Enhanced CO2 capture in nitrogen-enriched microporous carbons derived from Polybenzoxazines containing azobenzene and carboxylic acid units

Development of the Pipette-Tip Micro-Solid-Phase Extraction for Extraction of Rutin From Moringa oleifera Lam. Using Activated Hollow Carbon Nanospheres as Sorbents

Herein, a micro-solid-phase extraction (μSPE) method was developed using a pipette tip for rutin extraction, employing activated hollow carbon nanospheres (HCNSs) as the sorbent. Characterization of the activated carbon nanospheres through TGA, FTIR, and SEM analysis confirmed the success of the activation process. The study demonstrated the efficacy of PT-μSPE in rutin extraction under pH 2 conditions with a standard concentration of 2 mg·L-1. The optimal mass of HCNSs was found to be 2 mg, and a loading volume of 500 μL resulted in the maximum recovery of rutin. Propan-2-ol was the best elution solvent with 15 aspirating/dispensing cycles. The correlation of determination (R 2) for the calibration curve was found to be 0.9991, and the LOD and LOQ values were 0.604 and 1.830 mg·L-1, respectively. The applicability of the method was demonstrated by extracting rutin from a complex Moringa oleifera leaf extract with the relative standard deviation (RSD) of 3.26%, thereby validating this method as feasible for the extraction of useful bioactive compounds from complex plant samples.

Cellulose-Amine Porous Materials: The Effect of Activation Method on Structure, Textural Properties, CO2 Capture, and Recyclability

CO2 capture via physical adsorption on activated porous carbons represents a promising solution towards effective carbon emission mitigation. Additionally, production costs can be further decreased by utilising biomass as the main precursor and applying energy-efficient activation. In this work, we developed novel cellulose-based activated carbons modified with amines (diethylenetriamine (DETA), 1,2-bis(3-aminopropylamino)ethane (BAPE), and melamine (MELA)) with different numbers of nitrogen atoms as in situ N-doping precursors. We investigated the effect of hydrothermal and thermal activation on the development of their physicochemical properties, which significantly influence the resulting CO2 adsorption capacity. This process entailed an initial hydrothermal activation of biomass precursor and amines at 240 °C, resulting in C+DETA, C+BAPE and C+MELA materials. Thermal samples (C+DETA (P), C+BAPE (P), and C+MELA (P)) were synthesised from hydrothermal materials by subsequent KOH chemical activation and pyrolysis in an inert argon atmosphere. Their chemical and structural properties were characterised using elemental analysis (CHN), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The calculated specific surface areas (SBET) for thermal products showed higher values (998 m2 g-1 for C+DETA (P), 1076 m2 g-1 for C+BAPE (P), and 1348 m2 g-1 for C+MELA (P)) compared to the hydrothermal products (769 m2 g-1 for C+DETA, 833 m2 g-1 for C+BAPE, and 1079 m2 g-1 for C+MELA). Carbon dioxide adsorption as measured by volumetric and gravimetric methods at 0 and 25 °C, respectively, showed the opposite trend, which can be attributed to the reduced content of primary adsorption sites in the form of amine groups in thermal products. N2 and CO2 adsorption measurements were carried out on hydrothermal (C) and pyrolysed cellulose (C (P)), which showed a several-fold reduction in adsorption properties compared to amine-modified materials. The recyclability of C+MELA, which showed the highest CO2 adsorption capacity (7.34 mmol g-1), was studied using argon purging and thermal regeneration over five adsorption/desorption cycles.

Ring Opening Polymerization Used for the Production of VOC Free High-Performance Ecofriendly Novel PBZ/PDA/CeO2 Nanocomposites

This study analyzed the fabrication and characterization of polybenzoxazine/polydopamine/ceria as tertiary nanocomposites. To this end, a new benzoxazine monomer (MBZ) was fabricated based on the well-known Mannich reaction of naphthalene-1-amine, 2-tert-butylbenzene-1,4-diol and formaldehyde under ultrasonic-assisted process. Polydopamine (PDA) was used as dispersing polymer nanoparticles and surface modifier for CeO2 by in-situ polymerization of dopamine with the assistance of ultrasonic waves. Then, nanocomposites (NC)s were manufactured by in-situ route under thermal conditions. The FT-IR and 1H-NMR spectra confirmed the preparation of the designed MBZ monomer. The FE-SEM and TEM results showed the morphological aspects of prepared NCs and illustrated the distribution of CeO2 NPs in the polymer matrix. The XRD patterns of NCs showed the presence of crystalline phases of nanoscale CeO2 in an amorphous matrix. The TGA results reveal that the prepared NCs are classified as thermally stable materials.

Ultrastable Covalent Triazine Organic Framework Based on Anthracene Moiety as Platform for High-Performance Carbon Dioxide Adsorption and Supercapacitors

Conductive and porous nitrogen-rich materials have great potential as supercapacitor electrode materials. The exceptional efficiency of such compounds, however, is dependent on their larger surface area and the level of nitrogen doping. To address these issues, we synthesized a porous covalent triazine framework (An-CTFs) based on 9,10-dicyanoanthracene (An-CN) units through an ionothermal reaction in the presence of different molar ratios of molten zinc chloride (ZnCl₂) at 400 and 500 °C, yielding An-CTF-10-400, An-CTF-20-400, An-CTF-10-500, and An-CTF-20-500 microporous materials. According to N₂ adsorption–desorption analyses (BET), these An-CTFs produced exceptionally high specific surface areas ranging from 406–751 m²·g⁻¹. Furthermore, An-CTF-10-500 had a capacitance of 589 F·g⁻¹, remarkable cycle stability up to 5000 cycles, up to 95% capacity retention, and strong CO₂ adsorption capacity up to 5.65 mmol·g⁻¹ at 273 K. As a result, our An-CTFs are a good alternative for both electrochemical energy storage and CO₂ uptake.

Instant pH sensor based on the functionalized cellulose for detecting strong acid leaks

Acid spills cause large-scale environmental damage and casualties. To respond to such incidents, a sensor capable of detecting acid leaks is required. Cellulose is a useful substrate material for the fast detection of acid leaks because it has high hydrophilicity and porosity. On the other hand, methods of manufacturing cellulose-based sensors are still complicated or time-consuming. Thus, in this study, a simple and rapid synthesis method for a cellulose-based pH sensor was proposed. The functionalization of α-cellulose was achieved via chloroacetyl chloride, and Congo red was covalently immobilized to the functionalized cellulose for detecting strong acids. The manufacturing process was composed of two steps as above and finished within 8 h. The developed sensor exhibited absorbance changes in the pH range of 0.2 to 3.0, and response time was shorter than 1 s. A prototype system using this sensor was manufactured and tested, and it detected acid leaks easily and quickly.

Microporous Carbon and Carbon/Metal Composite Materials Derived from Bio-Benzoxazine-Linked Precursor for CO2 Capture and Energy Storage Applications

There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO2 capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh3)4. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (Td10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m2 g-1), high CO2 adsorption (5.40 mmol g-1 at 273 K), excellent capacitance (735 F g-1), and a capacitance retention of up to 95% after 2000 galvanostatic charge-discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C.

Advanced Carbon Materials Derived from Polybenzoxazines: A Review

This comprehensive review article summarizes the key properties and applications of advanced carbonaceous materials obtained from polybenzoxazines. Identification of several thermal degradation products that arose during carbonization allowed for several different mechanisms (both competitive ones and independent ones) of carbonization, while also confirming the thermal stability of benzoxazines. Electrochemical properties of polybenzoxazine-derived carbon materials were also examined, noting particularly high pseudocapacitance and charge stability that would make benzoxazines suitable as electrodes. Carbon materials from benzoxazines are also highly versatile and can be synthesized and prepared in a number of ways including as films, foams, nanofibers, nanospheres, and aerogels/xerogels, some of which provide unique properties. One example of the special properties is that materials can be porous not only as aerogels and xerogels, but as nanofibers with highly tailorable porosity, controlled through various preparation techniques including, but not limited to, the use of surfactants and silica nanoparticles. In addition to the high and tailorable porosity, benzoxazines have several properties that make them good for numerous applications of the carbonized forms, including electrodes, batteries, gas adsorbents, catalysts, shielding materials, and intumescent coatings, among others. Extreme thermal and electrical stability also allows benzoxazines to be used in harsher conditions, such as in aerospace applications.

Designed azo-linked conjugated microporous polymers for CO2 uptake and removal applications

In recent decade, conjugated microporous polymers (CMPs) were treated as one of the superior porous materials for CO₂ uptake. Herein, we prepared two azo-linked CMPs namely: azo-carbazole (Azo-Cz) and azo-phenothiazine (Azo-Tz) from the reduction of the corresponding nitro monomers using sodium borohydride (NaBH₄). The obtained polymers were well characterized using many spectroscopic techniques. According to TGA and BET analyses, our CMPs owned good specific surface areas (reaching 315 m² g^–1), and a significant thermal stability. It is also possessed pore sizes of 0.79 and 1.18 nm, respectively, and a reasonable char yields (max. 46 %). Based on CO₂ uptake measurements, the CO₂ adsorption capacities of these CMPs were very good: up to 40 and 94 mg g^–1 at the experiment temperatures 298 and 273 K, respectively. The great CO₂ uptake is due to high surface areas that facilitate powerful interactions with CO₂ molecules.

Meso/Microporous Carbons from Conjugated Hyper-Crosslinked Polymers Based on Tetraphenylethene for High-Performance CO2 Capture and Supercapacitor

In this study, we successfully synthesized two types of meso/microporous carbon materials through the carbonization and potassium hydroxide (KOH) activation for two different kinds of hyper-crosslinked polymers of TPE-CPOP1 and TPE-CPOP2, which were synthesized by using Friedel–Crafts reaction of tetraphenylethene (TPE) monomer with or without cyanuric chloride in the presence of AlCl₃ as a catalyst. The resultant porous carbon materials exhibited the high specific area (up to 1100 m² g⁻¹), total pore volume, good thermal stability, and amorphous character based on thermogravimetric (TGA), N₂ adsoprtion/desorption, and powder X-ray diffraction (PXRD) analyses. The as-prepared TPE-CPOP1 after thermal treatment at 800 °C (TPE-CPOP1-800) displayed excellent CO₂ uptake performance (1.74 mmol g⁻¹ at 298 K and 3.19 mmol g⁻¹ at 273 K). Furthermore, this material possesses a high specific capacitance of 453 F g⁻¹ at 5 mV s⁻¹ comparable to others porous carbon materials with excellent columbic efficiencies for 10,000 cycle at 20 A g⁻¹.

Multifunctional Polyhedral Oligomeric Silsesquioxane (POSS) Based Hybrid Porous Materials for CO2 Uptake and Iodine Adsorption

In this study, two different types of hybrid porous organic polymers (POPs), polyhedral oligomeric silsesquioxane tetraphenylpyrazine (POSS-TPP) and tetraphenylethene (POSS-TPE), were successfully synthesized through the Friedel-Crafts polymerization of tetraphenylpyrazine (TPP) and tetraphenylethene (TPE), respectively, with octavinylsilsesquioxane (OVS) as node building blocks, in the presence of anhydrous FeCl₃ as a catalyst and 1,2-dichloroethane at 60 °C. Based on N₂ adsorption and thermogravimetric analyses, the resulting hybrid porous materials displayed high surface areas (270 m²/g for POSS-TPP and 741 m²/g for POSS-TPE) and outstanding thermal stabilities. Furthermore, as-prepared POSS-TPP exhibited a high carbon dioxide capacity (1.63 mmol/g at 298 K and 2.88 mmol/g at 273 K) with an excellent high adsorption capacity for iodine, reaching up to 363 mg/g, compared with the POSS-TPE (309 mg/g).

Corrosion Resistance of Mild Steel Coated with Phthalimide-Functionalized Polybenzoxazines

Herein, we synthesized two new phthalimide-functionalized benzoxazine monomers, pPP-BZ and oPP-BZ, through Mannich reactions of 2-(4-hydroxyphenyl)isoindoline-1,3-dione (pPP) and 2-(2-hydroxyphenyl)isoindoline-1,3-dione (oPP), respectively, with p-toluidine and paraformaldehyde. The structures of these two monomers were confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy. We used differential scanning calorimetry, FTIR spectroscopy, and thermogravimetric analysis to study the polymerization behavior and thermal stability of the monomers and their corresponding polybenzoxazines. Poly(pPP-BZ) and poly(oPP-BZ) were formed on mild steel (MS) through spin-coating and subsequent thermal curing polymerization. We used various corrosion testing methods to examine the effect of the curing temperature on the corrosion resistance of the coated MS samples in 3.5 wt.% aqueous solution of NaCl. Among our tested systems, the corrosion rate reached a low of 2.78 µm·Y−1 for the MS coated with poly(pPP-BZ)180 (i.e., the coating that had been cured at 180 °C); this value is much lower than that (4.8 µm·Y−1) reported for a maleimide-based benzoxazine compound (MI-Bz)/33 wt.% ACAT (amine-capped aniline trimer) blend. Thus, the incorporation of the imide functional group into the PBZ coatings is an effective strategy for affording high-performance corrosion resistance.

Multifunctional Hypercrosslinked Porous Organic Polymers Based on Tetraphenylethene and Triphenylamine Derivatives for High-Performance Dye Adsorption and Supercapacitor

We successfully prepared two different classes of hypercrosslinked porous organic polymers (HPPs)-the tetraphenylethene (TPE) and (4-(5,6-Diphenyl-1H-Benzimidazol-2-yl)-triphenylamine (DPT) HPPs-through the Friedel-Crafts polymerization of tetraphenylethene and 4-(5,6-diphenyl-1H-benzimidazol-2-yl)-triphenylamine, respectively, with 1,4-bis(chloromethyl)benzene (Ph-2Cl) in the presence of anhydrous FeCl₃ as a catalyst. Our porous materials exhibited high BET surface areas (up to 1000 m² g^-1) and good thermal stabilities. According to electrochemical and dyes adsorption applications, the as-prepared DPT-HPP exhibited a high specific capacitance of 110 F g^-1 at a current density of 0.5 A g^-1, with an excellent cycling stability of over 2000 times at 10 A g^-1. In addition, DPT-HPP showed a high adsorption capacity up to 256.40 mg g^-1 for the removal of RhB dye from water.