffusion of both water molecules and divalent Mn2+ cations was inhibited across the modification layers. The flexible coatings could readily adapt to the morphological changes of MnO2 during battery cycling and provide long-lasting protection. Overall, we identified that BPA has the optimal balance of hydrophobic-hydrophilic components and enabled modified MnO2 cathodes with >30% improved discharge capacity compared with unmodified MnO2 cathodes, together with substantially improved long-term cycling stability with >60% capacity retention for 400 cycles in aqueous ZnSO4 electrolytes without any Mn2+ additive. This work provides new insights into tuning electrochemical pathways that move away from the prevailing rigid, ceramic coating-based surface modifications.

Synthesis, Characterization, and Simulation of Four-Armed Megamolecules.

This paper describes the synthesis, characterization, and modeling of a series of molecules having four protein domains attached to a central core. The molecules were assembled with the "megamolecule" strategy, wherein enzymes react with their covalent inhibitors that are substituted on a linker. Three linkers were synthesized, where each had four oligo(ethylene glycol)-based arms terminated in a para-nitrophenyl phosphonate group that is a covalent inhibitor for cutinase. This enzyme is a serine hydrolase and reacts efficiently with the phosphonate to give a new ester linkage at the Ser-120 residue in the active site of the enzyme. Negative-stain transmission electron microscopy (TEM) images confirmed the architecture of the four-armed megamolecules. These cutinase tetramers were also characterized by X-ray crystallography, which confirmed the active-site serine-phosphonate linkage by electron-density maps. Molecular dynamics simulations of the tetracutinase megamolecules using three different force field setups were performed and compared with the TEM observations. Using the Amberff99SB-disp + pH7 force field, the two-dimensional projection distances of the megamolecules were found to agree with the measured dimensions from TEM. The study described here, which combines high-resolution characterization with molecular dynamics simulations, will lead to a comprehensive understanding of the molecular structures and dynamics for this new class of molecules.

Complex character of the influence of polycarboxylic and phosphonic acids on the crystallization of calcium and magnesium salts in dynamic conditions

The influence of water-soluble organic compounds (adipic, polyaspartic and phosphonic acids) and their compositions on the crystallization of calcium and magnesium salts in dynamic conditions has been studied. It is found that the induction period of phase formation increases in the presence of polyaspartic and phosphonic acids 2.3–5.2 times in the range of their content from 0.05 to 0.2 ppm. The results of XRD and electron microscopic studies confirm the change in the phase composition and morphology of the crystalline precipitate that is formed. The dibasic carboxylic acid influence on the induction period, composition and structure of the precipitate is much less. It is established that the composition of organic acids also increases the induction period of phase formation. The complex inhibitor provides an increase in the critical supersaturation level in the system. The phosphonic and carboxyl groups of the inhibitor interact with calcium and magnesium ions and block the crystallization nuclei. When interacting with the dicarboxylic acid and polyacid adsorption on the surface of the formed crystals, the microcrystals dissolve.

ZrCl4-catalyzed nucleophilic dearomatization of 2-hydroxy-pyrimidines: A concise synthesis of novel 3,4-dihydropyrimidin-2(1H)-ones containing a phosphonic ester group

Catalytic nucleophilic dearomatization of 2-hydroxypyrimidines with phosphites was effectively achieved by utilizing ZrCl4 as the catalyst under mild conditions. This new methodology presents a direct synthesis of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) from readily accessible 2-hydroxypyrimidine derivatives. Various of mono-substituted, di-substituted and tri-substituted 2-hydroxypyrimidines underwent a nucleophilic dearomatization to furnish a kind of novel phosphonic ester-containing DHPMs unreported before in high yields.

Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells

Summary Understanding defects is of paramount importance for the development of stable halide perovskite solar cells (PSCs). However, isolating their distinctive effects on device efficiency and stability is currently a challenge. We report that adding the organic molecule 3-phosphonopropionic acid (H3pp) to the halide perovskite results in unchanged overall optoelectronic performance while having a tremendous effect on device stability. We obtained PSCs with ∼21% efficiency that retain ∼100% of the initial efficiency after 1,000 h at the maximum power point under simulated AM1.5G illumination. The strong interaction between the perovskite and the H3pp molecule through two types of hydrogen bonds (H…I and O…H) leads to shallow point defect passivation that has a significant effect on device stability but not on the non-radiative recombination and device efficiency. We expect that our work will have important implications for the current understanding and advancement of operational PSCs.

Effect of phosphonate functional group on corrosion inhibition of imidazoline derivatives in acidic environment

In the present study, ({2-[2-(7-Isopropyl-1,4-dimethyl-9,10-octahydro-phenanthren-1-yl)-4,5-dihydro-1-yl]-ethylamino}-methyl)-phosphonicimidazole (GSIM) was synthesized by introducing phosphonate (–PH2O3) group into imidazoline derivatives and its corrosion inhibition performance was studied for Q345 steel in acidic medium along with SIM using potentiodynamic polarization, EIS and SECM analysis. Surface analysis of steel samples was also performed by optical microscopy and SEM-EDS analysis after polarization tests. XPS was used to detect chemical composition of the surface passive films. It was observed that introducing -PH2O3 group not only improved the adsorption capacity on the metal surface by coordinating with iron ions, but also inhibited the interference of hydrogen bond formed by –NH2 group and water molecules on the adsorption. GSIM not only inhibited intercrystalline corrosion and pitting corrosion, but also reduced uniform corrosion. Thermodynamics studies demonstrated that GSIM followed the Langmuir adsorption isotherm and had a larger adsorption equilibrium constant than SIM, which indicated that it had a stronger adsorption capacity. XPS and UV confirmed that the coordination between GSIM and Fe3+ and hydrogen bonding between SIM and water molecules. The quantum chemical study further clarified that the site and strength of hydrogen bond between SIM and H2O and the dominant configuration and coordination stability of GSIM with Fe3+.

Nucleotide analogues containing a pyrrolidine, piperidine or piperazine ring: Synthesis and evaluation of inhibition of plasmodial and human 6-oxopurine phosphoribosyltransferases and invitro antimalarial activity.

Parasites of the Plasmodium genus are unable to produce purine nucleotides de novo and depend completely on the salvage pathway. This fact makes plasmodial hypoxanthine-guanine-(xanthine) phosphoribosyltransferase [HG(X)PRT] a valuable target for development of antimalarial agents. A series of nucleotide analogues was designed, synthesized and evaluated as potential inhibitors of Plasmodium falciparum HGXPRT, P.vivax HGPRT and human HGPRT. These novel nucleoside phosphonates have a pyrrolidine, piperidine or piperazine ring incorporated into the linker connecting the purine base to a phosphonate group(s) and exhibited a broad range of Ki values between 0.15 and 72μM. The corresponding phosphoramidate prodrugs, able to cross cell membranes, have been synthesized and evaluated in a P.falciparum infected human erythrocyte assay. Of the eight prodrugs evaluated seven exhibited invitro antimalarial activity with IC50 values within the range of 2.5-12.1μM. The bis-phosphoramidate prodrug 13a with a mean (SD) IC50 of 2.5±0.7μM against the chloroquine-resistant P.falciparum W2 strain exhibited low cytotoxicity in the human hepatocellular liver carcinoma (HepG2) and normal human dermal fibroblasts (NHDF) cell lines at a concentration of 100μM suggesting good selectivity for further structure-activity relationship investigations.

Synthesis of Phosphonomethylated Bromoacetylfurans and Their\t\t\tReactions with 1,3-Dicarbonyl Compounds

Bromination of (diethoxyphosphorylmethyl)acetylfurans with dioxane dibromide\t\t\t\t\tin the mixture of chloroform and acetic acid in presence of traces of hydrogen\t\t\t\t\tbromide at room temperature proceeds selectively at the methyl group of ketone\t\t\t\t\tdoes not involving phosphonate group. Obtained bromoacetyl derivatives were used\t\t\t\t\tfor alkylation of acetoacetic ester and cyclohexan-1,3-dione. Reaction of\t\t\t\t\t1,4-diketone prepared from acetoacetic ester with hydrazine hydrate in ethanol\t\t\t\t\tat room temperature leads to formation of furylpyrazines due to aromatization of\t\t\t\t\tintermediate azines by means of air oxygen.

A convenient one-pot synthesis of novel functionalized thiophene, thieno[2,3-b] thiophene, thiopyran, and thiopyrano[2,3-b]thiopyran bearing phosphonate groups

ABSTRACT Design of some novel functionalized thiophene, thieno[2,3-b]thiophene, thiopyran and thiopyrano[2,3-b]thiopyran bearing phosphonate groups was described in one-pot through simple two steps. The methodology depended on the reaction of three-component of chloroacetyl chloride with triethyl phosphite in the presence of sodium 2,2-dicyanoethene-1,1-bis(thiolate) or sodium (2,2-dicyano-1-methylthioethen-1-yl)thiolate in a certain sequence.

Phosphorylation of Guar Gum/Magnetite/Chitosan Nanocomposites for Uranium (VI) Sorption and Antibacterial Applications.

The development of new materials is needed to address the environmental challenges of wastewater treatment. The phosphorylation of guar gum combined with its association to chitosan allows preparing an efficient sorbent for the removal of U(VI) from slightly acidic solutions. The incorporation of magnetite nanoparticles enhances solid/liquid. Functional groups are characterized by FTIR spectroscopy while textural properties are qualified by N2 adsorption. The optimum pH is close to 4 (deprotonation of amine and phosphonate groups). Uptake kinetics are fast (60 min of contact), fitted by a pseudo-first order rate equation. Maximum sorption capacities are close to 1.28 and 1.16 mmol U g−1 (non-magnetic and magnetic, respectively), while the sorption isotherms are fitted by Langmuir equation. Uranyl desorption (using 0.2 M HCl solutions) is achieved within 20–30 min; the sorbents can be recycled for at least five cycles (5–6% loss in sorption performance, complete desorption). In multi-component solutions, the sorbents show marked preference for U(VI) and Nd(III) over alkali-earth metals and Si(IV). The zone of exclusion method shows that magnetic sorbent has antibacterial effects against both Gram+ and Gram- bacteria, contrary to non-magnetic material (only Gram+ bacteria). The magnetic composite is highly promising as antimicrobial support and for recovery of valuable metals.

A facile and durable flame retardant approach for silk fabric through Kabachnik-Fields reaction

This study facilely developed the durable flame retardant (FR) silk fabric by bonding phosphonate groups to silk fiber through Pudovik addition of diethyl phosphite onto Schiff base aldehyde-amine intermediate, namely Kabachnik-Fields reaction. The cross-linking mechanism between FR agent and silk fiber, the thermal resistance, FR ability and durability, and FR mechanism of the modified silk were studied. The modified silk had increased thermal resistance. The modified silk fabric with diethyl phosphite over 13.8 g/L had the self-extinguishing ability and obtained the char length of lower than 11.0 cm and LOI value of higher than 27.4 %, suggesting high FR ability of the modified silk. The modified silk also reached self-extinction after 15 robust launderings, which should be attributed to the covalent cross-linking of phosphonate groups onto silk fiber. The char residue analyses suggested a condensed charring FR mechanism for the modified silk. The Pudovik addition of diethyl phosphite onto silk macromolecular participated Schiff base intermediate shows great possibility to act as effective and durable FR strategy for silk textile.