Gas Phase Research Articles

Experimental molecular structures in the gas phase at the upper size limit: The case of Si6Tip6.

Currently, the largest (ramax = 19.9Å) and by far the most complicated (234 atoms, C1 symmetry, 696 independent geometrical parameters, and 27 261 interatomic terms) experimental molecular structure of a cage-type Si6Tip6 (Tip = 2,4,6-iPr3C6H2) isomer has been investigated in the gas phase by the electron diffraction method (Tav = 645K) supplemented with theoretical simulations. A detailed analysis of the current possibilities for experimentally investigating large molecular structures is performed. A series of density functional theory approximations and the role of dispersion interactions have been benchmarked using the obtained data. Based on the refined geometry of Si6Tip6, various quantum-chemical methods have been applied for the investigation of the electronic structure of its Si6 core. In particular, natural bond orbital, quantum theory of atoms in molecules, interacting quantum atoms, fractional occupation number weighted density, and complete active space self-consistent field (CASSCF) methods were utilized. The diradical character of the molecule has been assessed by the UHF and CASSCF approximations. The problem of bonding between the hemispheroidal silicon atoms has been investigated.

Universal intumescent polyelectrolyte complex treatment for cotton, polyester, and blends thereof

Inhibiting the flammability of natural, synthetic, and blended textiles with a single treatment is challenging because of differing fiber properties and chemistries. Intumescent surface treatments that promote char formation can be applied in the form of a polyelectrolyte complex (PEC) containing nitrogen and phosphorus compounds that combat burning in both the condensed and gas phase. Poly(allylamine hydrochloride) (PAH) and poly(sodium phosphate) (PSP) comprise a PEC that reduces the flammability of cotton, polyester, and polyester/cotton (PECO). The incorporation of melamine renders each substrate self-extinguishing. The degradation of PAH is seen to differ between substrates, with gas phase degradation being more prevalent on polyester and heterocyclization occurring on cellulose. Quantitatively, cotton flammability is reduced more than that of polyester, but significant improvements are made to the char yield, heat release, and volatile emission for all fabric types. This water-based coating is rapidly applied in two steps for fire protection. These results demonstrate the versatility of PEC coatings as environmentally-benign fire protection for a variety of chemistries.

Effect of dissolved KOH and NaCl on the solubility of water in hydrogen: A Monte Carlo simulation study.

Vapor-Liquid Equilibria (VLE) of hydrogen (H2) and aqueous electrolyte (KOH and NaCl) solutions are central to numerous industrial applications such as alkaline electrolysis and underground hydrogen storage. Continuous fractional component Monte Carlo simulations are performed to compute the VLE of H2 and aqueous electrolyte solutions at 298-423K, 10-400bar, 0-8 molKOH/kg water, and 0-6 molNaCl/kg water. The densities and activities of water in aqueous KOH and NaCl solutions are accurately modeled (within 2% deviation from experiments) using the non-polarizable Madrid-2019 Na+/Cl- ion force fields for NaCl and the Madrid-Transport K+ and Delft Force Field of OH- for KOH, combined with the TIP4P/2005 water force field. A free energy correction (independent of pressure, salt type, and salt molality) is applied to the computed infinite dilution excess chemical potentials of H2 and water, resulting in accurate predictions (within 5% of experiments) for the solubilities of H2 in water and the saturated vapor pressures of water for a temperature range of 298-363K. The compositions of water and H2 are computed using an iterative scheme from the liquid phase excess chemical potentials and densities, in which the gas phase fugacities are computed using the GERG-2008 equation of state. For the first time, the VLE of H2 and aqueous KOH/NaCl systems are accurately captured with respect to experiments (i.e., for both the liquid and gas phase compositions) without compromising the liquid phase properties or performing any refitting of force fields.

Flame retarded lignin-based epoxy resin with excellent antibacterial and anti-corrosion properties modified by coordinated phospho-nitrogen flame retardant

In this paper, epoxidized lignin (HL) and sebacic acid (HSA) were used as the hard and soft segments, respectively, and a kind of reactive coordinated phosphorous-nitrogen flame retardants (DTZ) was designed and synthesized via Zn2+ coordination to fabricate a multifunctional non-bisphenol A lignin based epoxy (EP) composite. The swelling behavior and morphological analysis demonstrated that the crosslinking density of EP increased significantly after adding HL and DTZ. The existence of coordination sacrificial bond of DTZ dissipated more energy when it was subjected to external forces, thereby making 80HSA/14HL/6DTZ maintained a high tensile strength (10.65 MPa) while having little damage to the elongation at break (30.74 %). The limiting oxygen index (LOI) of 80HSA/14HL/6DTZ was significantly higher than that of 100HSA (22.3 %), reaching 36.6 %, and the vertical combustion test (UL-94) reached V-0 level. The morphology of carbon layer and residual carbon analysis showed that HL and DTZ had synergistic effect, and the flame retardancy mechanism of gas phase and condensed phase existed in the combustion process. Simultaneously, the addition of HL and DTZ also endowed the EP composite with excellent corrosion resistance and antibacterial properties.

Numerical Development of a Thermal Pre-processing Step for the Recycling of Lithium-Ion Batteries

AbstractIn the present study, a numerical model is being developed to simulate a step in the battery recycling chain, namely the thermal pre-treatment process. This process involves exposing battery cells to a high-temperature environment to induce a thermal runaway, with the aim of maximising the recovery of valuable metals in the subsequent downstream recycling steps. The proposed numerical model utilises the CFD-DEM framework. Computational Fluid Dynamics (CFD) is used to calculate the gas phase variables. The battery is considered a solid phase, using the Discrete Element Method (DEM) to model its behaviour under high temperature. In this context, an experiment was designed to reproduce conditions similar to a battery thermal deactivation process. Once elaborated, the results from the experiments are compared to the numerical model, seeking further simulations using more realistic furnace designs.

Fabrication of Flame-Retardant Ammonium Polyphosphate Modified Phytic Acid-Based Rigid Polyurethane Foam with Enhanced Mechanical Properties

Ammonium polyphosphate (APP) and self-made nickel phytate (PANi) were used as modified materials to prepare green biomass rigid polyurethane foam (RPUF). The flame retardancy, thermal stability, smoke toxicity and mechanical properties of the modified RPUF were investigated by limiting oxygen index (LOI), a cone calorimetry (CONE) test, thermogravimetric analysis and a compression test. The results showed that the RPUF with 10 wt% APP (PANi/APP10) had the highest LOI of 26.5%. Its peak heat release rate (PHRR) and total heat release (THR) were reduced by 29.64% and 24.05% compared with PANi/APP0 without APP. And its smoke production rate (SPR) and total smoke release (TSR) decreased by 33.14% and 19.88%, respectively. Compared with pure RPUF, the compressive strength of PANi/APP10 was increased by 50%, mainly because APP itself was an ultra-fine powder, which was better compatible with the matrix and improved the hardness of the material. The results showed that the synergistic effect of the gas phase and the condensed phase mechanism could effectively improve the flame-retardant effect. The current research results provided a new strategy for the preparation of green and low-toxicity RPUF.

Recent Development of Physical Hydrogen Storage: Insights into Global Outlook and Future Applications.

Transition of global energy market towards an environment-friendly sustainable society requires a profound transformation from fossil fuel to zero carbon emission fuel. To cope with this goal production ofrenewable energy is accelerating worldwide. Research in renewable energy from production and storage to practical utilization requires an organized approach. One of the best renewable energy carrier is the hydrogen, due to its clean combustion and abundance. Nonetheless, its storage is a critical challenge to its success. Hydrogen must be stored long after being produced and transported to a storage site. Physical hydrogen storage is vital among hydrogen storage modes, and its shortcoming needs to overcome for its successful and economic benefits. This review intends to discuss the techniques and applications of physical hydrogen storage in the state of compressed gas, liquefied hydrogen gas, and cold/cryo compressed gas concerning their working principle, chemical and physical properties, influencing factors for physical hydrogen storage, and transportation, economics, and global outlook. Insights of several probable physical hydrogen storage (PHS) systems are highlighted. The outcomes of this review envisioned that the PHS still necessitates technological advancements despite having remarkable success. The Liquid Hydrogen Gas storage marks better sustainability than Compressed and Cryo Compressed Gas. The physical hydrogen storage method can store hydrogen in tanks in any state (liquid or gas) under 20 K for the liquid state and ambient temperature for the gaseous state The Bibliographic analysis depicts that the research in hydrogen rising with time and mostly the research in conducted in USA with 231 articles. Prospects and challenges with lessons learned and the limitation opens the door to further research, which would be helpful for efficient and long-term physical hydrogen storage.

Fluorescence of BODIPY dyes in gas phase at near-ambient conditions

Molecular fluorescence is a phenomenon that is usually observed in condensed phase. It is strongly affected by molecular interactions. The study of fluorescence spectra in gas-phase can provide a nearly ideal model for the evaluation of the intrinsic properties of fluorophores. Unfortunately, most conventional fluorophores are not volatile enough to allow for the study of their fluorescence in gas phase. Here we report very bright gas phase fluorescence of simple BODIPY dyes that can be readily observed at atmospheric pressure using conventional fluorescence instrumentation. To our knowledge, this is the first example of visible-range gas-phase fluorescence at near-ambient conditions. Evaporation of the dye in vacuum allowed us to demonstrate organic molecular electroluminescence in gas discharge excited by the electric field produced by a Tesla coil.

Insights into 5-fluorouracil anti–cancer drug encapsulation within the pristine and palladium-doped carbon, silicon-carbide, and germanium-carbide nanotubes: A DFT investigation for advanced nanomedicine applications

In this study, we investigated the interaction and binding properties of 5-Fluorouracil (5-FU), an anti-cancer drug, encapsulated within pristine and palladium-doped carbon, silicon-carbide, and germanium-carbide nanotubes (CNT, SiCNT, GeCNT). Using density functional theory (DFT), we conducted a comprehensive analysis at both aqueous and gas phases. This included geometrical, structural, electrical, bonding, and thermodynamic properties, optimized geometries, adsorption energies, quantum molecular descriptors, frontier molecular orbitals, and topological parameters at the M06-2X level of theory. Our findings indicate that Pd-doping enhances the encapsulation capabilities of nanotubes, strengthening interactions with 5-FU and improving water solubility. Calculations of recovery time required for drug release suggest that Pd-doped nanotubes effectively control the release of 5-FU. Notably, the decapsulation time of 5-FU from of Pd-doped nanotubes was longer in the gas phase than in aqueous conditions. Using the quantum theory of atoms in molecules (QTAIM) method, we investigated intermolecular interactions and critical bonding points. Natural bond orbital (NBO) analysis revealed enhanced stabilization of the 5-FU molecule post-encapsulation, with charge transfer primarily directed from nanotubes to the 5-FU. Hirshfeld surface analysis highlighted that hydrogen bonds between 5-FU active sites and nanotubes are crucial in encapsulation and fixation. Reduced Density Gradient (RDG) analysis confirmed Pd-doping as a primary source of strong attractive interactions in 5-FU/Pd-doped nanotube complexes compared to pristine nanotubes.

The phase diagram of Mercedes Benz model of water using nested sampling algorithm and molecular dynamics simulations

The Mercedes Benz (MB) model of water is quite popular for explaining the properties of water, but the complete phase diagram has not yet been published. In the MB model, water molecules are modelled as two-dimensional Lennard-Jones discs, with three orientation-dependent hydrogen-bonding arms arranged as in the MB logo. Nested Sampling (NS) is a powerful sampling algorithm for the parameter space that directly calculates the partition function. NS can be used for sampling the equilibrium thermodynamics of atomistic systems and allows access to all thermodynamic quantities in absolute terms, including absolute free energies and absolute entropies. Here, NS is used to calculate the phase diagram of the simple two-dimensional Mercedes-Benz (MB) model of water. 32 water particles were used in NS. While this number of particles provides sufficient agreement with the simulations, the results from fewer particles slowly begin to diverge from the result from NS with 32 particles as some of the equilibrium lines begin to shift. By combining the results from NS and molecular dynamics (MD) simulations, different phases were located and identified. In total, 5 different solid phases, 3 liquid phases and one gaseous phase were observed.

Aspartame and Its Microhydrated Aggregates Revealed by Laser Spectroscopy: Water-Sweetener Interactions in the Gas Phase.

The popular sweetener, aspartame, is an agonist of the tongue's sweet taste receptor. How water molecules affect its conformation or which aspartame atoms are more prone to interact with solvent are helpful questions to understand its activity in different environments. Here, the combination of IR-UV spectroscopic techniques with computational simulations has been successfully applied to characterize aspartame·water0-2 clusters, showing that the addition of water molecules simplifies the conformational panorama of aspartame, favoring the formation of folded structures by interaction with the polar part of the molecule.

Adsorptive dye removal by Cu(II)-modified silica-alumina/polyaniline nanocomposite

The accelerated rate of industrial growth causes a lot of pollutants to be released into the environment. Therefore, the present work aimed at synthesizing a novel and environmentally friendly nanocomposite for eliminating dyes from wastewater. The (silica-alumina13 %)-Cu2+/polyaniline ((Si–Al)–Cu2+/PANI) nanocomposite was synthesized by the oxidative polymerization of aniline in the presence of (Si–Al)–Cu2+ composite. The nanocomposite was characterized by the FT-IR, XRD, BET, SEM, TEM, and EDX techniques. Its surface area was 287.7 m2/g and the pore diameter was 1.92 nm. The pseudo-second-order kinetic and the Langmuir isotherm models offered a satisfactory fit to the adsorption data. The removal percentage of the Acid blue 25 dye (AB25) by the nanocomposite reached 99 % within 60 min at pH 2, while the removal capacity was 135.86 mg/g. Based on the adsorption-desorption cycle results, the efficiency of the nanocomposite (99.7 %) remained unchanged up to the third cycle with a small decrease afterward. To corroborate the experimental results, a molecular modeling study was carried out using the basis function 6–311++G(d,p) and the DFT method to obtain the best molecular structure, physicochemical properties, and spectroscopic spectra of AB25 in the gas phase and water solvent. The electrostatic potential, Fuki functions, natural bond orbital, time-dependent DFT, and theoretical FT-IR were calculated. Furthermore, the adsorption of AB25 on the nanocomposite surface was verified by the Monte Carlo simulations. The computed data correlated well with the experimental results.

Dissolution behavior of mixed calcium‑cobalt carbonates at 25 °C in contact with different gas phases

The potential immobilization of cobalt in various environments can be achieved through the incorporation of Co into carbonate minerals, forming solid solutions of (Ca1-xCox)CO3. However, the thermodynamic properties of these minerals are not well-understood due to conflicting data from natural observations and experiments. In this work, a series of mixed calcium‑cobalt carbonates were prepared and their interaction with aqueous solution was investigated. Depending on the Co/(Ca + Co) mol ratio (XCo) of the mixed solution, ranging from 0.00 to 1.00, pure calcite, Co-bearing calcite, Co-bearing aragonite, Ca-bearing spherocobaltite and pure spherocobaltite were successively synthesized using a precipitation method. Upon dissolution of the Co-bearing solids (XCo = 0.10–1.00) in N2-degassed water (NW) and air-saturated water (AW), the Co concentration of the aqueous solutions increased gradually to a stable state of 0.017–0.191 and 0.018–0.186 mmol/L after 240–360 d dissolution, respectively. When the dissolution occurred in CO2-saturated water (CW), the Co concentration initially spiked to 0.372–2.258 mmol/L within 6 h ∼ 15 d and then decreased to a stable range of 0.030–0.559 mmol/L after 240–360 d. The Co/(Ca + Co) mol ratio in the aqueous solution (XCo2+,AS) was significantly lower than the Co/(Ca + Co) atomic ratio in the solids (XCo,SS), particularly when dissolved in NW and AW. During these dissolution processes in NW, AW and CW at 25 °C, the average log IAP values at the final stable state were determined as follows: for calcite (CaCO3), the values were −8.25 ± 0.03 in NW, −8.34 ± 0.11 in AW, and −8.10 ± 0.08 in CW; for spherocobaltite (CoCO3), they were −9.24 ± 0.26 in NW, −9.39 ± 0.23 in AW, and −9.38 ± 0.09 in CW. Furthermore, the log IAP values increased from those typical for calcite to −7.89 ± 0.01 ∼ −7.84 ± 0.10 for the solid with XCo,SS = 0.187 as XCo,SS increased, eventually aligning with those typical of spherocobaltite. Lippmann diagrams, constructed using the Guggenheim parameters a0 = 2.30 and a1 = 0.265 for the “subregular” calcite-spherocobaltite solid solutions [(Ca1-xCox)CO3] with a miscibility gap ranging from XCo,SS = 0.251 to 0.858, highlighted the “peritectic” point at XCo2+,AS = 0.0538 on the solutus. This analysis revealed that the solids dissolved non-stoichiometrically in water. Consequently, the Co-poor aqueous solution would reach equilibrium with the Co-rich calcite-structure phase at the solid surface.

Femtosecond Core-Level Spectroscopy Reveals Involvement of Triplet States in the Gas-Phase Photodissociation of Fe(CO)5.

Excitation of iron pentacarbonyl [Fe(CO)5], a prototypical photocatalyst, at 266 nm causes the sequential loss of two CO ligands in the gas phase, creating catalytically active, unsaturated iron carbonyls. Despite numerous studies, major aspects of its ultrafast photochemistry remain unresolved because the early excited-state dynamics have so far eluded spectroscopic observation. This has led to the long-held assumption that ultrafast dissociation of gas-phase Fe(CO)5 proceeds exclusively on the singlet manifold. Herein, we present a combined experimental-theoretical study employing ultrafast extreme ultraviolet transient absorption spectroscopy near the Fe M2,3-edge, which features spectral evolution on 100 fs and 3 ps time scales, alongside high-level electronic structure theory, which enables characterization of the molecular geometries and electronic states involved in the ultrafast photodissociation of Fe(CO)5. We assign the 100 fs evolution to spectroscopic signatures associated with intertwined structural and electronic dynamics on the singlet metal-centered states during the first CO loss and the 3 ps evolution to the competing dissociation of Fe(CO)4 along the lowest singlet and triplet surfaces to form Fe(CO)3. Calculations of transient spectra in both singlet and triplet states as well as spin-orbit coupling constants along key structural pathways provide evidence for intersystem crossing to the triplet ground state of Fe(CO)4. Thus, our work presents the first spectroscopic detection of transient excited states during ultrafast photodissociation of gas-phase Fe(CO)5 and challenges the long-standing assumption that triplet states do not play a role in the ultrafast dynamics.

How Solvation Alters the Thermodynamics of Asymmetric Bond-Breaking: Quantum Simulation of NaK+ in Liquid Tetrahydrofuran.

Gas-phase potential energy surfaces (PESs) are often used to provide an intuitive understanding of molecular chemical reactivity. Most chemical reactions, however, take place in solution, and it is unclear whether gas-phase PESs accurately represent chemical processes in solvent environments. In this work we use quantum simulations to investigate the dissociation energetics of NaK+ in liquid tetrahydrofuran (THF) to understand the degree to which solvent interactions alter the gas-phase picture. Using umbrella sampling and thermodynamic integration techniques, we construct condensed-phase free energy surfaces of NaK+ on THF in both the ground and electronic excited states. We find that solvation by THF completely alters the nature of the NaK+ bond by reordering the thermodynamic dissociation products. Reaching the thermodynamic dissociation limit in THF also requires a long-range charge transfer process that has no counterpart in the gas phase. Gas-phase PESs, even with perturbations, cannot adequately describe the reactivity of simple asymmetric molecules in solution.

Gas/particle partitioning of PCDD/Fs: Distributions and implications for available models

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) are semi-volatile organic compounds (SVOCs) existing in the atmosphere in the gas and particulate phase, remain persistent for a long time and pose a high risk to the environment and human health. In this study, PCDD/F measurements were made in an urban area between June 2022 and April 2023. In order to understand the fate of PCDD/Fs, the gas/particle (G/P) partitioning was studied. Although various models have been developed to determine the G/P partitioning of SVOCs, only logKp-logPL0, Junge-Pankow and Harner-Bidleman models are generally used for PCDD/Fs. In this study, nine different models (Junge-Pankow, Harner-Bidleman, Dachs-Eisenreich, Li-Ma-Yang, pp-LFER, mp-pp-LFER, QSPR, logKp-logPL0, logKp-logKOA) were employed to determine the G/P partitioning. To the best of our knowledge, pp-LFER, mp-pp-LFER and QSPR models were evaluated for PCDD/Fs for the first time in this study. In addition, the performance of the models within the equilibrium (EQ), non-equilibrium (NE) and maximum partitioning (MP) domain was investigated for PCDD/Fs for the first time in this study. Accordingly, models based on absorption in the EQ domain, adsorption in the NE domain and adsorption and absorption mechanisms in the MP domain were found to be effective in explaining the G/P transitions. It was determined that there is no equilibrium situation in the G/P partitioning. The Junge-Pankow, pp-LFER, Li-Ma-Yang and QSPR models under-predicted the particle fraction values while the other models showed a high prediction profile. The Li-Ma-Yang model showed the closest results to the measured particle fraction values, and it determined that deposition mechanisms are of non-negligible importance in the G/P partitioning of PCDD/Fs. One of the new models, the pp-LFER model, has shown remarkable success at high logKOA values. The mp-pp-LFER model, which overestimated the contribution of the adsorption mechanism, showed a very high prediction profile compared to the measured values.

A sprinkler- water cycle PEC-MFC system with bimetallic monatomic Co-Fe/g-C3N4/ACF cathode achieves efficient removal of gas trimethylamine

Volatile organic compounds (VOCs) air pollutants are the precursors of ozone and PM2.5, all harmful to human health. To reduce the equipment volume further and improve the treatment capacity at room temperature, a novel microbial fuel cell (MFC) system, with a sprinkler and water recycle module, was designed to integrate bio-electricity generation from biodegradation and photocatalytic oxidation of VOCs over cathodic diatomic Co-Fe/g-C3N4 doped activated carbon felt (Co-Fe/g-C3N4/ACF). The removal of trimethylamine in both the gas and liquid phase was proved (VOCs concentration in air ≈ 0.93 g m−3, the removal capacity reached ≥ 119.97 mg gcat-1h−1). Through the sprinkler-water cycle, the trimethylamine molecules in air transferred and diffused to the liquid phase, then acted as the only carbon source for the electrogenic bacteria, that supplied the electricity to drive photoelectric catalysis under light illumination. The high efficiency (>2086 mg gcat-1h−1) and low energy consumption in the new system at room temperature means broad application prospect in VOCs treatment.

Mechanism and application of gas phase trapping by spontaneous imbibition

For fractured gas reservoirs with strong water drive, gas phase trapping affects the gas recovery significantly. The recovery may be less than 50% for some reservoirs while it is only 12% for Beaver River gas field. The gas phase trapping mechanism has been revealed by the results of depletion experimental test. The residual pressure of the trapped gas is as high as 11.75 MPa with a 12.8 cm imbibition layer resulting in gas recovery deceased 49.5% compared with that without imbibition layer. A mathematical model is built to calculate the imbibition thickness based on capillary pressure and relative permeability of the matrix. The gas phase trapping are analyzed by two representative wells in Weiyuan gas field, the intermittent production reinforces the imbibition thickness and result in gas trapped in the matrix block with high residual pressure for the low performace gas wells, the extremely low gas recovery can be explained more rationally. That lays a foundation of improving the gas recovery for fractured reservoirs.

Minimal model for chirally induced spin selectivity: spin-orbit coupling, tunneling and decoherence

Here we review a universal model for chirally induced spin-selectivity (CISS) as a standalone effect occurring in chiral molecules. We tie together the results of forward scattering in the gas phase to the results for photoelectrons in chiral self-assembled monolayers, and the more contemporary results in two terminal transport setups. We discuss the ingredients that are necessarily present in all experiments to date, which we identify as: (i) chirality, be it point, helical or configurational, (ii) the spin–orbit coupling as the spin active coupling of atomic origin, (iii) decoherence as a time-reversal symmetry breaking mechanism that avoids reciprocity relations in the linear regime and finally (iv) tunneling that accounts for the magnitude of the spin polarization effect. This proposal does not discard other mechanisms that can yield comparable spin effects related to interactions of the molecule to contacts or substrates that have been proposed but are less universal or apply to specific situations. Finally, we discuss recent results suggesting CISS as a molecular phenomenon in the realms of enantiomer selectivity, coherent electron transfer, and spin effects in chiroptical activity.

Elemental synergy flame retardant effect of Schiff base derivatives with similar chemical structure in TPU

To investigate the synergistic flame retardant effect of various elements, three flame retardants (SMAE, SDPS, SDPB) with similar chemical structure and containing different flame retardant elements were designed, synthesized, and applied to TPU. The test results showed that SMAE had a phosphorus-nitrogen synergistic effect and primarily exerted its flame retardant effect in the gaseous phase. The limiting oxygen index value of the TPU/4SMAE reached 32% and passed UL 94 V-0 rating test. SDPB was obtained by introducing the boron, which further enhanced the flame retardant effect in the gaseous phase. The thermogravimetric combined with Fourier transform infrared spectroscopy results showed that TPU/4SDPB had the lowest intensity of gaseous phase products. With only 2wt.% SDPB, TPU can pass UL 94 V-0 test. Therefore, it also demonstrated that there was a good synergy between boron and phosphorus and nitrogen. SDPS was obtained by introducing the silicon, which can exert the flame retardant effect in the condensed phase. Scanning electron microscopy results showed that char layer of TPU/SDPS was the densest and silicon was retained as Si-O and Si-C in the char layer. However, the gaseous phase flame retardant effect of SDPS was restrained, and TPU/4SDPS only passes the V-2 rating. Hence, this work provided the direction of Schiff base derivatives flame retardants structure design in TPU.