Hydrogen Atoms Research Articles

Visible‐Light‐Mediated Activation of Remote C(sp3)−H Bonds by Carbon‐Centered Biradical via Intramolecular 1,5‐ or 1,6‐Hydrogen Atom Transfer

AbstractIn this study, we introduce a novel intramolecular hydrogen atom transfer (HAT) reaction that efficiently yields azetidine, oxetane, and indoline derivatives through a mechanism resembling the carbon analogue of the Norrish‐Yang reaction. This process is facilitated by excited triplet‐state carbon‐centered biradicals, enabling the 1,5‐HAT reaction by suppressing the critical 1,4‐biradical intermediates from undergoing the Norrish Type II cleavage reaction, and pioneering unprecedented 1,6‐HAT reactions initiated by excited triplet‐state alkenes. We demonstrate the synthetic utility and compatibility of this method across various functional groups, validated through scope evaluation, large‐scale synthesis, and derivatization. Our findings are supported by control experiments, deuterium labeling, kinetic studies, cyclic voltammetry, Stern–Volmer experiments, and density functional theory (DFT) calculations.

Collision of Two Plasma Diffuse Jets with the Same and Different Front Polarity at an Air Pressure of 1 Torr

In air at a pressure of 1 Torr, the mode of collision of diffuse plasma jets (PDJs) consisting of ionization waves — red streamers have been studied. PDJ were formed in a quartz tube by a capacitive discharge from two identical generators with pulses of positive and negative polarity. It has been established that, with the same polarity of voltage pulses, counter-current PDJs suppress each other’s radiation. It is shown that for different polarity of voltage pulses, the intensity of the glow in the region where the PDJ meets increases significantly. Data are presented on the effect of delays between switching on generators of different polarity on the emission spectra of PDJ. It has been established that with an increase in air humidity, an atomic hydrogen line Ha appears in the emission spectrum, as well as OH and OH+ bands, the spectral energy density (W) of some of which is commensurate with the W bands of the second positive (2+) nitrogen system. The velocity of the PDJ front was measured when two generators of different polarity were turned on.

Synergistic Molecular Alignment and Dipole Polarization in Stretched Nafion/Poly(vinylidene fluoride) Blend Membranes for High Proton Conduction in PEMFCs.

The nanostructure of Nafion and poly(vinylidene fluoride) (PVDF) blend membranes is successfully aligned through a mechanical uniaxial stretching method. The phase-separated morphology of Nafion molecules distinctly forms hydrophilic proton channels with increased connectivity, resulting in enhanced proton conductivity. Additionally, the crystalline phase of PVDF molecules undergoes a successful transformation from the α- to β-phase during membrane stretching, demonstrating an alignment of fluorine and hydrogen atoms with a TTTT(trans) structure. The aligned nanostructure of the blend film, combined with the dipole polarization of the β-phase PVDF, synergistically enhances the proton conduction through the membrane for operating proton-exchange membrane fuel cells (PEMFCs). The controlled structures of the blend membranes are thoroughly investigated using atomic force microscopy and small-angle X-ray scattering. Furthermore, the improved in-plane proton conductivity facilitates increased proton conduction at the interface between the membrane and catalyst layer in the membrane-electrode assembly, ultimately enhancing the power generation of PEMFCs.

Improvements of the increase of selenium-modified rate on the structural characteristics and antioxidant properties of Lycium barbarum polysaccharides by subcritical water method

Effects of the increase of the selenium-modified rate on the structural characteristics and antioxidant abilities of the selenized polysaccharides (Se-PS) were seldom reported. In this work, LBP1-1 purified from Lycium barbarum polysaccharides (LBP) was selenized by the subcritical water (SW) versus the traditional hot water (HW) method to obtain Se-modified SW-SeLBP1-1 and HW-SeLBP1-1, respectively. The results revealed that SW-SeLBP1-1 contained 17.49 ± 0.35 mg Se/g, significantly higher than 5.68 ± 0.05 mg/g of HW-Se-LBP1-1 and the reported before. The selenization time was reduced from 7 h to 20 min. Se modifications were mainly achieved by Se substitutions of hydrogen atoms in hydroxyl groups of LBP1-1. Xylose and galactose in LBP1-1 could be easily and regularly modified by Se, the Se modifications of the other monosaccharides showed significant different between the two methods. The generated C-O-Se groups could readily make SW-SeLBP1-1 formed a more orderly network structure than that of HW-SeLBP1-1 when Se-modified rate increased 11.81 %, resulting in its antioxidant activities increasing over 17.3 % in vitro.

Circular Economy Opportunity Utilizing Fitness for Service Methodology for Aged HIC Defected Reboiler

The phenomenon of Hydrogen-Induced Cracking (HIC) is a cracking mechanism of carbon steel material as in ASME SA- 516 pressure containing equipment operating in a wet sour H2S environment. Such phenomenon is mainly driven by the diffusion of hydrogen atoms into the carbon steel due to corrosion reaction. The Structural integrity of an in-service equipment that contain a flaw or damage such as HIC could be scrutinised using Fitness For Service (FFS) assessments as quantitative engineering evaluations. The assessments are conducted using methodologies specifically prepared for pressurized equipment. These assessments provide standard procedure that can be used to determine if pressurized equipment containing flaws could continue to operate safely for certain period of time. FFS assessments are recognized and referenced by the API Codes and Standards such as API- 510, 570, & 653, and by National Board-23. Those assessments are considered suitable methodologies for evaluating the structural integrity of pressurized equipment as heat exchangers, pressure vessels, piping systems and storage tanks where inspection has revealed degradation and flaws in the equipment. The objective of this paper isto illustrate API-579 case study of HIC of fifty (50) years operating pressurized equipment, namely reboiler.

Investigating the impact of alloying elements on hydrogen diffusion in Ti-based alloys via first-principles calculations

The diffusion of hydrogen in Ti-based alloys can lead to localized degradation of mechanical properties, resulting in hydrogen embrittlement. Therefore, identifying alloying elements that impede hydrogen diffusion is a crucial approach to mitigating hydrogen embrittlement and stress corrosion in Ti-based alloys. Utilizing first-principles calculations, we investigated the effects of 33 alloying elements on hydrogen diffusion in Ti-based alloys, including diffusion barriers and coefficients. Our findings demonstrate that elements such as Al, Ga, Si, and Zn increase the hydrogen diffusion barriers and decrease the diffusion coefficients in Ti-based alloys, thereby mitigating hydrogen embrittlement. It is revealed that the difference of electronegativity of Al, Si, Au, Ag, Pd, Ir, Zn, and Cu affects the hydrogen atom trapping ability. It also sheds light on strategies to mitigate hydrogen embrittlement in Ti-based alloys. This insight highlights their significant role in hindering the movement of hydrogen atoms within the alloys.

Growth of thick amorphous carbon films on alumina for improved tribological properties

Alumina, as a pivotal ceramic material extensively utilized in contemporary applications, the surface modification and enhancement of tribological properties are crucial. In this study, reactive magnetron sputtering was employed to deposit Ti, Si co-doped hydrogen-free (TiSi/a-C), and hydrogenated amorphous carbon films (TiSi/a-C:H) with a thickness exceeding 7 μm onto the surface of alumina ceramic substrates. Utilizing the design of the film structure, the difficulty of film-substrate adhesion was resolved by controlling the deposition time to influence the growth rate of the film, thereby enabling the reliable fabrication of thick films. The adhesion of the TiSi/a-C film exhibits the highest value, with an Lc1 value of 36.7 N. The hardness of the TiSi/a-C:H reaches a maximum of 15.2 GPa, and the hardness is closely correlated with the reaction gas utilized during its depositional process. The wear rate of amorphous carbon film decreases by 34 times compared to alumina substrate. During the dissociation of CH4 at a high hydrogen-to-carbon ratio, more hydrogen atoms are involved in the chemical reaction. The introduction of hydrogen elevates the H/E and sp3/sp2 ratios within the film, thereby favoring the generation of low-friction surfaces and refining the tribological performance of alumina ceramics.

Unveiling the Behavior of Perfluoro (2-Ethoxyethane) Sulfonic Acid Potassium (PESK) in Water/Gas System: Molecular Dynamics Simulation

Molecular dynamics method (MD) was used to study the distribution of potassium perfluoro (2-ethoxyethane) sulfonic acid (PESK) in water/gas systems. When the PESK aqueous solution system reaches equilibrium, the vast majority the fluorocarbon chain is facing toward the gas phase, while the sulfonic acid radical faces toward the water, with a very small quantity of PES− is still in the bulk solution. The weak intermolecular interactions were analyzed by IGMH method, and the interaction energy between PES− and water mainly comes from the h-bonds formed by the oxygen atom in the sulfonic acid group and hydrogen atom in water molecules. K+ are mainly distributed inside the aqueous solution, and there is only van der Waals interaction between K+ and H2O molecules. According to the distribution of ESP analysis of PES−, it is mainly the sulfonic acid groups that are negatively charged.

Modeling Electrochemical Vacancy Regeneration in Single-Walled Carbon Nanotubes.

Synthesis-induced defects in single-walled carbon nanotubes (SWCNTs) enable diverse catalytic reactions, but the nature of catalytic intermediates and how active species regeneration occurs are unclear. Using a quantum mechanics/molecular mechanics (QM/MM) hybrid methodology based on density functional theory (DFT) and a classical force-field, we explore the reactivity and electrochemical regeneration of a vacancy defect in a zigzag SWCNT. Our findings indicate that hydrolysis of the defect forms a ketone group on one carbon atom and C-H bonds on two adjacent carbons. Applying an electrochemical potential of ESHE = -0.740 V triggers a proton-coupled electron transfer (PCET), converting the ketone to a hydroxyl group. Further reduction at ESHE = -1.08 V induces another PCET, expelling the hydroxyl as water and forming an active carbon with carbene character that can react with hydrogen peroxide and perchlorate. The hydrogen atoms on neighboring carbons prevent further water dissociation, maintaining the catalytic vacancy.

Combination of oxidative and reductive effects of phenolic compounds on the degradation of aniline disinfection by-products by free radicals

In this study, we selected 13 phenolic compounds containing -COOH, -CHO, -OH, and -COCH3 functional groups as model compounds for dissolved organic matter (DOM), and explored the redox reactions during the co-degradation of phenolic compounds with aniline disinfection by-products (DBPs) at the molecular level. When phenolic compounds and aniline DBPs were degraded, phenoxy radicals and aniline radicals were the most important intermediates. Phenoxy radicals can degrade aniline DBPs via hydrogen atom abstraction (HAA) reactions, and the reaction rates were related to the reduction potentials of the compounds. Compounds containing electron-withdrawing groups were more likely to oxidize aniline DBPs. Aniline DBPs were more easily degraded by phenoxy radicals when they contained electron-donating groups, and the increase in the number of chlorine atoms inhibited the reaction rates of aniline DBPs degradation by phenoxy radicals. Although phenolic compounds can reduce aniline DBPs, there was no significant correlation between the reaction rates and the reduction potentials of the compounds. Considering the redox effects of phenolic compounds on aniline DBPs, co-degradation simulations showed that phenolics inhibited the degradation efficiency of aniline DBPs. This work provided new insights into the transformation mechanisms and degradation efficiencies of DOM and aniline DBPs when they were co-degraded.

Neurotransmitter metabolites in milk ferments of Leuconostoc mesenteroides regulate temperature-sensitive heartbeats in an ex ovo model

Accumulated evidence has supported the probiotic activity of Leuconostoc mesenteroides (L. mesenteroides) which can yield beneficial metabolites via fermentation. Here, bovine milk rich in phenylalanine（PHE) was used as a source for fermentation of L. mesenteroides. The complexes of PHE with bacterial phenylalanine hydroxylase (PheH) at two temperatures were revealed via molecular dynamics simulation. Two carbon hydrogen bonds and a Pi-Alkyl T-shaped interaction were newly formed at an active site of the PheH-PHE complex. The PheH interacted with two different hydrogen atoms in an amine of PHE via conventional hydrogen bonds at 37 °C, a temperature that accelerated the milk fermentation of L. mesenteroides. Twenty-eight metabolites including various neurotransmitters in fermented milk were identified and quantified by liquid chromatography coupled to quadrupole ion trap (Q-Trap) tandem mass spectrometry. Ex ovo injection of milk ferments into the yolk sac of chicken embryos enhanced a rising temperature-induced increase in heartbeats towards the normal resting level. The neurotransmitter-rich milk ferments hold potential for using to adjust energy metabolism, referred from heart rates, during fluctuating temperature conditions.

New polymorph of N-benzoyl-morpholine-4-carbothioamide with ten crystallographically independent molecules in the asymmetric unit: Crystal structure, Hirshfeld surface analysis and Density functional theory calculations

Herein, facile synthesis, single crystal X-ray diffraction (SC-XRD) structure, Hirshfeld surface (HS) analysis and Density functional theory (DFT) calculations of N-benzoyl-morpholine-4-carbothioamide 5(a) are presented. Hence, the synthesized compound, C12H14N2O2S 5(a), crystallizes in monoclinic crystal system having space group of P 21 with a = 22.2226 (9) Å, b = 11.7520 (3) Å, c = 24.9361 (8) Å, α = 90°, β = 111.054 (4)°, γ = 90°, Z = 20 and V = 6077.6 (4) Å3. The asymmetric unit of 5(a) contains ten crystallographically independent molecules, where the morpholine and benzene rings are in respective chair and planar conformations. In the crystal structure, some of the intermolecular, N—H···O, C—H···O and C—H···S, hydrogen bonds link the molecules into a 2D-network parallel to (010), enclosing R22(10) and R22(24) ring motifs, when viewed down the b-axis direction. Furthermore, contribution of the remaining hydrogen bonds consolidates a 3D-architecture. HS analysis clarified the importance of hydrogen atom contacts with the major contributions of H…H (46.7%), H…S/S…H (21.1%), H…C/C…H (16.5%), and H…O/O…H (12.5%). Thus, hydrogen bonding and van der Waals interactions play major role in the crystal packing. Finally, optimum molecular structure of compound 5(a) was related to the experimentally determined one employing DFT at B3LYP/6–311G(d,p) level. Subsequently, the geometry of the optimized and most stable conformation turned out to be complementary with the crystal structure. The computational calculation of compound 5(a) revealed the molecule to be chemically hard in nature with high energy intrinsic reaction pathway. The associated band gap predicted compound 5(a) to be a wide band gap material. The intrinsic reaction pathway predicts hard-core behavior exhibition of the molecule.

Synthesis, crystals structures, DFT, and anticancer activities of polycyclic heterocyclic quinones

In this work, we synthesized six polycyclic heterocyclic quinones (PHQs) and one unexpected product (compound 6). We verified all of their structures by 1HNMR, 13CNMR, and HRMS and obtained four crystal structures of the seven products. At first, we compared the crystal structures with crystal structures similar to those reported in the literature and explained their differences by conjugative effect, hyperconjugative effect, and electrostatic effect. Then, we compared the crystal structure of compound 6 with the calculated structure of compound 6. The natural bond orbital analysis showed that the calculated structure formed intramolecular hydrogen bonds, whereas the crystal structure formed intermolecular hydrogen bonds but not intramolecular hydrogen bonds. The main reason for this difference was not due to the atomic charge or the interatomic distance, but rather the energy levels of the orbitals of the lone-pair electrons. In crystal structures, the intermolecular interactions contained many weak interactions, and we used the hydrogen atom substitution (HAS) method to divide the total intermolecular interactions as several independent weak interactions and to calculate their energies. The HAS method was often successful if the substituted group did not have a strong effect on the electronic structure of the entire molecule, and we found examples in the calculations of energies of weak interactions of crystal structure of compound 6 and compound 3a. An unsuccessful example of the HAS method was the substitution of C=O group with CH2 group to eliminate the O…H-N hydrogen bond interaction from the total interaction. According to the HAS method, our calculations showed that the strength order of the weak interactions was as follows: π-π stacking > hydrogen bond > n-π stacking > σ-π stacking. For the hydrogen bond, the strength order was as follows: C=O…H-N > C-Cl…H-N > C-F…H-N. For n-π stacking interaction, the strength order was as follows: Cl-π > N-π > F-π. Finally, we selected five synthesized PHQs to test anticancer activities and some of them showed better anticancer activities than the positive control drugs.

Size-dependent activity modulation of supported Ni nanocatalysts for efficient solid-state hydrogen storage in magnesium

The activity of Nickel (Ni)-based catalysts strongly depends on their particle size and dispersion; however, achieving controllable preparation of uniform particle size with high activity remains a great challenge for Ni-based catalysts to promote efficient hydrogen storage. Here, we employ a facile Carbothermal Shock (CTS) method to obtain carbon fiber-loaded Ni-based nanocatalysts (Ni@CC) with high dispersibility and size-dependent properties, which can exhibit superior catalytic effects for solid-state hydrogen storage in MgH2. It was found that the shorter the CTS duration, the smaller the size of the Ni nanoparticles, and the better the catalytic effect. Among these, the MgH2-Ni@CC with a CTS duration of 30 s showed the best hydrogen storage performance. Its activation energy for hydrogen release was significantly decreased from 158.3 kJ⋅mol−1 for milled MgH2 to 98.6 kJ⋅mol−1. More importantly, the retention rate of hydrogen absorption capacity is 95.1 % after 30 cycles, which far exceeds the 65.5 % retention rate observed in milled MgH2. These property enhancements can be attributed to the presence of nano-sized Ni and its in situ derived Mg2Ni intermediate phases, which create more channels for hydrogen atoms diffusion. Meanwhile, the close contact between nano-Ni and the Mg/MgH2 matrix can provide active catalytic sites and low-energy interfaces for facilitating hydrogen adsorption and desorption. Our study presents a promising approach to significantly improve the hydrogen storage performance of MgH2 by modulating size-dependent catalytic activity.

Electrocatalytic nitrate reduction on Fe, Fe3O4, and Fe@Fe3O4 cathodes: Elucidating structure-sensitive mechanisms of direct electron versus hydrogen atom transfer

Electrochemical nitrate reduction (NO3RR) offers a promising avenue for treating nitrate-contaminated water and recovering ammonia (NH3), yet the complexities of direct electron transfer (DET) and hydrogen atom transfer (HAT) mechanisms crucial for efficiency remain elusive. This study bridges the gap with a combined experimental and theoretical approach, elucidating the impact of catalyst structure on NO3RR pathways. We discover that catalysts favoring strong NO3− adsorption and efficient water dissociation were more inclined towards DET, enhancing denitrification. The Fe@Fe3O4/FF cathode, leveraging the synergistic interplay between metallic Fe and Fe3O4, excelled in NO3RR via DET, achieving an NH3 yield of 0.28 mmol h−1 cm−2 and a Faradaic efficiency of 95.7% for NH3 at -1.6 V (vs. SCE), with minimal nitrite accumulation at 100 mmol/L nitrate. Conversely, the Fe/FF and Fe3O4/CC cathodes showed reduced NH3 production and increased nitrite levels, attributed to the lack of Fe3O4 and metallic Fe, respectively, resulting in a dominant HAT mechanism. Moreover, Fe@Fe3O4/FF facilitated complete denitrification in real wastewater treatment by harnessing Cl− for electrochemically mediated breakpoint chlorination. This research not only deepens our understanding of NO3RR mechanisms but also paves the way for designing superior nitrate reduction catalysts.

Synthesis of Isotypic Giant Polymolybdate Cages for Efficient Photocatalytic C-C Coupling Reactions.

The construction of isotypic high-nuclearity inorganic cages with identical pristine parent structure and increasing nuclearity is highly important for molecular growth and structure-property relationship study, yet it still remains a great challenge. Here, we provide an in situ growth approach for successfully synthesizing a series of new giant hollow polymolybdate dodecahedral cages, Mo250, Mo260-I, and Mo260-E, whose structures are growth based on giant polymolybdate cage Mo240. Remarkably, they show two pathways of nuclear growth based on Mo240, that is, the growth of 10 and 20 Mo centers on the inner and outer surfaces to afford Mo250 and Mo260-I, respectively, and the growth of 10 Mo centers both on the inner and outer surfaces to give Mo260-E. To the best of our knowledge, this is the first study to display the internal and external nuclear growth of a giant hollow polyoxometalate cage. More importantly, regular variations in structure and nuclearity confer these polymolybdate cages with different optical properties, oxidative activities, and hydrogen atom transfer effect, thus allowing them to exhibit moderate to excellent photocatalytic performance in oxidative cross-coupling reactions between different unactivated alkanes and N-heteroarenes. In particular, Mo240 and Mo260-E with better comprehensive abilities can offer the desired coupling product with yield up to 92% within 1 h.

Flavonoid as a Potent Antioxidant: Quantitative Structure-Activity Relationship Analysis, Mechanism Study, and Molecular Design by Synergizing Molecular Simulation and Machine Learning.

In this work, a quantitative structure-antioxidant activity relationship of flavonoids was performed using a machine learning (ML) method. To achieve lipid-soluble, highly antioxidant flavonoids, 398 molecular structures with various substitute groups were designed based on the flavonoid skeleton. The hydrogen dissociation energies (ΔG1, ΔG2, and ΔG3) related to multiple hydrogen atom transfer processes and the solubility parameter (δ) of flavonoids were calculated using molecular simulation. The group decomposition results and the calculated antioxidant parameters constituted the ML data set. The artificial neural network and random forest models were constructed to predict and analyze the contribution of the substitute groups and positions to the antioxidant activity. The results showed the hydroxyl group at positions B4', B5', and B6' and the branched alkyl group at position C3 in the flavonoid skeleton were the optimal choice for improving antioxidant activity and compatibility with apolar organic materials. Compared to the pyrogallol group-grafted flavonoid, the designed potent flavonoid decreased ΔG1 and δ by 2.2 and 15.1%, respectively, while ΔG2 and ΔG3 kept the favorable lower values. These findings suggest that an efficient flavonoid prefers multiple ortho-phenolic hydroxyl groups and suitable sites with hydrophobic groups. The combination of molecular simulation and the ML method may offer a new research approach for the molecular design of novel antioxidants.

Site heterogeneity and broad surface-binding isotherms in modern catalysis: Building intuition beyond the Sabatier principle

Learning the science of heterogeneous catalysis and electrocatalysis always starts with the simple case of a flat, uniform surface with an ideal adsorbate. It has of course been recognized for a century that real catalysts are more complicated. For the increasingly complex catalysts of the 21st century, this Perspective argues that surface heterogeneity and non-ideal binding isotherms are central features, and their implications need to be incorporated in current thinking. A variety of systems are described herein where catalyst complexity leads to broad, non-Langmuirian surface isotherms for the binding of hydrogen atoms – and this occurs even for ideal, flat Pt(111) surfaces. Modern catalysis employs nanoscale materials whose surfaces have substantial step, edge, corner, impurity, and other defect sites, and they increasingly have both metallic and non-metallic elements MnXm, including metal oxides, chalcogenides, pnictides, carbides, doped carbons, etc. The surfaces of such catalysts are often not crystal facets of the bulk phase underneath, and they typically have a variety of potential active sites. Catalytic surfaces in operando are often non-stoichiometric, amorphous, dynamic, and impure, and often vary from one part of the surface to another. Understanding of the issues that arise at such nanoscale, multi-element catalysts is just beginning to emerge. Yet these catalysts are widely discussed using Brønsted/Bell-Evans-Polanyi (BEP) relations, volcano plots, Tafel slopes, the Butler-Volmer equation, and other linear free energy relations (LFERs), which all depend on the implicit assumption that the active sites are all “similar” and that surface adsorption is close to ideal. These assumptions underly the ubiquitous intuition based on the Sabatier Principle, that the fastest catalysis will occur when key intermediates have free energies of adsorption that are not too strong nor too weak. Current catalysis research often aims to minimize the complexity of non-ideal isotherms through experimental and computational design (e.g., the use of single crystal surfaces), and these studies are the foundation of the field. In contrast, this Perspective argues that the heterogeneity of binding sites and binding energies is an inherent strength of these catalysts. This diversity makes many nanoscale catalysts inherently a high-throughput screen wrapped in a tiny package. Only by making the heterogeneity part of the foundation of catalysis models, sorting the types of active sites and dissecting non-ideal binding isotherms, will modern catalysis learn to harness the inherent diversity of real catalysts. Controlling rather than avoiding diversity is needed to optimize complex modern catalysts and catalytic conditions.

Zeolite-templated carbon synthesized with ion-exchanged FAU-zeolite using alkaline earth metal ions for the selective adsorption of C2 hydrocarbons over C1 hydrocarbon

In this study, zeolite-templated carbon (ZTC) was synthesized using ion-exchanged faujasite-Y (FAU, NaY) zeolites with different alkali earth metals (Mg2+, Ca2+, Sr2+, and Ba2+) to investigate the effects of these metals on the synthesis, characteristics, and C2/C1 hydrocarbon separation performance of ZTC. Thermogravimetric and temperature-programmed desorption of NH3 (TPD-NH3) analyses showed that carbon deposition tends to occur outside the pores because of the increasing number of moderate acid sites as the atomic number increases. In particular, in the case of FAU-ZTC(Ca) synthesized using CaY as the ZTC template, carbon accumulated inside the pores owing to the distribution of the appropriate acid strength, resulting in the highest specific surface area of 2,835 m2/g among the synthesized ZTCs. The combined X-ray photoelectron and Raman spectroscopy results confirm that these defect sites of ZTC act as adsorption sites for large molecules such as C2H4 and C2H6. The isothermal adsorption of CH4, C2H4, and C2H6 showed that FAU-ZTC(Ca) exhibited the highest adsorption capacity ratios of C2H4 and C2H6 to CH4, with a C2H6/CH4 ratio of 5.897 and C2H4/CH4 ratio of 5.288, respectively. The effective pore size ranges affecting the adsorption of CH4, C2H4, and C2H6 determined using linear regression analysis are 0.4 to 0.6 nm for CH4 and 0.6 to 1.1 nm for C2H4 and C2H6. Molecular simulations confirmed that the adsorption energy was maximized by the interaction between the hydrogen atoms of the hydrocarbons and the carbon atoms of ZTC. Furthermore, C2H4 and C2H6 require larger pores than CH4 adsorption because C2H4 and C2H6 prefer to lie horizontally rather than vertically in the pores of the ZTC.

Turbulent circumnuclear disc and cold gas outflow in the newborn radio source 4C 31.04

We present deep kiloparsec- and parsec-scale neutral atomic hydrogen (H I) absorption observations of a very young radio source (≤5000 years), 4C 31.04, using the Westerbork Synthesis Radio Telescope (WSRT) and the Global Very Long Baseline Interferometry (VLBI) array. Using z = 0.0598, derived from molecular gas observations, we detect, at both kpc and pc scales, a broad absorption feature (FWZI = 360 km s−1) centred at the systemic velocity, and narrow absorption (FWZI = 6.6 km s−1) redshifted by 220 km s−1, both previously observed. Additionally, we detect a new blueshifted, broad, shallow absorption wing. At pc scales, the broad absorption at the systemic velocity is detected across the entire radio source while the shallow wing is only seen against part of the eastern lobe. The gas has higher H I column density along the eastern lobe than along the western one. The velocity dispersion of the gas is high (≥40 km s−1) along the entire radio continuum, and is highest (≥60 km s−1) in the region including the outflow and the radio hot spot. While we detect a velocity gradient along the western lobe and parts of the eastern lobe at PA ∼ 5° −10°, most of the gas along the rest of the eastern lobe exhibits no signs of rotation. Earlier optical spectroscopy suggests that the optical AGN is very weak. We therefore conclude that the radio lobes of 4C 31.04 are expanding into a circumnuclear disc, partially disrupting it and making the gas highly turbulent. The distribution of gas is predominantly smooth at the spatial resolution of ∼4 pc studied here. However, clumps of gas are also present, particularly along the eastern lobe. This lobe appears to be strongly interacting with the clouds and driving an outflow ∼35 pc from the radio core, with a mass-outflow rate of 0.3 ≤ Ṁ ≤ 1.4 M⊙ year−1. It is likely that this interaction has caused the eastern lobe to be rebrightened, giving the source an asymmetric morphology. We compare our observations with the predictions of a recent analytical model regarding the survival of atomic gas clouds in radio-jet-driven outflows and find that the existence of a subkpc-scale outflow in this case could imply inefficient mixing of the cold gas with the hot medium and high gas density, leading to very short cooling times. Overall, our study provides further evidence of the strong impact of radio jets on the cold interstellar medium (ISM) in the early stages of their evolution and supports the predictions of numerical simulations regarding jet–ISM interactions and the nature of the circumnuclear gas into which the jets expand.