Triazine-based Frameworks Research Articles

The preparation of layered double hydroxide wrapped with triazine-based organic framework to enhance the flame retardancy for polypropylene

Layered double hydroxide (LDH) can be used as a flame retardant (FR) for polypropylene (PP) because of its excellent flame retardancy and smoke-suppression effects. However, the agglomeration of LDH seriously affects its dispersity in the PP matrix, thus limiting its application as a FR polymer. This study aimed to enhance the dispersion of LDH in the PP matrix for improving its flame retardancy performance. Herein, a reactive triazine-based organic framework (TOF) was designed and formed by the in situ polymerisation of cyanuric chloride and melamine, and then the LDH surface was covered with TOF to obtain a novel core–shell FR (LDH@TOF), with TOF as the ‘shell’ and LDH as the ‘core’. Subsequently, LDH@TOF was melted into the PP matrix as nanofillers to prepare PP and LDH@TOF composites (PP/LDH@TOF). As expected, the PP/LDH@TOF composites exhibited superior flame-retarding performance (limiting oxygen index of 29.2% and UL-94 V-0 rating) and favourable smoke-suppression performance at 20 wt% of LDH@TOF loading. Moreover, the peak heat release rate, total heat release and total smoke production of PP/LDH@TOF composites decreased by 29.9%, 12.1% and 12.4%, respectively, compared with those of PP and LDH composites. The outstanding flame retardancy properties of the PP/LDH@TOF composites were attributed to the better dispersibility of LDH@TOF in the PP matrix, the synergy of the physical barrier effect of nanosheets and the dense carbonisation acceleration of LDH@TOF. The findings of this study provide a highly efficient approach for functionalising LDH for expanding its application value of PP composites.

First principles study of a triazine-based covalent organic framework as a high-capacity anode material for Na/K-ion batteries.

The rational design of high-performance anode materials is crucial for the development of rechargeable Na-ion batteries (NIBs) and K-ion batteries (KIBs). In this study, based on density functional theory (DFT) calculations, we have systematically investigated the possibility of a bilayer triazine-based covalent organic framework (bilayer TCOF) as an anode for NIBs and KIBs. The calculation of the electronic band structure shows that the bilayer TCOF is a direct band gap semiconductor with a band gap of 2.01 eV. After the adsorption of Na/K at the most favorable sites, the bilayer TCOF transitions from a semiconductor to a metal state, guaranteeing good electronic conductivity. The low diffusion barriers of the bilayer TCOF are 0.45 and 0.26 eV, respectively, indicating a fast diffusion rate of Na/K ions. In addition, the bilayer TCOF has a theoretical storage capacity of up to 628 mA h g-1. Finally, it is found that the average voltage of the bilayer TCOF for NIBs and KIBs is 0.53 and 0.48 V, respectively. Based on these results, we can conclude that the bilayer TCOF may be a suitable anode material for NIBs and KIBs.

Microwave-assisted synthesis of triazine covalent organic frameworks via friedel-crafts reaction for use in treating brackish Water

Water scarcity is becoming an ever-growing problem in society. This is all due to the rapid increase in human population, harsh changes in the weather climate. New approaches for treating and recycling brine water into freshwater instead of discharging are needed, significantly large reduction in energy usage and decreasing harmful impact to the environment must be achieved in brine recovery. This study aims to introduced green technology into the reclamation of brine water by use of covalent organic frameworks (COFs) materials which will be used as part of a novel triazine-based COFs material which can be used as a nanomembrane for desalination of brine water from water treatment plants at Umgeni Water. Current technological approaches used are inefficient and unsuitable in 3rd world, developing countries including the republic of South Africa. This work focuses on a microwave-assisted synthesis involving Friedel Crafts reaction between monomers to yield a product of a triazine-based covalent organic frameworks (COFs) membranes. To confirm the products high resolution transmission electron microscopy (HRTEM), carbon NMR (13C NMR) with peaks at chemical shifts of 131, 143 and 172 ppm respectively. Fourier-transform infrared spectroscopy (FTIR) was employed and showed N-H stretches at a region of 3396 to 3050 cm-1. The COFs that were successfully synthesised are going to be incorporated on a polymeric substrate to fabricate a nanofiltration membrane and applied for nanofiltration or ultrafiltration purposes.

Characterization of a conjugate between poly(N-vinyl caprolactam) and a triazine-based covalent organic framework as a potential biomaterial.

Thermoresponsive polymers (TRPs) have been explored over decades for biomedical applications, and poly(N-vinylcaprolactam) (PVCL) TRP is extensively investigated due to its low toxicity and lower critical solution temperature (LCST), close to physiological temperatures. Besides this, the utilization of covalent organic frameworks (COFs), which belong to a class of porous polymers, in bio-based applications is of great interest due to their remarkable properties. Thus, the integration of PVCL and covalent organic frameworks (COFs) as conjugate materials can lead to advanced bio-based applications; however, the need is to understand the influence of the COF on the PVCL conformation. Herein, a triazine-based COF, CC-TAPT-COF, has been synthesized and completely characterized. Later, the effect of CC-TAPT-COF on the PVCL polymer conformation was studied using various techniques. In fluorescence spectroscopy, a fluorescence quenching for PVCL in the presence of CC-TAPT-COF was observed, which indicated conformational changes. Later, results from thermal fluorescence studies and dynamic light scattering as a function of temperature showed a slight decrease in LCST value for PVCL after the addition of CC-TAPT-COF concentrations. These results showed a slight effect of CC-TAPT-COF on the PVCL conformation. Likewise, a slight decrease in the transmittance value for specific bands in infrared spectra showed a slight effect of CC-TAPT-COF on the PVCL conformation. Further, results from electron microscopy and atomic force microscopy revealed a conjugate formation between PVCL and CC-TAPT-COF due to the presence of binding interactions between them. Overall, the results from several studies showed a slight effect of CC-TAPT-COF on the PVCL during conjugate formation between PVCL and CC-TAPT-COF. This study will be beneficial for the development of COF-thermoresponsive polymer conjugates with a mixture of their unique features as advanced biomaterials.

3,5-Bis(trifluoromethyl)benzyl modified triazine-based covalent organic frameworks suppressing the shuttle effect of polysulfides in lithium-sulfur batteries

We designed and synthesized BTFMB-TzDa. The conjugated triazine structure enables fast electron transfer, while the highly electronegative and large sterically hindered group can effectively inhibit the shuttle effect of polysulfides.

A simple strategy for the construction of bi-supported triazine-based covalent organic frameworks as high-performance capacitive materials

A series of hybrid materials with different carbon nanotube contents TD-COF@CNTx (x = 0.05, 0.25, 0.45, and 0.65) were successfully prepared by using a one-pot method, where x represents the mass of carbon nanotubes added during the preparation process.

Pore-interface engineering improves doxorubicin loading to triazine-based covalent organic framework

Pore-surface engineering improves anticancer drug loading over surface area enhancement in COFs.

In situ interface engineering of highly nitrogen-rich triazine-based covalent organic frameworks for an ultra-stable, dendrite-free lithium-metal anode

Highly N-rich triazine-based COFs as a multiple lithiophilic SEI layer is designed via in situ interface engineering, which induces uniform Li+ flux and plating/stripping, decreases the Li+ migration barrier, and suppresses Li-dendrite growth.

Boosting the oxygen reduction activity of non-metallic catalysts via geometric and electronic engineering through nitrogen and chlorine dual-doping.

The development of heteroatom dual-doped porous carbon frameworks with uniform doping is highly desirable for achieving highly efficient oxygen reduction reaction (ORR) activity, due to their tunable chemical and electronic structures. Herein, porous covalent triazine-based frameworks (CTFs) incorporating nitrogen/chorine dual-doped porous carbon networks were fabricated by selecting 1,3-bis(4-cyanophenyl) imidazolium chloride as a building block, in a facile and controllable way via a bottom-up strategy. The resulting nitrogen/chorine dual-doped catalyst CCTF-700 exhibits excellent ORR performance with a more positive onset and half-wave potential (0.85 V vs. RHE), higher diffusion-limited current density and significantly improved stability in comparison with the benchmark commercial 20 wt% Pt/C catalyst. It is worth mentioning that CCTF-700 shows one of the best ORR performances among all the reported metal-free electrocatalysts under alkaline conditions. This work paves the way for a controllable and reliable strategy to craft highly efficient heteroatom dual-doped carbon catalysts for energy conversion.

Single-site cobalt catalyst embedded in a covalent triazine-based framework (CTF) for photocatalytic CO2 reduction

Single-site Co-embedded CTF-TPE exhibits high photocatalytic CO2 conversion to CO with a production rate of 945 μmol g−1 h−1.

Covalent triazine-based frameworks – switching selectivity in HMF photooxidation

Switching the HMF photooxidation pathway is possible by tailoring the CTF photocatalyst.

Selective anchoring of Pt NPs on covalent triazine-based frameworks via in situ derived bridging ligands for boosting photocatalytic hydrogen evolution.

The efficient and stable production of hydrogen (H2) through Pt-containing photocatalysts remains a great challenge. Herein, we develop an effective strategy to selectively and uniformly anchor Pt NPs (∼1.2 nm) on a covalent triazine-based framework photocatalyst via in situ derived bridging ligands. Compared to Pt/CTF-1, the obtained Pt/AT-CTF-1 exhibits a considerable photocatalytic H2 evolution rate of 562.9 μmol g-1 h-1 under visible light irradiation. Additionally, the strong interaction between the Pt NPs and in situ derived bridging ligands provides remarkable stability to Pt/AT-CTF-1. Experimental investigations and photo/chemical characterization reveal the synergy of the in situ derived bridging ligands in Pt/AT-CTF-1, which can selectively anchor the Pt NPs with homogeneous sizes and efficiently improve the transmission of charge carriers. This work provides a new perspective toward stabilizing ultrasmall nanoclusters and facilitating electron transfer in photocatalytic H2 evolution materials.

A pyrrolo[3,2-b]pyrrole core containing a covalent triazine-based framework (CTF) for photocatalytic H2 production

We report herein a novel pyrrolo[3,2-b]pyrrole core containing CTF and its Pd NP or Pt NP incorporation for efficient H2 production under visible light irradiation.

In Situ Anchoring of Small-Sized Silver Nanoparticles on Porphyrinic Triazine-Based Frameworks for the Conversion of CO2 into α-Alkylidene Cyclic Carbonates with Outstanding Catalytic Activities under Ambient Conditions.

The preparation of catalytic hybrid materials by introducing highly dispersed metallic nanoparticles into porous organic polymers (POPs) may be an ideal and promising strategy for integrated CO2 capture and conversion. In terms of the carboxylative cyclization of propargyl alcohols with CO2, the anchoring of silver nanoparticles (AgNPs) on functional POPs to fabricate efficient heterogeneous catalysts is considered to be quite intriguing but remains challenging. In the contribution, well-dispersed AgNPs were successfully anchored onto the porphyrinic triazine-based frameworks by a simple "liquid impregnation and in situ reduction" strategy. The presence of N-rich dual active sites, porphyrin and triazine, which acted as the electron donor and acceptor, respectively, offered a huge opportunity for the nucleation and growth of metal nanoparticles. Significantly, the as-prepared catalyst Ag/TPP-CTF shows excellent catalytic activity (up to 99%) toward the carboxylative cyclization of propargyl alcohols with CO2 at room temperature, achieving record-breaking activities (TOF up to 615 h-1 at 1 bar and 3077 h-1 at 10 bar). Moreover, the catalyst can be easily recovered and reused at least 10 times with retention of high catalytic activity. The possible mechanism involves small-sized AgNP-mediated alkyne activation, which may promote highly efficient and green conversion of CO2. This work paves the way for immobilizing metal nanoparticles onto functional POPs by surface structure changes for enhanced CO2 catalysis.

Understanding the Poly (Triazine Imide) Crystals Formation Process: The Conversion from Heptazine to Triazine.

Poly (triazine imide) (PTI) generally obtained via ionothermal synthesis features extended π-conjugation and enhanced crystallinity. However, in-depth investigation of the polycondensation process for PTI is an onerous task due to multiple influencing factors and limited characterization techniques. Herein, to simplify the polymerization route and exclude non-essential factors, PTI was prepared by calcining only melamine and LiCl. This study aims to identify the pivotal role of LiCl in PTI formation, which can convert heptazine-based intermediates into more stable triazine-based PTI framework. Based on this discovery, we demonstrate the transformation process of the prepared samples from amorphous Bulk g-C3 N4 to regular PTI, and further prove that the reaction with LiCl causes disruption of heptazine covalent organic frameworks. Additionally, the PTI exhibits higher photocatalytic water splitting performance due to efficient charge carrier mobility and separation, as well as faster reaction kinetics. This discovery deepens understanding of the polycondensation process of PTI crystals and provides insights toward the rational design of crystalline carbon nitride-based semiconductors.

Single-layer crystalline triazine-based organic framework photocatalysts with different linking groups for H2O2 production

Harnessing solar energy for photocatalytic hydrogen peroxide (H2O2) synthesis represents a pinnacle of environmentally-sensitive and sustainable methodologies. While single-layer crystalline triazine-based organic frameworks (CTFs) are known for their prodigious photocatalytic potential in H2O2 generation, ramifications of the connecting group within the triazine ring (TR) on underlying photocatalytic mechanism warrant deeper exploration. In this study, we simulate three distinct CTFs characterized by different TR linkers: CTF-1 (benzene group (BG)), CTF-2 (horizontally-oriented naphthyl group (NGH)), and CTF-DCN (vertically-oriented naphthyl group (NGV)). These diverse TR linkers profoundly modulate the absorption band edge of CTFs, subsequently dictating the orientation and constitution of the frontier orbitals. Such modulation plays a decisive role in determining the requisite energy for photoexcitation in CTFs, orchestrating the generation and distribution of photo-induced electrons and holes. Remarkably, the NGV linkage imparts CTF-DCN with unparalleled light absorption, superior charge separation efficiency, and the lowest energy barrier for associated reactions. Through this investigation, we illuminate the pivotal influence of TR linkers in sculpting the photocatalytic dynamics of CTFs, providing fresh perspectives for architecting CTFs with amplified photocatalytic prowess in H2O2 synthesis.

All-in-one strategy to construct bifunctional covalent triazine-based frameworks for simultaneous extraction of per- and polyfluoroalkyl substances and polychlorinated naphthalenes in foods

Per- and polyfluoroalkyl substances (PFASs) and polychlorinated naphthalenes (PCNs) are of growing concern due to their toxic effects on the environment and human health. There is an urgent need for strategies to monitor and analyze the coexistence of PFASs and PCNs, especially in food samples at trace levels, to ensure food safety. Herein, a novel β-cyclodextrin (β-CD) derived fluoro-functionalized covalent triazine-based frameworks named CD-F-CTF was firstly synthesized. This innovative framework effectively combines the porous nature of the covalent organic framework and the host-guest recognition property of β-CD enabling the simultaneous extraction of PFASs and PCNs. Under the optimal conditions, a simple and rapid method was developed to analyze PFASs and PCNs by solid-phase extraction (SPE) based simultaneous extraction and stepwise elution (SESE) strategy for the first time. When coupled with liquid chromatography−tandem mass spectrometry (HPLC−MS/MS) and gas chromatography−tandem mass spectrometry (GC−MS/MS), this method achieved impressive detection limits for PFASs (0.020 −0.023 ng/g) and PCNs (0.016 −0.075 ng/g). Furthermore, the excellent performance was validated in food samples with recoveries of 76.7–107 % (for PFASs) and 78.0–108 % (for PCNs). This work not only provides a simple and rapid technique for simultaneous monitoring of PFASs and PCNs in food and environmental samples, but also introduces a new idea for the designing novel adsorbents with multiple recognition sites.

(3,3)-Connected Triazine-Based Covalent Organic Frameworks for Efficient CO2 Separation over N2 and Dye Adsorption.

Covalent organic frameworks (COFs) are a promising class of adsorption and separation materials that can meet the needs of ecological sustainability, such as the removal of carbon dioxide and organic dyes. The two synthesized (3,3)-connected triazine-based COFs demonstrate high specific surface area and good thermal and chemical stability. COFZ1 shows good CO2 adsorption selectivities for different CO2 and N2 volume percentage systems at 273 K and 1 bar, with an ideal adsorbed solution theory (IAST) CO2 selectivity (i.e., separation factor) of 35.09 for the simulated flue gas component and a CO2 adsorption capacity of 24.21 cm3 g-1. In the aqueous dye solutions, both COFs present good adsorption performance for the selected dyes, and the maximum adsorption capacities of COFZ1 for methylene blue (MB) and gentian violet (GV) reach 510 and 564 mg g-1, respectively. Each of the two COFs shows a high anti-interference performance and excellent recyclability. The adsorption capacities of two COFs for RhB (Rhodamine B), MB, and GV hardly vary with pH values and salt concentrations. The adsorption behaviors of the two COFs for dyes follow Langmuir isothermal adsorption and quasi-secondary kinetic adsorption, approaching monolayer adsorption and chemisorption.

Chemical applicability and computation of K-Banhatti indices for benzenoid hydrocarbons and triazine-based covalent organic frameworks

The novel applications in chemistry include the mathematical models of molecular structure of the compounds which has numerous findings in this area that refers to mathematical chemistry. Topological descriptors play a major role in QSAR/QSPR studies that analyses the biological and physicochemical properties of the compounds. In the recent times, a new type of topological descriptors are proposed, called K-Banhatti indices. In this study the chemical applicability of K-Banhatti indices are examined for benzenoid hydrocarbons (derivatives of benzene). These indices have shown remarkable results through the study of statistical analysis. Subsequently, triazine-based covalent organic frameworks (CoF’s) are studied for which B_1(G), B_2(G), HB_1(G), HB_2(G), {}^mB_1(G), {}^mB_2(G), and HB(G) of a graph G are computed.

Synthesizing Interpenetrated Triazine-based Covalent Organic Frameworks from CO2.

Crystalline triazine-based covalent organic frameworks (COFs) are aromatic nitrogen-rich porous materials. COFs typically show high thermal/chemical stability, and are promising for energy applications, but often require harsh synthesis conditions and suffer from low crystallinity. In this work, we propose an environmentally friendly route for the synthesis of crystalline COFs from CO2 molecules as a precursor. The mass ratio of CO2 conversion into COFs formula unit reaches 46.3 %. The synthesis consists of two steps; preparation of 1,4-piperazinedicarboxaldehyde from CO2 and piperazine, and condensation of the dicarboxaldehyde and melamine to construct the framework. The CO2 -derived COF has a 3-fold interpenetrated structure of 2D layers determined by powder X-ray diffraction, high-resolution transmission electron microscopy, and select-area electron diffraction. The structure shows a high Brunauer-Emmett-Teller surface area of 945 m2 g-1 and high stability against strong acid (6 M HCl), base (6 M NaOH), and boiling water over 24 hours. Post-modification of the framework with oxone has been demonstrated to modulate hydrophilicity, and it exhibits proton conductivity of 2.5×10-2 S cm-1 at 85 °C, 95 % of relative humidity.