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Mesoporous silica particles (MSPs) can be used as food additives, clinically for therapeutic applications, or as oral delivery vehicles. It has also been discussed to be used for a number of novel applications including treatment for diabetes and obesity. However, a major question for their possible usage has been if these particles persist structurally and retain their effect when passing through the gastrointestinal tract (GIT). A substantial breaking down of the particles could reduce function and be clinically problematic for safety issues. Hence, we investigated the biostability of MSPs of the SBA-15 kind prepared at large scales (100 and 1000 L). The MSPs were orally administered in a murine model and clinically in humans. A joint extraction and calcination method was developed to recover the MSPs from fecal mass, and the MSPs were characterized physically, structurally, morphologically, and functionally before and after GIT passage. Analyses with N2 adsorption, X-ray diffraction, electron microscopy, and as a proxy for general function, adsorption of the enzyme α-amylase, were conducted. The adsorption capacity of α-amylase on extracted MSPs was not reduced as compared to the pristine and control MSPs, and adsorption of up to 17% (w/w) was measured. It was demonstrated that the particles did not break down to any substantial degree and retained their function after passing through the GITs of the murine model and in humans. The fact the particles were not absorbed into the body was ascribed to that they were micron-sized and ingested as agglomerates and too big to pass the intestinal barrier. The results strongly suggest that orally ingested MSPs can be used for a number of clinical applications. Validerad;2023;Nivå 2;2023-03-08 (joosat);Licens fulltext: CC BY License

Despite the growing use of organic or mixed solvents in zeolite processing, most studies focus only on aqueous suspension systems. We investigated the colloidal characteristics of submicron-sized zeolite NaA in mixed ethanol-water solvents. The effects of the mixing ratio of solvents and various additives on the dispersion of the zeolite powders were studied. The zeolite NaA particles were destabilized in solvent mixtures at a high ethanol-to-water ratio, a reduction in the zeta potential was observed, and the destabilization was rationalized by the Derjaguin, Landau, Verwey, Overbeek (DLVO) theory. An improved stabilization of the zeolite NaA suspensions was achieved in ethanol-rich solvent mixtures using nonionic low molecular weight organic additives, but not with their ionic counterparts such as anionic, cationic surfactants or inorganic acids or bases. Polyethylene glycol (PEG)-400 was found to be a good dispersant for the submicron-sized zeolite NaA particles in the ethanol-water mixtures, which was attributed to its interaction with the zeolite surface, leading to an increased zeta potential. The PEG-stabilized zeolite suspensions led to low suspension viscosities as well as uniform and consistent spin-coated films.

Although it is established that the force-induced electric polarization field of piezoelectric semiconductors can be used to tune the transfer rate of photoexcited charge carriers, there is still a lack of successful strategies to effectively improve the photocatalytic reactivity and solar-to-chemical conversion efficiency (SCC) of piezoelectric materials. Here, we are the first to prepare and study a kind of catalyst based on nanopiezoelectric heterostructures of LiNbO3-type ZnTiO3·TiO2 and tetragonal BaTiO3 with Pt or FeOx nanoparticle modification (i.e., ZBTO-Pt or ZBTO-FeOx) for reactive species generation. With respect to the production of •OH and •O2- radicals, higher amounts were observed in piezophotocatalysis relative to those for individual piezo- and photocatalysis. Benefiting from the charge transfer resistance decreases by the deposition of Pt and FeOx, the amounts of •OH radicals formed on ZBTO-Pt and ZBTO-FeOx were approximately 48 and 21% higher than that on isolated ZBTO during piezophotocatalysis, and for the amounts of •O2- radicals the enhancements were approximately 11 and 6%, respectively. Furthermore, the concentrations of H2O2 formed on ZBTO-Pt and ZBTO-FeOx under piezophotocatalysis reached approximately 315 and 206 μM after 100 min of reaction (and was still increasing) corresponding to 0.10 and 0.06% SCCs, respectively, which were also much higher than the concentrations and SCCs observed for piezo- and photocatalysis. The enhancements of piezophotocatalytic activities with these piezoelectric materials were related to the mechanical strain exerted on ZBTO, which generated a larger electric polarization field than those on ZnTiO3·TiO2 and BaTiO3 as analyzed by a finite element method. This high-intensity electric polarization field accelerated the separation and transportation of photoexcited charge carriers in the highly sunlight responsive nanopiezoelectric heterostructures based on ZBTO-Pt and ZBTO-FeOx.

A femtosecond laser process is presented increasing the surface area of copper electrocatalysts for an electrochemical CO2 reduction reaction (CO2RR). The laser treatment allows us to tune the surf ...

Electronic structure calculations are fundamentally important for the interpretation of nuclear magnetic resonance (NMR) spectra from paramagnetic systems that include organometallic and inorganic compounds, catalysts, or metal-binding sites in proteins. Prediction of induced paramagnetic NMR shifts requires knowledge of electron paramagnetic resonance (EPR) parameters: the electronic g tensor, zero-field splitting D tensor, and hyperfine A tensor. The isotropic part of A, called the hyperfine coupling constant (HFCC), is one of the most troublesome properties for quantum chemistry calculations. Yet, even relatively small errors in calculations of HFCC tend to propagate into large errors in the predicted NMR shifts. The poor quality of A tensors that are currently calculated by density functional theory (DFT) constitutes a bottleneck in improving the reliability of interpretation of the NMR spectra from paramagnetic systems. In this work, electron correlation effects in calculations of HFCCs with a hierarchy of ab initio methods were assessed, and the applicability of different levels of DFT approximations and the coupled cluster singles and doubles (CCSD) method was tested. These assessments were performed for the set of selected test systems comprising an organic radical, and complexes with transition metal and rare-earth ions, for which experimental data are available. Severe deficiencies of DFT were revealed but the CCSD method was able to deliver good agreement with experimental data for all systems considered, however, at substantial computational costs. We proposed a more computationally tractable alternative, where the A was computed with the coupled cluster theory exploiting locality of electron correlation. This alternative is based on the domain-based local pair natural orbital coupled cluster singles and doubles (DLPNO-CCSD) method. In this way the robustness and reliability of the coupled cluster theory were incorporated into the modern formalism for the prediction of induced paramagnetic NMR shifts, and became applicable to systems of chemical interest. This approach was verified for the bis(cyclopentadienyl)vanadium(II) complex (vanadocene), and the metal-binding site of the Zn(II) → Co(II) substituted superoxide dismutase (SOD) metalloprotein. Excellent agreement with experimental NMR shifts was achieved, which represented a substantial improvement over previous theoretical attempts. Effects of vibrational corrections to orbital shielding and hyperfine tensor were evaluated and discussed within the second-order vibrational perturbation theory (VPT2) framework.

Methane has been successfully encapsulated within cages of C60 fullerene, which is an appropriate model system to study confinement effects. Its chemistry and physics are also relevant for theoretical model descriptions. Here we provide insights into intermolecular interactions and predicted spectroscopic responses of the CH4@C60 complex and compared them with results from other methods and with data from the literature. Local energy decomposition analysis (LED) within the domain-based local pair natural orbital coupled cluster singles, doubles, and perturbative triples (DLPNO-CCSD(T)) framework was used, and an efficient protocol for studies of endohedral complexes of fullerenes is proposed. This approach allowed us to assess energies in relation to electronic and geometric preparation, electrostatics, exchange, and London dispersion for the CH4@C60 endohedral complex. The calculated stabilization energy of CH4 inside the C60 fullerene was −13.5 kcal mol−1 and its magnitude was significantly larger than the latent heat of evaporation of CH4. Evaluation of vibrational frequencies and polarizabilities of the CH4@C60 complex revealed that the infrared (IR) and Raman bands of the endohedral CH4 were essentially “silent” due to the dielectric screening effect of C60, which acted as a molecular Faraday cage. Absorption spectra in the UV-vis domain and ionization potentials of C60 and CH4@C60 were predicted. They were almost identical. The calculated 1H/13C NMR shifts and spin–spin coupling constants were in very good agreement with experimental data. In addition, reference DLPNO-CCSD(T) interaction energies for complexes with noble gases (Ng@C60; Ng = He, Ne, Ar, Kr) were calculated. The values were compared with those derived from supramolecular MP2/SCS-MP2 calculations and estimates with London-type formulas by Pyykko and coworkers [Phys. Chem. Chem. Phys., 2010, 12, 6187–6203], and with values derived from DFT-based symmetry-adapted perturbation theory (DFT-SAPT) by Hesselmann & Korona [Phys. Chem. Chem. Phys., 2011, 13, 732–743]. Selected points at the potential energy surface of the endohedral He2@C60 trimer were considered. In contrast to previous theoretical attempts with the DFT/MP2/SCS-MP2/DFT-SAPT methods, our calculations at the DLPNO-CCSD(T) level of theory predicted the He2@C60 trimer to be thermodynamically stable, which is in agreement with experimental observations.

The chemisorption of CO2 on aminated silica has a rich chemistry, and its details are important to research in relation to CO2 capture and catalytic chemistry. In this study, such chemisorption was investigated on aminated and diaminated silica with 1H and 13C solid state nuclear magnetic resonance (NMR) spectroscopy under dry and wet conditions. Fast magic-angle spinning (MAS) allowed us to obtain high resolution spectra. Porous silica was modified into a monoaminated version using (3-aminopropyl)triethoxysilane (APTS) and a diaminated one by using 3-(2-aminoethylamino)propyltriethoxysilane (AEAPTS). From the corresponding NMR spectra we could conclude that, under dry conditions, CO2 chemisorbed as carbamic acid and carbamate ammonium ion pairs and gave similar spectra for both directly-excited 13C and under cross-polarization (CP) {1H}13C MAS NMR. Under wet conditions, direct excitation and {1H}13C CPMAS NMR showed that carbamate ammonium ion pairs formed along with bicarbonates (HCO3−). For the wet conditions, the 13C and 1H NMR spectra were especially well resolved, and we could detect two different types of carbamate ammonium ion pairs forming on the diaminated silica. We conclude that carbamate ammonium ion pairs and HCO3− moieties can be detected by {1H}13C MAS NMR, at least qualitatively, in addition to the more time consuming direct excitation.

The oxygen reduction reaction (ORR) is central in carbon-neutral energy devices. While platinum group materials have shown high activities for ORR, their practical uses are hampered by concerns over deactivation, slow kinetics, exorbitant cost, and scarce nature reserve. The low cost yet high tunability of metal–organic frameworks (MOFs) provide a unique platform for tailoring their characteristic properties as new electrocatalysts. Herein, we report a new concept of design and present stable Zr-chain-based MOFs as efficient electrocatalysts for ORR. The strategy is based on using Zr-chains to promote high chemical and redox stability and, more importantly, tailor the immobilization and packing of redox active-sites at a density that is ideal to improve the reaction kinetics. The obtained new electrocatalyst, PCN-226, thereby shows high ORR activity. We further demonstrate PCN-226 as a promising electrode material for practical applications in rechargeable Zn-air batteries, with a high peak power density of 133 mW cm–2. Being one of the very few electrocatalytic MOFs for ORR, this work provides a new concept by designing chain-based structures to enrich the diversity of efficient electrocatalysts and MOFs.

Spherical mesoporous carbon (with a particle size in the range of 40–75 μm) was synthesized by nanoreplication of a hard silica template using sucrose as the carbon precursor. The mesoporous carbon...

Global concerns regarding climate change and the energy crisis have stimulated, among other things, research on renewable and sustainable materials. In relation to that, hydrothermal carbonization of wet biomass has been shown to be a low-cost method for the production of hydrochars. Such hydrochars can be refined into materials that can be used in water purification, for CO2 capture, and in the energy sector. Here, we review the use of metal ions and particles to catalyze the formation of hydrochars and related hybrid materials. First, the effects of using silver, cobalt, tellurium, copper ions, and particles on the hydrothermal carbonization of simple sugars and biomass are discussed. Second, we discuss the structural effects of iron ions and particles on the hydrochars in conjunction with their catalytic effects on the carbonization. Among the catalysts, iron ions or oxides have low cost and allow magnetic features to be introduced in carbon-containing hybrid materials, which seems to be promising for commercial applications. Mistra and the MistraTerraClean programme

Thermosetting polymeric materials have advantageous properties and are therefore used in numerous applications. In this study, it was hypothesized and ultimately shown that thermosets could be derived from comparably sustainable sub-components. A two-step procedure to produce a thermoset comprising of Kraft lignin (KL) and the cross-linker adipic acid (AdA) was developed. The cross-linking was activated by means of an acetylating agent comprising isopropenyl acetate (IPA) to form a cross-linking mixture (CLM). The cross-linking was confirmed by FTIR and solid-state NMR spectroscopy, and the esterification reactions were further studied using model compounds. When the KL lignin was mixed with the CLM, partial esterification occurred to yield a homogeneous viscous liquid that could easily be poured into a mold, as the first step in the procedure. Without any additions, the mold was heated and the material transformed into a thermoset by reaction of the two carboxylic acid-derivatives of AdA and KL in the second step.

Methane has been successfully encapsulated within cages of C

Zeolites with appropriately narrow pore apertures can kinetically enhance the selective adsorption of CO2 over N-2. Here, we showed that the exchangeable cations (e.g., Na' or K) on zeolite ZK-4 play, an important role in the CO2 selectivity. Zeolites NaK ZK-4 with Si/Al = 1.8-2.8 had very high CO2 selectivity when an intermediate number of the exchangeable cations were K+ (the rest being Na+) Zeolites NaK ZK-4 with Si/Al = 1.8 had high CO, uptake capacity and very high CO2-over-N-2 selectivity (1190). Zeolite NaK ZK-4 with Si/A1 = 2.3 and 2.8 also had enhanced CO2 selectivity with an intermediate number of K cations. The high CO, selectivity was related to the I(' cation in the 8 -rings of the alpha-cage, together with Na+ cations in the 6 -ring, obstructing the diffusion of N2 throughout the zeolite. The positions of the K+ cation in the 8 -ring moved slightly (max 0.2 angstrom) toward the center of the a-cage upon the adsorption of CO2, as revealed by in situ X-ray diffraction. The CO2-over-N-2 selectivity was somewhat reduced when the number of K+ cations approached 100%. This was possibly due to the shift in the IC' cation positions in the 8 -ring when the number of Na+ was going toward 0%, glowing N, diffusion through the 8 -ring. According to 'm situ infrared spectroscopy, the amount of chemisorbed CO2 was reduced on zeolite ZK-4s with increasing Si/Al ratio. In the context of potential applications, a kinetically enhanced selection of CO2 could be relevant for applications in carbon capture and bio- and natural gas upgrading.

Carbon dioxide must be removed from biogas or natural gas to obtain compressed or liquefied methane, and adsorption-driven isolation of CO2 could be improved by developing new adsorbents. Zeolite adsorbents can select CO2 over CH4, and the adsorption of CH4 on zeolite |Na12-xKx|-A is significantly lower for samples with a high K+ content, i.e., x > 2. Nevertheless, we show, using 1H NMR experiments, that these zeolites adsorb CH4 after long equilibration times. Pulsed-field gradient NMR experiments indicated that in large crystals of zeolites |Na12-xKx|-A, the long-time diffusion coefficients of CH4 did not vary with x, and the upper limit of the mean-square displacement was about 1.5 μm, irrespective of the diffusion time. Also for zeolite |Na12|-A samples of three different particle sizes (∼0.44, ∼2.9, and ∼10.6 μm), the upper limit of the mean-square displacement of CH4 was 1.5 μm and largely independent of the diffusion time. This similarity provided further evidence for an intracrystalline diffusion restriction for CH4 within the medium- and large-sized zeolite A crystals and possibly of clustering and close contact among the small zeolite A crystals. The upper limit of the long-time diffusion coefficient of adsorbed CH4 was (at 1 atm and 298 K) about 10-10 m2/s irrespective of the size of the zeolite particle or the studied content of K+ in zeolites |Na12-xKx|-A and |Na12|-A. The T1 relaxation time for adsorbed CH4 on zeolites |Na12-xKx|-A with x > 2 was smaller than for those with x < 2, indicating that the short-time diffusion of CH4 was hindered.

Amine-modified adsorbents are being researched for their potential to capture CO2 from various gas mixtures, and we review how IR spectroscopy has been used to study the associated CO2–amine chemistry. It has been used to reveal that CO2 chemisorbs as ammonium-carbamate ion pairs especially when the amine density is high. Carbamic acid and related other moieties tend to form in parallel to the ion pairs when the amine density is low. The amines have been shown to degrade on cyclic heat treatment. To further study the formation of bicarbonates on reactive adsorption of CO2 and H2O, degradation of the organics, and the use of other supports than silica are suggested.

Reduction of sulfur-containing compounds from fossil fuel is vital. This work reports on the adsorptive removal of benzothiophene (BT) from liquid fuel using a highly porous metal-organic framework based on a bicomponent zirconium(IV) benzene-tricarboxylate Zr(BTC), and its post-synthetically modified hybrid form with dodeca-tungstophosphoric acid (HPW/Zr(BTC). The HPW loading for the high-performing hybrid adsorbents was 0.5–2.0 wt/wt of W/Zr. Temperature and concentration dependent BT adsorption data were in good agreement with the non-linear Langmuir model combined with a van’t Hoff description of the heat of adsorption. The maximum predicted adsorption capacities were estimated to be 290 and 238 mg.g−1 for HPW(1.5)/Zr(BTC) and Zr(BTC) comparable to the contemporary reported adsorbents. The adsorption kinetics followed a pseudo-second order model, which was related to the low concentration of BT used for these studies. Although the highly porous Zr(BTC) had good adsorptive sites, its adsorption capacity was enhanced by incorporation of HPW, this was attributed to availability of added acid sites for adherence of basic BT. The adsorption findings were further corroborated with DFT calculations, which showed favorable BT adsorption with calculated binding energies of −140.2 and −47.3 kJ.mol−1 for HPW(1.5)/Zr(BTC) and Zr(BTC), respectively. Much of adsorption sites were retained after regeneration of adsorbents.

Raw biogas is a renewable fuel that can be upgraded into biomethane using several technologies that include adsorption-driven processes. We evaluated two adsorbents using a lab-sized pressure-vacuum-swing adsorption (PVSA) unit. Pellets of nano-sized zeolite A (|Na12|-A and |Na10K2|-A) were prepared together with a clay-based binder and sintered for 1–3 h at 450–650°C. The pellets were subsequently PVSA tested to record the steady-state conditions and breakthrough of CO2. Numerous cycles were recorded with pellets that had been activated at 200°C under dynamic vacuum. The working capacity for CO2 removal exceeded 1.2 mol/kg at a raw-biogas pressure of 4 bar, and the nano-|Na10K2|-A adsorbent had a low CH4 slip.

Methane has been successfully encapsulated within cages of C60 fullerene, and it is an appropriate model system to study confinement effects. Its chemistry and physics is also relevant for theoretical model descriptions. Here we provided insights into intermolecular interactions and predicted spectroscopic responses of the CH4@C60 complex and compared with results from other methods and with literature data. Local energy decomposition analysis (LED) within the domain-based local pair natural orbital coupled cluster singles, doubles, and perturbative triples (DLPNO-CCSD(T)) framework was used, and an efficient protocol for studies of endohedral complexes of fullerenes is proposed. This approach allowed us to assess energies in relation to electronic and geometric preparation, electrostatics, exchange, and London dispersion for the CH4@C60 endohedral complex. The calculated stabilization energy of CH4 inside the C60 fullerene was −13.5 kcal/mol and its magnitude was significantly larger than the latent heat of evaporation of CH4. Evaluation of vibrational frequencies and polarizabilities of the CH4@C60 complex revealed that the infrared (IR) and Raman bands of the endohedral CH4 were essentially “silent” due to dielectric screening effect of the C60, which acted as a molecular Faraday cage. Absorption spectra in the UV-Vis domain and ionization potentials of the C60 and CH4@C60 were predicted. They were almost identical. The calculated 1H/13C NMR shifts and spin-spin coupling constants were in very good agreement with experimental data. In addition, reference DLPNO-CCSD(T) interaction energies for complexes with noble gases(Ng@C60 ; Ng = He, Ne, Ar, Kr) were calculated. The values were compared with those derived from supermolecular MP2/SCS-MP2 calculations and estimates with London-type formulas by Pyykkö and coworkers [Phys. Chem. Chem. Phys., 2010, 12, 6187-6203], and with values derived fromDFT-based symmetry-adapted perturbation theory (DFT SAPT) by Hesselmann & Korona [Phys. Chem. Chem. Phys., 2011, 13, 732-743]. Selected points at the potential energy surface of the endohedral He2@C60 trimer were considered. In contrast to previous theoretical attempts with the DFT/MP2/SCS-MP2/DFT-SAPT methods, our calculations at the DLPNO-CCSD(T) level of theory predicted the He2@C60 trimer to be thermodynamically stable, which is in agreement with experimental observations.

Metal-free nitrogen-doped carbon is considered as a green functional material, but the structural determination of the atomic positions of nitrogen remains challenging. We recently demonstrated that directly-excited solid state 15N NMR (ssNMR) spectroscopy is a powerful tool for the determination of such positions in N-doped carbon at natural 15N isotope abundance. Here we report a green chemistry approach for the synthesis of N-doped carbon using cellulose as a precursor, and a study of the catalytic properties and atomic structures of the related catalyst. N-doped carbon (NH3) was obtained by the oxidation of cellulose with HNO3 followed by ammonolysis at 800 °C. It had a N content of 6.5 wt% and a surface area of 557 m2 g-1, and 15N ssNMR spectroscopy provided evidence for graphitic nitrogen besides regular pyrrolic and pyridinic nitrogen. This structural determination allowed probing the role of graphitic nitrogen in electrocatalytic reactions, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and nitrite reduction reaction. The N-doped carbon catalyst (NH3) showed higher electrocatalytic activities in the OER and HER under alkaline conditions and higher activity for nitrite reduction, as compared with a catalyst prepared by the carbonization of HNO3-treated cellulose in N2. The electrocatalytic selectivity for nitrite reduction of the N-doped carbon catalyst (NH3) was directly related to the graphitic nitrogen functions. Complementary structural analyses by means of 13C and 1H ssNMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature N2 adsorption were performed and provided support to the findings. The results show that directly-excited 15N ssNMR spectroscopy at natural 15N abundance is generally capable of providing information on N-doped carbon materials if relaxation properties are favorable. It is expected that this approach can be applied to a wide range of solids with an intermediate concentration of N atoms.

Metal-free nitrogen-doped carbon is considered as a green functional material, but the structural determination of the atomic positions of nitrogen remains challenging. We recently demonstrated that directly-excited solid state 15N NMR (ssNMR) spectroscopy is a powerful tool for the determination of such positions in N-doped carbon at natural 15N isotope abundance. Here we report a green chemistry approach for the synthesis of N-doped carbon using cellulose as a precursor, and a study of the catalytic properties and atomic structures of the related catalyst. N-doped carbon (NH3) was obtained by the oxidation of cellulose with HNO3 followed by ammonolysis at 800 °C. It had a N content of 6.5 wt% and a surface area of 557 m2 g-1, and 15N ssNMR spectroscopy provided evidence for graphitic nitrogen besides regular pyrrolic and pyridinic nitrogen. This structural determination allowed probing the role of graphitic nitrogen in electrocatalytic reactions, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and nitrite reduction reaction. The N-doped carbon catalyst (NH3) showed higher electrocatalytic activities in the OER and HER under alkaline conditions and higher activity for nitrite reduction, as compared with a catalyst prepared by the carbonization of HNO3-treated cellulose in N2. The electrocatalytic selectivity for nitrite reduction of the N-doped carbon catalyst (NH3) was directly related to the graphitic nitrogen functions. Complementary structural analyses by means of 13C and 1H ssNMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature N2 adsorption were performed and provided support to the findings. The results show that directly-excited 15N ssNMR spectroscopy at natural 15N abundance is generally capable of providing information on N-doped carbon materials if relaxation properties are favorable. It is expected that this approach can be applied to a wide range of solids with an intermediate concentration of N atoms.

Metal-free nitrogen-doped carbon is considered as a green functional material, but the structural determination of the atomic positions of nitrogen remains challenging. We recently demonstrated that directly-excited solid state 15N NMR (ssNMR) spectroscopy is a powerful tool for the determination of such positions in an N-doped carbon at natural 15N isotope abundance. Here we present a green chemistry approach to the synthesis of N-doped carbon using cellulose as precursor, and a study of the catalytic properties and atomic structures of the related catalyst. The N-doped carbon (NH3) was obtained by oxidation of cellulose with HNO3 followed by ammonolysis at 800°C. It had a N content of 6.5 wt.% and a surface area of 557 m2 g–1, and 15N ssNMR spectroscopy provided evidence for graphitic nitrogen besides of regular pyrrolic and pyridinic nitrogen. This structure determination enabled probing the role of graphitic nitrogen for electrocatalytic reactions, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and nitrite reduction reaction. The N-doped carbon catalyst (NH3) had higher electrocatalytic activities in OER and HER under alkaline conditions and a higher activity for nitrite reduction, as compared with a catalyst prepared by carbonization of the HNO3-treated cellulose in N2. The electrocatalytic selectivity for nitrite reduction of the N-doped carbon catalyst (NH3) was directly related to the graphitic nitrogen functions. Complementary structural analysis by means of 13C and 1H ssNMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature N2 adsorption were preformed and provided support to the findings. The results show that directly-excited 15N ssNMR at natural 15N abundance is generally capable to provide information on N-doped carbon materials, and it is expected that the approach can be applied to a wide range of solids with an intermediate amount of N atoms.

Microporous organic polymers (MOPs) with internal pores less than 2 nm have potential use in gas separation, sensing, and storage, in the form of membranes, monoliths, fibers, or adsorbent granules. These covalently bonded polymers are being formed by reacting with rigid organic monomers, and MOPs have lately been studied for capturing CO2 from gas mixtures in the form of membranes and adsorbents. Especially, the potential of MOPs in the processes of carbon capture and storage has been in the focus and small pore MOPs are preferred for regular separation processes but larger pores could be suitable if cryogenic processes would be used. Recent studies (2014 – mid 2019) on the potential use of MOPs as CO2 adsorbents and, to some degree, CO2-selective membranes are reviewed.

The effect of two process water (PW) recirculation strategies after the hydrothermal carbonization (HTC) of brewers spent grains (BSG) is evaluated with the focus on the hydrochar characteristics. The HTC process has been carried out under different operating conditions; residence time between 2 - 4 h and temperature in the range of 200 - 220 °C. The hydrochars composition reveals that operating conditions have a more significant effect than PW recirculation on the hydrochar composition. The composition of the liquid produced at HTC plus PW recirculation process is essentially controlled by the operating temperature, for instance, the total organic carbon (TOC) in the PW changes in the narrow range of 200 - 220 °C. A detailed analysis of PW has also been done. The main components of the liquid phase are lactic, formic, acetic, levulinic, and propionic acid and 5-hydroxymethylfurfural, that affect the surface structure of the hydrochars.

Sulfur-containing compounds are undesirable in fossil fuels, thus stringent regulations are in place to curb their atmospheric emissions. In this context, we hypothesized and showed that acid catalysis promoted by metal particles could be used to oxidize dibenzothiophene (DBT) and benzothiophene (BT) into sulfones that, in principle, can be subsequently removed. In specific, we studied the oxidative step of catalytic oxidative desulfurization (CODS) processes using a new bifunctional catalyst based on Pd-promoted molybdovanadophosphoric acid (Pd-PMV) supported on mesoporous zirconia (Pd-PMV/mZrO2). The PMV was supported on zirconia using a one-pot sol–gel method, and the Pd nanoparticles were deposited in a subsequent step. The activity of catalyst was excellent, with high conversions >99% and a turnover frequency (TOF) value of 384 h−1 for DBT, using catalyst Pd-15PMV/mZrO2, which had 15-wt% loading of PMV. tert-butyl hydrogen peroxide (tBHP) was used as an oxidant under relatively mild reaction conditions. The catalyst had both Bronsted and Lewis acid sites, and the Pd nanoparticles enhanced its synergistic catalytic performance. Up to a threshold level loading of PMV, the thermal stability of the catalysts was higher than the underlying mZrO2 support. A high catalytic activity was maintained with only a minor loss over 10 cycles, making the catalyst promising for oxidative deep-desulfurization of liquid hydrocarbon fuels.

Highly microporous humins were synthesized from readily available sugars and bio-based polymers (monosaccharides, disaccharides, and polysaccharides) in sulfuric acid followed by a diethyl ether wa...

Zeolite |Na12|-A is a commercial adsorbent, and its CO2-over-N2(CH4) selectivity can be further enhanced kinetically by replacing Na+ in the 8-ring windows that control gas diffusion with large cations. In this study, samples of zeolite |Na12–xKx|-A with x = 0.0, 0.8, 2.0, and 3.0 were prepared, and the positions of adsorbed CO2 molecules were determined using in situ neutron powder diffraction through profile refinement. Adsorbed CO2 molecules were located at three different sites within the large α-cavities in the zeolite structure, revealing the interaction between the adsorbed CO2 and the host framework. The number of CO2 molecules at each site depends on CO2 pressure and follows site-specific CO2 isotherms described with a Langmuir model. Most of the CO2 molecules in zeolite |Na12–xKx|-A bridge two cations at neighboring 8-ring sites. These are relatively weakly physisorbed, and therefore, most of the working capacity of CO2 adsorption is related to this site. The CO2 molecules at the second most pop...

Activated carbons (ACs) have applications in gas separation and power storage, and N-doped ACs in particular can be promising supercapacitors. In this context, we studied ACs produced from yeast-de...