High-resolution Thermogravimetry Research Articles

Optimized preparation, thermal characterization and microwave absorption properties of deep eutectic solvents made by choline chloride and hydrated salts of alkali earth metals

In this manuscript, we provided insights into the preparation of Deep Eutectic Solvents (DESs) made by choline chloride and MgCl2·6H2O or CaCl2·6H2O, proposed as green solvents for the valorization of biomasses, and we performed an extensive evaluation of their thermal properties. In particular, we highlighted the use of a microwave (MW) coaxial antenna as a rapid, efficient, and eco-friendly heating probe, which can reduce the preparation time up to 40 times with respect to conventional heating without altering the final properties of the product. The thermal properties of the DESs were extensively studied by Differential Scanning Calorimetry and High-Resolution Thermogravimetry with analysis of the evolved gas by Fourier Transformed Infra-Red spectroscopy, with the aim to obtain important information on their thermal stability and thermal degradation mechanism. The experimental data also allowed us to obtain indirect evidence of the hydrogen bonding network formed in DES nanostructures. Finally, the evaluation of the samples’ capability to absorb MWs allowed us to classify them as good MW absorbers, highlighting their potential for future applications in MW-assisted processes.

Capturing spatially resolved kinetic data and coking of Ga-Pt supported catalytically active liquid metal solutions during propane dehydrogenation in situ.

Supported liquid phase catalysis has great potential to unify the advantages from both homogeneous and heterogeneous catalysis. Recently, we reported supported catalytically active liquid metal solutions (SCALMS) as a new class of liquid phase catalysts. SCALMS enable high temperature application due to the high thermal stability of liquid metals when compared to supported molten salts or ionic liquids. The highly dynamic liquid metal/gas interface of SCALMS allows for catalysis over single atoms of an active metal atom within a matrix of liquid gallium. In the present study, kinetic data is acquired along the catalyst bed in a compact profile reactor during propane dehydrogenation (PDH) over gallium-platinum SCALMS. The reactor design allows for the analysis of the temperature and gas phase composition along the catalyst bed with a high spatial resolution using a sampling capillary inside the reactor. The concentration profiles suggest enhanced deactivation of the catalyst at the end of the bed with a deactivation front moving from the end to the beginning of the catalyst bed over time on stream. Only minor amounts of side products, formed via cracking of propane, were identified, supporting previously reported high selectivity of SCALMS during alkane dehydrogenation. The acquired data is supported by in situ high-resolution thermogravimetry coupled with mass spectrometry to monitor the activity and coking behaviour of SCALMS during PDH. The results strongly suggest an enhanced formation of coke over Al2O3-supported SCALMS when compared to using SiO2 as the support material.

Co-Pyrolysis of Low-Density Polyethylene and Motor Oil—Investigation of the Chemical Interactions between the Components

In this work, different thermal analysis methods have been used to study the co-pyrolysis of low-density polyethylene (LDPE) and motor oil. Two kinds of motor oil were considered, a fresh one and a used one. Through the comparison of experimental curves and so-called “theoretical curves”, high-resolution thermogravimetry experiments allowed highlighting interactions between the LDPE and each of the two oils, when they are co-pyrolyzed. While thermogravimetry coupled with mass spectrometry did not give any insights into these interactions, pyrolysis coupled to gaseous chromatograph and mass spectrometry allowed identifying aldehydes in the products of the co-pyrolysis of LDPE and each of the two oils. These aldehydes were not observed during the pyrolysis of the LDPE or the oils alone. On the basis of these results, various explanations for the formation of these aldehydes are proposed.

Lithiated Nanoparticles Doped with Ionic Liquids as Quasi-Solid Electrolytes for Lithium Batteries

This work reports two quasi-solid composite electrolytes based on LiFT (Lithiated Fluorinated Titania) nanopowder and either 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) or 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) ionic liquid (IL). In details, LiFT nanopowder is doped with ca. 30 wt% of IL, giving rise to materials with formula LiFT/(EMImBF4)0.183 and LiFT/(EMImTFSI)0.087. The resulting composite electrolytes appear as powder-like solids as the IL is completely absorbed by LiFT. The correlation between structure, thermal properties and long-range charge migration processes of the here proposed electrolytes is investigated by several characterization techniques, as follows: i) differential scanning calorimetry (DSC) and high-resolution thermogravimetry (HR-TGA); ii) Fourier-transform infrared spectroscopy in both the medium and the far infrared (FT-MIR and FT-FIR); and iii) broadband electrical spectroscopy (BES). The conductivity of the here proposed composite electrolytes is promising. Indeed, at 30 and 100 °C it corresponds respectively to 1.75 × 10−3 S cm−1 and 1.05 × 10−2 S cm−1 for LiFT/(EMImBF4)0.183, and 1.36 × 10−2 S cm−1 and 4.42 × 10−2 S cm−1 for LiFT/(EMImTFSI)0.087. Finally, LiFT/(EMImTFSI)0.087 is used to fabricate a coin cell prototype, that is tested by galvanostatic cycling for performance and durability.

Interplay Between Hydroxyl Density and Relaxations in Poly(vinylbenzyltrimethylammonium)-b-poly(methylbutylene) Membranes for Electrochemical Applications.

Anion-exchange membranes (AEMs) consisting of poly(vinyl benzyl trimethylammonium)-b-poly(methylbutylene) of three different ion exchange capacities (IECs), 1.14, 1.64, and 2.03 mequiv g-1, are studied by High-Resolution Thermogravimetry, Modulated Differential Scanning Calorimetry, Dynamic Mechanical Analysis, and Broadband Electrical Spectroscopy in their OH- form. The thermal stability and transitions are elucidated, showing a low temperature Tg and a higher temperature transition assigned to a disorder-order transition, Tδ, which depends on the IEC of the material. The electric response is analyzed in detail, allowing the identification of three polarizations (only two of which contribute significantly to the overall conductivity, σEP and σIP,1) and two dielectric relaxation events (β1 and β2), one associated with the tolyl side groups (β1) and one with the cationic side chains (β2). The obtained results are integrated in a coherent picture and a conductivity mechanism is proposed, involving two distinct conduction pathways, σEP and σIP,1. Importantly, we observed a reordering of the ion pair dipoles which is responsible for the Tδ at temperatures higher than 20 °C, which results in a dramatic decrease of the ionic conductivity. Clustering is highly implicated in the higher IEC membrane in the hydroxyl form, which reduces the efficiency of the anionic transport.

Graphene-Supported Fe, Co, Ni Carbon Nitride Electrocatalysts for the ORR in Alkaline Environment

The development of advanced energy conversion systems characterized by a high efficiency and a low environmental impact is one of the most relevant targets of modern research [1]. As of today, important research efforts are devoted to low-temperature fuel cells (FCs) mounting an acid electrolyte, typically a proton-conducting membrane (e.g., Nafion®). To achieve a performance level compatible with current applications, these systems must adopt electrocatalysts (ECs) with a significant loading of platinum-group metals (PGMs). In conventional low-temperature FCs, most of the PGM loading is typically concentrated at the FC cathode to promote the poor kinetics of the oxygen reduction reaction (ORR), one of the major bottlenecks in FC operation. Very recently, viable OH--conducting membranes were developed [2], opening the possibility to devise efficient anion-exchange membrane fuel cells (AEMFCs). In these systems the ORR takes place in an alkaline environment; accordingly, AEMFCs can adopt “Pt-free” ORR ECs and still achieve a high performance level. In this work, new “Pt-free” ORR ECs are reported; the materials comprise a graphene support “core”, which is covered by a carbon nitride “shell” coordinating the ORR active sites [3]. The proposed materials reap the benefits offered by graphene, including: (i) a high electrical conductivity, minimizing the ohmic losses; and (ii) a low microporosity, to facilitate the mass transport of reactants and products. The carbon nitride “shell” coordinates the bimetallic active sites, which include: (i) a 3d-“active metal” (i.e., Fe, Co, Ni), which bestows most of the ORR performance; and (ii) an oxophilic “co-catalyst” (Sn), which stabilizes the “active metal”and improves the ORR kinetics with a bifunctional mechanism. The chemical composition of the ECs is determined by inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis; the thermal stability is studied by high-resolution thermogravimetry (HR-TG); the surface chemical composition is explicated by X-ray photoelectron spectroscopy (XPS); the morphology is elucidated in detail by high-resolution scanning electron microscopy (HR-SEM) and high-resolution transmission electron microscopy (HR-TEM); the porosity is inspected by nitrogen physisorption techniques; the structure is investigated by wide-angle X-ray diffraction (WAXD), electron diffraction and micro-Raman; finally, the ORR performance and mechanism are clarified by means of cyclic voltammetry with the thin-film rotating ring-disk electrode (CV-TF-RRDE) method. The results proved very promising, clearly showing the potential of this family of “Pt-free”, “core-shell” graphene-supported ECs for application at the cathode of AEMFCs. In particular, CV-TF-RRDE measurements in an alkaline environment demonstrated that the best material exhibits an ORR overpotential ca.70 mV higher with respect to a 10 wt.% Pt/C reference (see Figure).

(Invited) The Use of Broadband Electric Spectroscopy to Probe the Relaxations and Polarizations in Phase Seperated Polymer Electrolytes

There has been a recent surge in interest in the use of anion exchange membranes (AEMs) as the separator in many electrochemical conversion devices such as fuel cells, electrolyzers, redox flow cells, and for uses in electrochemical water purification processes. This is because electrocatalysis is generally more facile in alkaline conditions, and so these devices could potentially operate with non-precious metal catalysts and with catalysts capable of oxidizing or generating fuels beyond hydrogen. An AEM with high anionic conductivity would overcome many of the disadvantages of proton exchange membrane devices that need precious metal catalyst and work best with hydrogen. Improved AEMs are also required for water purification applications. Realization of AEM devices, therefore, would revolutionize electrochemical energy conversion, as inexpensive versatile devices could be made available. While much attention has been focused on generating new AEMs with stable cations and backbones, very little attention has been paid to the design of AEMs to maximize ionic conductivity and water transport. The work presented here represents the first detailed study of the thermomechanical, polarization, and dielectric phenomena related to morphology in a series of AEMs. In detail in this presentation, the micro-structure is studied by Small Angle X-ray Scattering (SAXS), the thermal stability and transitions are detected by High-Resolution Thermogravimetry (HR-TG) and by Modulated Differential Scanning Calorimetry (MDSC), respectively. The mechanical properties and transitions are investigated by Dynamic Mechanical Analysis (DMA). Broadband Electrical Spectroscopy (BES) is used to study the electric response and the conductivity mechanisms of the membranes in the frequency and temperature range of 0. 01—107 Hz and -105 — 100 °C, respectively. BES is a powerful technique, which allows us to fully understand the overall electric response and dielectric relaxations of the membranes, both in a completely dry state and after full hydration, thus allowing clarification of the role played by both ion solvation phenomena and water cluster structure on performance of these materials. The integration of the information acquired by the above techniques allows us to propose a reasonable mechanism for the long-range charge migration processes in polyvinylbenzyltrimethylamne bromide-block-polymethylbutylene [PVBTMA][Br]-b-PMB, it hydoxide analogue and the random polymers of the same chemistry crosslinked by UV and thermal methods. We have also extended this study to polyphenylene-b-[PVBTMA][OH] and the pentablock quaternary ammonium functioalized analogue of the sulfonated polymer, Nexar. In amny of these polymers we observe an order-disorder transition, Tδ, where dispersed cations aglomorate due to the interactions of their dipoles. As Tδ often occurs above 0°C this phenomenom is of nterset to the development of practical devices. This study has important consequences for the design of next generation revolutionary AEMs.

Effect of Si addition on mechanical properties and high temperature oxidation resistance of Ti–B–Si hard coatings

In this work the effect of Si addition on the mechanical properties and the high temperature oxidation resistance of TiB2 coatings is investigated. Nanocrystalline Ti–B–Si coatings were prepared by magnetron sputtering using co-deposition from TiB2 and Si targets. Si addition causes decrease of hardness and effective Young's elastic modulus of the coating. Annealing in high vacuum increases the content of crystalline TiB2 phase that in turn leads to enhanced hardness. High resolution thermogravimetry together with x-ray diffraction (XRD), electron probe microanalysis (EPMA), x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) is used to investigate the processes associated with exposure to air at elevated temperatures. The formation of nanocrystalline Ti–Si–O oxide scale after exposure to air at 500°C is related to B2O3 release. Increased Si content suppresses the growth of crystal phase and contributes to the high temperature oxidation resistance. At 800°C the oxidized scale formed the layered structure of globular TiO2, columnar TiO2 and amorphous borosilicate.

Activity of B(OEt)3-MCM-41 catalyst in the MPV reduction of crotonaldehyde

Mesoporous silica material MCM-41 was functionalized with boron tri-ethoxide (B(OEt)3) groups by the grafting method and denoted as ‘B(OEt)3-MCM-41’. With the use of TEM, X-ray diffraction, high-resolution thermogravimetry (TGA) and N2 adsorption–desorption isotherms, it was shown that the initial hexagonal structure, the high specific surface area, and porosity are retained in the functionalized material. 29Si NMR- and 11B NMR- spectroscopies revealed that the surface of MCM-41 consists of boron alkoxide species. The Meerwein–Ponndorf–Verley (MPV) reduction of crotonaldehyde to but-2-en-1-ol was conducted in the presence of B(OEt)3-MCM-41 catalyst. MPV reduction of crotonaldehyde also showed that functionalization leads to the creation of Lewis acidic sites. A combination of mesoporous structure with Lewis acidic properties makes the MCM-41 functionalized with boron tri-ethoxide groups, useful as solid Lewis acid catalysts.

A Novel Route for the Amidation of Carbon Nanotubes and their Use as Rein-forcement in Epoxy Matrix Composites

One of the most frequent questions in the manufacture of composites with carbon nanotubes (CNT) is the interfacial interaction between the CNT and the matrix. In order to improve this interaction, multi-wall carbon nanotubes (MWCNT), after prior oxidation, were functionalized with amine groups by a novel route for CNT, using hexabromoacetone (HBA). MWCNT were characterized, before and after functionalization procedures, by elemental analysis, high resolution electron scanning microscopy (FEG) and TGA. Epoxy (DGEBA) matrix composites were manufactured with pristine, oxidized and amino-MWCNT, in concentrations of MWCNT ranging from 0.042 to 0.083 wt%. The composites were characterized by mechanical tests in flexural mode, differential scanning calorimetry (DSC) and thermogravimetry (TGA). Elemental analyses confirmed the increases in the contents of oxygen, after the oxidation procedure, and nitrogen, after amination using HBA, proving the efficiency of both methods for the functionalization of MWCNT. Flexural tests show there were no changes in moduli and maximum flexural strength for the composites with functionalized MWCNT when compared to the pure resin. The glass transition temperature (Tg) of composites with 0.1 wt% of aminated- MWCNT increased 18°C when compared with the Tg of the neat resin. Keywords: Chemical Functionalization, Epoxy Resins, Carbon Nanotubes, Amination, Composites.

Study of gypsum by PDSC

Calcium sulfate dihydrate has been widely characterized by both differential scanning calorimetry and thermogravimetry (TG). Two dehydration processes were reported to be partially overlapping. High resolution TG and water vapor self generated atmosphere pin-hole lid strategies were used to increase the resolution of both dehydration processes. In this study, isobaric experiments were carried out in a pressure differential scanning calorimetry cell. The approach consisted in combining the pin-hole lid with different pressures with nitrogen atmosphere. Resolution was improved at moderately low pressures. At higher pressures other processes were observed.

An in-depth in situ IR study of the thermal decomposition of yttrium trifluoroacetate hydrate

The pyrolysis of Y(CF3COO)3·nH2O at temperatures up to 1,000 °C, under flowing pure Ar, O2 and O2 saturated with water vapour, was extensively analysed. The formation of HF is observed directly and the existence of a :CF2 diradical is inferred during a trifluoroacetic acid salt decomposition. High resolution thermogravimetry, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy indicated that the exothermic one-stage decomposition of the anhydrate salt occurs at 267 °C, forming YF3. Fourier transform infrared spectroscopy identified (CF3CO)2O, CF3COF, COF2, CO2 and CO as the principal volatile species; and revealed the influence of water on the reactions liberating gaseous CF3COOH, CHF3, HF, and SiF4 (from reactions with glass or quartz components). NO2 and N2O evolution suggested that traces of CH3NO2 were present in the starting material. Thermogravimetry and X-ray diffractometry indicated that the slow hydrolysis of the fluoride occurs between 630 and 655 °C, forming a mixture of Y2O3, YOF, Y7O6F9, and YF3. The decomposition and hydrolysis temperatures are significantly lower than previously reported, which has implications for sol–gel processing.

Interplay between structural and electrochemical properties of Pt-Rh carbon nitride electrocatalysts for the oxygen reduction reaction

This report describes a new family of bimetal carbon nitride (CN) electrocatalysts for the oxygen reduction reaction (ORR) for application in polymer electrolyte membrane fuel cells (PEMFCs). The materials, which bear active sites based on Pt and Rh, are prepared with a three-step protocol consisting of: (1) the synthesis of a homogeneous zeolitic inorganic–organic polymer electrolyte (Z-IOPE) precursor; (2) the pyrolysis of the precursor at a temperature T f = 400, 500, 600, 700 or 900 °C; (3) the activation, yielding the final product. It is found that T f has a major effect on the structure and the electrochemical properties of these electrocatalysts, as determined from a wide array of independent characterization techniques including: high-resolution thermogravimetry (HR-TGA); Fourier-transform medium infrared (FT-MIR), Fourier-transform far infrared (FT-FIR) and confocal micro-Raman spectroscopies; powder X-ray diffraction (powder XRD); X-ray photoelectron spectroscopy (XPS); and electrochemical investigations carried out with the cyclic voltammetry thin-film rotating disk electrode (CV-TF-RDE) method. All the information is integrated to propose a comprehensive model correlating the effect of T f on the structure of the materials with the corresponding electrochemical performance. The best results in the ORR are obtained with materials prepared at 600 ≤ T f ≤ 700 °C. These systems present the optimal compromise between the size of the metal-rich nanoparticles, the degree of graphitization of the carbon nitride support and the concentration of ligands blocking the active sites. The best Pt-Rh electrocatalysts exhibit an ORR activity very similar to the Pt/C reference. In addition, the peculiar structure of the proposed materials, which are characterized by active sites supported on the carbon nitride bulky materials, results in a better tolerance toward typical contaminants in the ORR process such as chloride anions with respect to the Pt/C reference.

An in-depth in situ IR study of the thermal decomposition of barium trifluoroacetate hydrate

The pyrolysis of Ba(CF 3COO) 2· nH 2O at temperatures up to 1000 °C, under flowing pure Ar, O 2 and O 2 saturated with water vapour, was extensively analysed. The existence of a :CF 2 diradical is inferred and the formation of HF is observed directly for the first time during a trifluoroacetic acid salt decomposition. High resolution thermogravimetry, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy indicated that the exothermic two-stage decomposition of the anhydrate salt occurs between 282 and 325 °C, forming BaF 2 via an unstable CF 3COOBaF intermediate. Fourier transform infrared spectroscopy revealed the influence of water on the reactions of the liberated gaseous products, identifying CF 3COOH, HF, CHF 3 and CO 2 as the principal volatile species, with C 2F 4, C 2F 6, CO and SiF 4 also detected. The decomposition temperature is significantly lower than previously reported, which has implications for sol–gel processing.

Thermal stability of magnetron sputtered Si–B–C–N materials at temperatures up to 1700 °C

Thermal stability of deposited Si–B–C–N materials (film fragments or powders without a substrate) in inert gases (He and Ar) up to 1700 °C was investigated using differential scanning calorimetry, high-resolution thermogravimetry and X-ray diffraction measurements. Amorphous Si–B–C–N films were fabricated by dc magnetron co-sputtering of a single B 4C–Si target in two nitrogen–argon gas mixtures (50% N 2 + 50% Ar or 25% N 2 + 75% Ar). It was found that the deposited Si–B–C–N materials can be more stable at high temperatures in the inert atmosphere than the usually used substrates (e.g. SiC or BN). The materials with the compositions (in at.%) Si 32–33B 10C 2N 50–51, for which N/(Si + B + C) = 1.1–1.2, retained their amorphous structure up to 1600 °C without any structural transformations and detectable mass changes.

Purity evaluation and influence of carbon nanotube on carbon nanotube/graphite thermal stability

High resolution thermogravimetry has been used to evaluate the carbonaceous content in a commercial sample of single-walled carbon nanotube (SWNT). The content of SWNTs in the sample was found to be at least 77 mass% which was supported by images obtained with scanning and transmission electron microscopies (SEM and TEM). Furthermore, the influence of SWNT addition on the thermal stability of graphite in mixtures of SWNT/graphite at different proportions was investigated. The graphite stability decreased with the increased of SWNT content in the overall range of composition. This behavior could be due to the close contact between these carbonaceous species as determined by SEM analysis.

Characterization of commercial double-walled carbon nanotube material: composition, structure, and heat capacity

A purified commercial double-walled carbon nanotube (DWCNT) sample was investigated by transmission electron microscopy (TEM), thermogravimetry (TG), and Raman spectroscopy. Moreover, the heat capacity of the DWCNT sample was determined by temperature-modulated differential scanning calorimetry in the range of temperature between -50 and 290 °C. The main thermo-oxidation characterized by TG occurred at 474 °C with the loss of 90 wt% of the sample. Thermo-oxidation of the sample was also investigated by high-resolution TG, which indicated that a fraction rich in carbon nanotube represents more than 80 wt% of the material. Other carbonaceous fractions rich in amorphous coating and graphitic particles were identified by the deconvolution procedure applied to the derivative of TG curve. Complementary structural data were provided by TEM and Raman studies. The information obtained allows the optimization of composites based on this nanomaterial with reliable characteristics.

Synthesis and Properties of Ordered Mesoporous Organosilicas with Vinyl and Mercaptopropyl Surface Groups: The Effect of Ligand Concentration on Pore Structure

Ordered mesoporous organosilicas (OMOs) with vinyl and mercaptopropyl groups have been synthesized by co-condensation of tetraethyl orthosilicate (TEOS) and either triethoxyvinylsilane (TEVS) or 3-mercaptopropyltrimethoxysilane (MPTMS) with addition of sodium chloride under low acidic concetrations in the presence of poly(ethylene oxide)-block-poly(butylene oxide)-block-poly(ethylene oxide) (EO39BO47EO39) triblock copolymer template B50-6600 as a structure-directing agent. The materials have been characterized by variety of techniques including argon adsorption, small-angle X-ray scattering (SAXS), high-resolution thermogravimetry analysis (TGA), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and elemental analysis. The effect of vinyl and mercaptopropyl surface groups on the pore structure of OMOs was fully studied. Direct evidence of incorporation of vinyl and mercaptopropyl groups was provided by the FTIR and elemental analysis. The OMO samples with 15% of viny...

Cage-like mesoporous organosilicas with isocyanurate bridging groups synthesized by soft templating with poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) block copolymer

Ordered large-pore organosilicas with isocyanurate bridging groups were synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and tris[3-(trimethoxysilyl)propyl]isocyanurate (ICS) in the presence of poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) (EO 39BO 47EO 39) B50-6600 template under acidic conditions. It was shown that the extraction of the B60-5500 triblock copolymer with acidified ethanol solution was insufficient to remove completely the template; however, calcination of as-synthesized and extracted samples under air atmosphere at 200 °C, 250 °C and 300 °C caused not only the removal of the polymer but also a substantial decomposition of the ICS groups. In contrast, the heat treatment of extracted organosilicas at 360 °C in flowing nitrogen was able to fully remove the residual template without degradation of the ICS bridging groups. Characterization of the resulting materials by small angle X-ray scattering (SAXS) and X-ray powder diffraction (XRD) revealed that isocyanurate-containing organosilicas have a body-centered cubic symmetry ( Im3m). Argon adsorption–desorption isotherms of these organosilicas revealed cage-like mesopores, high surface areas and large pore volumes. The diameters of spherical cages were found to be very uniform in the range of 12–14 nm. A complete removal of triblock copolymer was confirmed by high-resolution thermogravimetry (TG), Fourier transform infrared spectroscopy (FT-IR) and CHNS elemental analysis (EA). The latter showed that the isocyanurate rings are intact in the framework and their loading is up to 1 mmol g −1. Moreover, these organosilicas were also synthesized using low acid concentration, double amount of polymer and sodium chloride; in this case the template was completely extracted and there was no need for additional heat treatment.

Cage-like ordered mesoporous organosilicas with isocyanurate bridging groups: Synthesis, template removal and structural properties

The removal of triblock copolymer template from SBA-16 cage-like ordered mesoporous organosilicas (OMOs) functionalized with bulky isocyanurate (ICS) heterocyclic bridging groups is examined. These isocyanurate-containing OMOs (ICS–OMOs) were prepared by co-condensation synthesis of tris[3-(trimethoxysilyl)propyl]isocyanurate and tetraethyl orthosilicate in the presence of poly(ethylene oxide)- block-poly(propylene oxide)- block-poly(ethylene oxide) (EO 106PO 70EO 106) triblock copolymer F127 used as a template and sodium chloride additive under low acidic conditions. Initial studies revealed that the extracted ICS–OMOs materials have a cubic structure ( Im3m symmetry), high contents of isocyanurate bridging groups (0.76 and 1.08 mmol/g) as well as pore diameters ranging from 6.6 to 7.2 nm. The effect of the heating temperature on the structural ordering, specific surface area, pore volume and cage pore diameter of the as-synthesized and extracted ICS–OMOs was investigated. In addition, the synthesis, characterization and template removal of a bifunctional cage-like periodic mesoporous organosilica (PMO) containing ethane (E) and isocyanurate bridging groups is discussed. The E–ICS–PMO samples were fabricated via one-pot synthesis using 1,2-bis(triethoxysilyl)ethane, tris[3-(trimethoxysilyl)propyl]isocyanurate and F127 block copolymer. The resulting ICS–OMOs and E–ICS–PMOs were characterized by nitrogen adsorption–desorption isotherms at −196 °C, small-angle X-ray scattering (SAXS) or low-angle powder X-ray diffraction (XRD), high-resolution thermogravimetry (TG), Fourier-transform infrared spectroscopy (FT-IR) and CHNS elemental analysis. The SAXS/XRD and nitrogen adsorption show that the use of a short extraction and temperature-controlled heating at 315 °C in flowing nitrogen is an effective way to remove the remaining polymeric template from cubic mesostructures without decomposition of isocyanurate bridging groups, as evidenced by FT-IR, TGA and CHNS analysis. Moreover, a complete thermal degradation of isocyanurate groups at 550 °C in air has led to a significant shrinkage of the mesostructure, however its ordered nature was retained.