Narrow Pore Research Articles

Finely Tuning Metal Ion Valences of [Fe3-xMx(μ3-OH)(Carboxyl)6(pyridyl)2] Cluster-Based ant-MOFs for Highly Improved CO2 Capture Performances.

Solvothermal reactions of different trinuclear precursors and 5-(pyridin-4-yl)isophthalic acid (H2L) successfully led to four anionic ant topological MOFs as Fe3-xMx(μ3-OH)(CH3COO)2(L)2·(DMA+)·DMF [M = Mn(II), Fe(II), Co(II), x = 0, 1, 2 and 3], namely, NJTU-Bai79 [NJTU-Bai = Nanjing Tech University Bai's group, Mn3(μ3-OH)], NJTU-Bai80 [Fe2Mn(μ3-OH)], NJTU-Bai81 [Fe3(μ3-OH)], and NJTU-Bai82 [Fe2Co(μ3-OH)], which possess the narrow pores (2.5-6.0 Å). NJTU-Bai80-82 is able to be tuned to the neutral derivatives [NJTU-Bai80-82(-ox), ox = oxidized] with M2+ ions oxidized to M3+ ones in the air and the OH- ions coordinated on M3+ ions. Very interestingly, selective CO2/N2 adsorptions of NJTU-Bai80-82(-ox) are significantly enhanced with the CO2 adsorption uptakes more than about 6 times that of NJTU-Bai79. GCMC simulations further revealed that neutral NJTU-Bai80-82(-ox) supplies more open frameworks around the -CH3 groups at separate spaces to the CO2 gas molecules with relatively more pores available to them after the removal of counterions. For the first time, finely tuning metal ion valences of metal clusters of ionic MOFs and making them from electrostatic to neutral were adopted for greatly improving their CO2 capture properties, and it would provide another promising strategy for the exploration of high-performance CO2 capture materials.

Biomass-derived ultramicroporous carbon with narrow pore size distribution for record-high radon adsorption

Radon (Rn) is a radioactive noble gas and one of the primary culprits of lung cancer. Developing efficient adsorbents for Rn removal is of paramount importance, yet remains a daunting challenge due to the weak interaction between Rn and the adsorbent, particularly when low concentrations of Rn are present. Herein, a renewable biomass-derived carbon material consisting of rich ultramicropores was synthesized for record-high Rn adsorption under ambient condition. By meticulously selecting the carbonization precursor, chemical activator, and pyrolysis temperature, the optimized adsorbent, GC-700-2.4, exhibits a narrow pore distribution in the ultramicroporous range (<7 Å). The dynamic adsorption coefficient (Kd) of GC-700-2.4 is determined to be 9.51 L/g based on radon breakthrough experiments, which is twice the value of the commercial Rn adsorbent, coconut shell activated carbon (Kd = 4.65 L/g), and outperforms all other reported Rn adsorbents under comparable conditions. The superior Rn adsorption performance of GC-700-2.4 is attributed to the narrow ultramicropores in GC-700-2.4 that show enhanced confinement effect toward Rn. Consequently, GC-700-2.4 shows promising potential for practical applications as an efficient and cost-effective Rn adsorbent.

Selective hydrogenation of furfural to tetrahydrofurfuryl alcohol in isopropanol over hydrotalcite-derived nickel-based catalyst

A series of hydrotalcite-derived nickel-based catalysts were synthesized by coprecipitation, drying, calcination and reduction, and used for the selective hydrogenation of furfural to tetrahydrofurfuryl alcohol. Ni1Zr1Al2-R, with specific surface area (SBET) of 145.6 m2, narrow pore size distribution of 7.1 nm, and small Ni0 particle size of 7.31 nm, showed 100 % furfural conversion and 94.5 % tetrahydrofurfuryl alcohol selectivity under mild conditions (140 °C, 2 h). It was found that furfural was first hydrogenated to furfuryl alcohol, which was further hydrogenated to tetrahydrofurfuryl alcohol. XRD and TEM showed that Ni0 (111) plane played an important role on the catalytic hydrogenation process. Al increased the specific surface area (SBET) and total acid sites of the catalyst, providing more possibilities for the catalyst to contact the substrate. The introduction of Zr improved the ratio of medium acid sites and decreased the size of metal nickel particles, improving the resistance to carbon deposition and allowing the structure and catalytic performance to remain stable after five recycles.

Tailoring the pore size distribution of nanofiltration membranes via surfactants with different alkyl chain lengths: Towards efficient molecular separation

The diffusion of amine monomer during interfacial polymerization (IP) directly affects the structure and properties of the polyamide (PA) separation layer. Surfactants can regulate the diffusion rate of monomers and change the microstructure of the PA layer. In this study, a PA nanofiltration (NF) membrane with the tailor-made pore size is fabricated by modulating the diffusion rate of 1, 4, 7, 10-tetraazacyclododecane (Cyclen). Surfactants with different alkyl chain lengths are used to precisely regulate the diffusion rate of Cyclen monomer. The longer the alkyl chain length of the surfactant is, the faster the diffusion rate of the Cyclen monomer is, resulting in the formation of a PA layer with a narrow pore size distribution. The prepared composite membrane is qualified for on-demand desalting and antibiotic/salt separation performance by changing the length of the alkyl chain. For example, surfactants with short alkane chains (C4) endow the NF membranes with a high water permeance of 30.7 L−1 m−2h−1 bar−1 for tetracycline separation. Surfactants with long alkane chains (C12) endow the NF membranes with a high selectivity of 84.8 for tetracycline/NaCl separation. This study provides further evidence for surfactant-regulated IP reactions and offers new ideas for the tailor-made regulation of NF membrane properties.

Synthesis of hyperbranched polyethylene-graft-poly[3-ethyl-3-(methacryloyloxy)methyloxetane] via chain walking polymerization and ATRP for cationic photo-curing on membrane surface

Polyethylene is among the most widely-used coating materials due to the excellent physical and mechanical properties. However, the chemical inertness and poor solubility limit the application of polyethylene in coating. In this study, hyperbranched polyethylene-based graft copolymers containing functional oxetane groups (HBPE-g-POXMA) were synthesized via chain walking polymerization (CWP) and atom transfer radical polymerization (ATRP) in tandem. Macroinitiators were first synthesized via CWP of ethylene and trimethyl(undec-10-en-1-yloxy) silane following deprotection and esterification reaction. Subsequent ATRP of 3-ethyl-3-(methacryloyloxy) methyloxetane was performed to yield functional polyethylene with controlled molecular weight (MW), relatively narrow MW distribution, good solubility in organic solvents as well as pendant oxetane groups for photopolymerization. Finally, cationic photo-curing of HBPE-g-POXMA was conducted to build crosslinked polyethylene layers on polypropylene membrane surface. The composite membrane showed a narrow pore size distribution (0.03–0.63 μm) and an average pore size of merely 0.31 μm, which exhibited a retention ratio of over 90 % for different dyes. The strategy developed in this study could provide a synthetic route to hyperbranched polyethylene for functional coating via cationic photo-curing.

A bifunctional 3D porous MOF with potential for fluorescence sensing of picric acid and natural gas purification

A pillared-layer fluorescence metal-organic framework [Zn2(TCPP)(BPE), GXZ-1] has been synthesized by using the AIE ligand 2,3,5,6-tetrakis(4-carboxyphenyl) pyrazine (TCPP) and 1,2-Bis(4-pyridyl) ethylene (BPE). The GXZ-1 exhibited remarkable stability in both air and various solvents. Furthermore, fluorescence experiments demonstrated its potential as a fluorescence probe for the sensitive detection of picric acid (PA). Additionally, the activated GXZ-1 exhibited permanent porosity with a high BET surface area of 210.59 m2 g−1 and a narrow pore size distribution of 0.6 nm. These properties enable GXZ-1 ideally suitable for gas separation applications. Gas adsorption experiments revealed promising CO2/CH4 separation properties, with an IAST adsorption selectivity of 8.37 and 5.39 for equimolar CO2/CH4 gas mixtures at 273/298 K and 1 atm, respectively. In addition, GXZ-1 displayed outstanding chemical and thermal stability, further enhancing its potential for practical applications.

Nitrogen-doped porous carbon through K2CO3-activated bamboo shoot shell for an efficient CO2 adsorption

In this paper, a two-stage approach was employed to produce nitrogen-doped porous carbons from bamboo shoot shells. These shells were utilized as a cost-effective biomass resource for the production of activated carbon in gas adsorption. The initial step involved co-carbonization of the bamboo shoot shells with urea, followed by activation using potassium carbonate. A series of nitrogen-doped biochar was prepared by varying the activation temperature and activator ratio. This approach allowed for the investigation of their potential in capturing CO2. Surface analyses were conducted using BET, SEM, and TEM techniques to examine the structural evolution of nitrogen-doped biochar. The results revealed that the fibrous structure of the bamboo shoot shells was well-preserved after carbonization and nitrogen doping, while activation resulted in the formation of a distinct worm-like microporous structure. Among them, the sample BNC-800-2 possessed the largest specific surface area of 1985 m2/g. Notably, the nitrogen-doped biochar activated at 800 °C exhibited remarkable capacity for adsorbing carbon dioxide, with values of 7.52 mmol/g and 3.60 mmol/g at 1 bar and temperatures of 0 °C and 25 °C, respectively. The adsorbent also demonstrated excellent cyclic stability and selectivity for gas mixture (CO2 and N2), attributed to its large specific surface area and narrow pore size, which synergistically contributed to its performance. Furthermore, the adsorption equilibrium was analyzed using the Langmuir and Freundlich isotherm models, with the experimental data showing significant agreement with the Freundlich isotherm model. Additionally, thermodynamic calculations confirmed that the adsorption process of CO2 on nitrogen-doped biochar was spontaneous and exothermic, indicating physical adsorption. This further validates the efficacy of the adsorbent in capturing CO2. This study demonstrates the potential of bamboo shoot shells as a low-cost biomass resource for producing effective adsorbents for CO2 capture.

Comprehensive Molecular Dynamics Study of Oxygen Diffusion in Carbon Mesopores: Insights for Designing Fuel-Cell Catalyst Supports.

Mesoporous carbon is often used as a support for platinum catalysts in polymer electrolyte fuel-cell catalyst layers. Mesopores in the carbon support improve the performance of fuel cells by inhibiting the adsorption of ionomer onto the catalyst particles. However, the mesopores may impair mass transport. Hence, understanding molecular behaviors in the pores is essential to optimizing the mesopore structures. Specifically, it is crucial to understand the oxygen transport in the high-current region. In this study, the diffusion coefficients of oxygen molecules in carbon mesopores were calculated for various pore lengths, pore diameters, filling rates, and water contents in the ionomer via molecular dynamics simulations. The results show that oxygen diffusion slows by 2 orders of magnitude because of pore occlusion, and it slows down by an additional 1 or 2 orders of magnitude if ionomers are present in the pores. The occlusion can be theoretically predicted by considering the surface free energy. This theory provides some insight into mesoporous carbon designs; for instance, the theory suggests that narrow pores should be shortened to prevent occlusion. Slow diffusion in the presence of ionomers was attributed to the localization of oxygen at the dense ionomer-carbon interface. Thus, to improve oxygen transport properties, carbon surfaces and ionomer structures may be designed in such a manner as to prevent densification at the interface.

Hierarchically Porous Covalent Organic Frameworks: Synthesis Methods and Applications.

Covalent organic frameworks (COFs) with high porosity have garnered considerable interest for various applications owing to their robust and customizable structure. However, conventional COFs are hindered by their narrow pore size, which poses limitations for applications such as heterogeneous catalysis and guest delivery that typically involve large molecules. The development of hierarchically porous COF (HP-COF), featuring a multi-scale aperture distribution, offers a promising solution by significantly enhancing the diffusion capacity and mass transfer for larger molecules. This review focuses on the recent advances in the synthesis strategies of HP-COF materials, including topological structure design, in-situ templating, monolithic COF synthesis, defect engineering, and crystalline self-transformation. The specific operational principles and affecting factors in the synthesis process are summarized and discussed, along with the applications of HP-COFs in heterogeneous catalysis, toxic component treatment, optoelectronics, and the biomedical field. Overall, this review builds a bridge to understand HP-COFs and provides guidance for further development of them on synthesis strategies and applications.

ZnO-PANI nanocomposite: Enhanced electrochemical performance towards energy storage

In the present investigation a novel nanocomposite composed of Polyaniline (PANI) and Zinc Oxide (ZnO) has been evaluated for its structural, morphological, and electrochemical properties for its application as high-performance Li-ion battery electrode. The X-ray diffraction (XRD) and Furrier transform infrared (FTIR) spectral analysis confirmed the synthesis of ZnO-PANI nanocomposite. The Field emission- scanning electron microscopy (FE-SEM) images confirmed the uniform distribution of ZnO nanoparticle in PANI matrix, while BET surface area analysis revealed a narrow mesoporous pore distribution with high surface area, enhancing its potential for energy storage. The electrochemical assessment using CR2032 coin cells showcased the remarkable performance of the ZnO-PANI nanocomposite as an electrode material for energy storage. Cyclic voltammetry (CV) analysis revealed distinct reduction and reformation peaks related to ZnO and Li+ insertion into the PANI matrix. The nanocomposite displayed a high specific capacity, with an initial discharge capacity of 1052 mA h g−1, followed by stable performance in subsequent cycles. Notably, Coulombic efficiency consistently exceeded 98 % from the 10th cycle, demonstrating excellent performance. The rate capability was equally impressive, delivering discharge capacities from 1052 mA h g−1 at 0.1C to 771 mA h g−1 at 2C. Long-term cycling tests illustrated exceptional capacity retention, with 92.99 % capacity retained after 500 cycles and outstanding Coulombic efficiency consistently above 99 %. In conclusion, the ZnO-PANI nanocomposite exhibits desirable structural and morphological attributes, exceptional electrochemical performance, and potential for advanced energy applications, particularly in Li-ion batteries.

Enhanced performance polyamide membrane by introducing high-porosity SOD/GO composite interlayer to tailor the interfacial polymerization process

Controllable preparation of high-performance polyamide nanofiltration (NF) membranes that can be used in various applications such as seawater desalination and wastewater treatment is very promising. In this work, a high-performance polyamide NF membrane was designed using high-porosity hydroxy sodalite/graphene oxide (SOD/GO) composite interlayer to slow down the diffusion of amine monomer and control the interfacial polymerization (IP) process. The unique tortuous effect and hydrogen bonds with amine monomers caused by the dense interlayer significantly inhibit the diffusion of amine monomers (reduction of 50 % in diffusion rate), thereby resulting in the controllable slow IP process. The slowing IP process facilitates the formation of thinner dense polyamide (PA) layer with stripe morphology and narrow pore size. Consequently, the optimal polyamide membrane with composite interlayer possesses a superior water permeability of 22.05 L m-2h−1⋅bar−1, nearly 2.5 fold that of the controlled one, while retaining an excellent rejection of Na2SO4 (97.25 ± 0.81 %). Moreover, the polyamide membrane depicts outstanding antifouling propensity (flux-recovery ratio (FRR) = 82 %), long-term stability (80 h) and pressure resistance (9 bar). This work provides a novel strategy for controllable construction of high-performance NF membrane and deepens the slights into the interlayer influences IP process.

Dynamic gas liberation from water-immersed anthracite coal with varying wetting states under heating conditions: Unveiling the gas breakthrough phenomena

During coalbed methane recovery, the effective extraction of gas trapped in narrow pore throats encounters challenges due to the water blocking effect. To shed light on this phenomenon during thermal recovery of coalbed methane, this study investigated the breakthrough behaviors of CO2 traversing through a 0.2 mm diameter hole in water-immersed anthracite coal at varying temperatures (23 °C, 40 °C, and 60 °C). The measurements of breakthrough pressure (defined as the pressure at which the bubble achieves a semi-spherical shape with a minimum curvature radius), growth characteristics of CO2 bubbles, and coal wettability were conducted under varying thermal conditions and water immersion durations. The results showed that the breakthrough pressure initially increased continuously as water immersed into the coal and then gradually stabilized. During this process, the coal's water wettability increased, leading to a decrease in the diameter of the bubble's three-phase contact line, which in turn affected the breakthrough pressure. Moreover, higher temperatures accelerated the rate of water immersion, augmenting the coal's hydrophilicity. The elevated temperature also resulted in a decrease in water surface tension, consequently contributing to a lower breakthrough pressure. Interestingly, compared to CO2, He exhibited a faster increase in breakthrough pressure during water immersion. This disparity can be attributed to He's superior diffusion capacity and lower viscosity, enabling a swifter transformation of the coal's wetting state during water imbibition. This study revealed the dual mechanism of heating to reduce gas breakthrough pressure, as well as the effects of surface water content and gas properties. These findings highlight potential benefits of thermal treatment on coalbed methane recovery and provide valuable insights for its exploitation under different geological conditions.

Mesoporous organosilicas with highly-content tyrosine framework as extractive phases for non-steroidal anti-inflammatory drugs in aquatic media

BackgroundAttentions regarding ordered mesoporous silica materials (OMSs), with large specific surface areas and narrow pore size distribution, which are prepared via self-assembly techniques, have been raised in sorption, separation, and sample preparation. However, in order to extend and improve their applications, a functionalization step is required. Organic units can be anchored on the inner or outer surface as well as in the silica wall framework by co-condensation-, grafting-, and periodic mesoporous organosilica (PMO) preparation approaches. Apparently, by synthesizing PMO with extensive and flexible organic bridging groups within the mesoporous wall, an efficient extractive phase can be achieved. ResultsWe employed tyrosine amino acid to synthesize a PMO-based extractive phase. The FT-IR, 1H NMR, HR-ESI-MS, Low angle-XRD, TEM, FESEM, BET, and EDX-MAP analyses confirmed the successful synthesis of PMO within the salt-assisted templating method. A comprehensive study on sorption behavior of PMO was performed and its efficiency was evaluated against the grafting and co-condensation methods. Then, it was implemented to the pipette tip-micro solid phase extraction (PT-μ-SPE) of widely used non-steroidal anti-inflammatory drugs (NSAIDs) in water/wastewaters. Limits of detection and quantification were obtained in the range of 0.1–1.5 and 0.3–5 μg L−1, respectively. The calibration plots are linear in the 1–1000, 3–1000, 10–750, and 3–750 μg L−1, respectively. The intra-and inter-day precision at 50 and 200 μg L−1 levels are 2.9–7.1 % and 3.5–8%, while recoveries are between 84 and 111 %. SignificanceHigh-capacity tyrosine functionalized PMO with 2D hexagonal symmetry silica mesoporous structures found to be highly efficient extractive media. Despite the bulkiness and flexibility of the bridging group within the mesoporous wall, the synthesis condition was optimized in order to load more organic content in the PMO structure. The PMO performance was superior over organically modified ordered mesoporous silica materials prepared by the grafting and co-condensation methods.

Utilizing EPR spectroscopy to investigate the liquid adsorption properties of bimetallic MIL-53(Al/Cr) MOF.

The flexibility of the MIL-53(M) metal-organic framework (MOF) has been elucidated through various characterization methodologies, particularly in gas and liquid adsorption processes. However, to the best of our knowledge, there has been no prior electron paramagnetic resonance (EPR) characterization of liquid-phase adsorption in the MOF MIL-53(M), which offers insights into local geometric changes at the oxygen octahedron containing the metal ions of the framework. In this study, we investigate, for the first time, the pore transformations within the MIL-53(Al0.99Cr0.01) framework during liquid-phase adsorption using EPR spectroscopy. Our investigation concentrates explicitly on the adsorption of pure solvents, including water, methanol, ethanol, isopropanol, pyridine, and mixed water/methanol phases. The EPR spectroscopy on the (Al0.99Cr0.01) MOF has allowed us to witness and comprehend the transitions between the narrow pore and large pore phases by examining changes in the zero-field splitting parameters of the S = 3/2 Cr(iii) species. Of all the solvents examined, a robust and distinct spectral feature observed during methanol adsorption unequivocally indicates the pore opening.

Experimental and model analysis of the effect of pore and mineral characteristics on fluid transport in porous soil media

The fluid transport in porous media is a critical property for oil and gas exploitation, construction engineering, and environmental protection. It is profoundly influenced by pore geometry and mineral properties. Currently, the Kozeny–Carman equation serves as the permeability prediction equation for porous media, established on the circular pores model. However, it fails to fully account for the impact of pore shape and mineral properties of the soil, leading to significant deviations between predicted and measured soil permeability results. In this paper, based on scanning electron microscope image and mercury intrusion porosimetry, the pores were divided into circular pores and narrow slit pores according to the ratios of pore area and circumference. Then, the quantitative expression of the two types of pores and their connectivity and tortuosity were given, and the circular and narrow slit composite pore model was used to describe the soil pore. Subsequently, the electrostatic potential of pore water was calculated by the Poisson–Boltzmann equation to consider the adsorption effect of minerals on pore water. Combined with the Navier–Stokes equation, the permeability prediction equation considering pore geometry, pore connectivity, and tortuosity and mineral properties was established. Finally, the experimental results illustrated that the theoretical prediction results were in good agreement with the experimental results. The proposed permeability prediction equation proves valuable for assessing and predicting the fluid transport in porous media.

Orientational transitions of discotic columnar liquid crystals in cylindrical pores.

Confined in a cylindrical pore with homeotropic anchoring condition, the hexagonal columnar phase of discotic liquid crystals can form a "log-pile" configuration, in which the columns are perpendicular to the long axis of the pore. However, the {100} planes of the hexagonal lattice can orient either parallel (termed (100)‖ orientation) or perpendicular ((100)⊥) to pore axis. Here we experimentally show that the (100)‖ orientation is found in narrower cylindrical pores, and the (100)‖-(100)⊥ transition can be controlled by engineering the structure of the molecules. The (100)‖ orientation is destroyed in asymmetric discotics hepta(heptenyloxy)triphenylene (SATO7); replacing the oxygen linkage in hexa(hexyloxy)triphenylene (HATO6) by sulphur (HATS6) improves the (100)‖ orientation in small pores; adding a perfluorooctyl end to each alkyl chain of HATO6 (HATO6F8) moves the (100)‖-(100)⊥ transition to larger pores. We have provided a semi-quantitative explanation of the experimental observations, and discussed them in the context of previous findings on related materials in a wider pore size range from 60 nm to 100 μm. This allows us to produce a comprehensive picture of confined columnar liquid crystals whose applications critically depend on our ability to align them.

Synthesis of Cadmium Oxyorthosilicate by a Sol-Gel Method

Cadmium silicates are materials of interest due to their stability and possible application as phosphors. There are three stable forms: cadmium metasilicate, CdSiO3, cadmium orthosilicate, Cd2SiO4 and cadmium oxyorthosilicate, Cd3SiO5. Of these, oxyorthosilicate is particularly challenging to obtain, leading to fewer studies. We have successfully prepared Cd3SiO5 using a sol-gel approach, employing cadmium acetate and tetraethylorthosilicate as precursors in a stoichiometric proportion of 2:1. Additionally, cetyltrimethylammonium bromide served as a template for creating a mesoporous structure. Adjusting the pH to 3 and subjecting the material to calcination at 800 °C for 6 h, we achieved the formation of cadmium oxyorthosilicate compound, identified by X-ray diffraction. Electron diffractometry and energy dispersive X-ray spectrometry confirm the phase purity. Characterization via nitrogen adsorption analysis and transmission microscopy shows aggregates of nanoparticles with a surface area of 6 m2 g-1 and a narrow pore diameter distribution centered at 5 nm.

Enhancing Adrenaline Sensing with Lanthanum Cuprate: A Promising Approach for a Novel Sensor

Electrochemical sensing is an excellent analytical means with multiple applications. Most of the electrochemical developments are based on the novel electrochemically active substrates. A lot of them have been adopted from other fields of material science. Every new class of functional materials has impacted on the development of electroanalytical chemistry. In this view, lanthanide cuprates, a well recognized high temperature superconducting materials were considered for adrenaline sensing. Obtained from corresponding oxides, a highly crystalline La2CuO4 found to be a suitable substrate for analytical method development. It inherited sponge-like morphology common for the most of the previously reported lanthanum cuprates with narrow pore size distribution at 400–700 nm. Excellent charge mobility and low resistivity provided a carbon paste electrode with improved linearity range and low limit of detection. Repeatability and stability of the developed sensor were at satisfactory level. Sensor functionality was verified on the real samples with excellent recovery rates. With this work we suggest further development of electroanalytical methods with application of lanthanide cuprates.

Soybean hulls activated carbon for metronidazole adsorption: Thermochemical conditions optimization for tailored and enhanced meso/microporosity

In this work, the use of soybean hulls as a residual biomass precursor for highly porous carbon materials through thermochemical treatments was assessed, aim to modify the surface chemistry and obtain enhanced chemistry and textural properties for the metronidazole (MTN) drug adsorption. Initially, the biomass was subjected to different chemical treatments followed by pyrolysis under fixed conditions. The modified carbon materials were evaluated in terms of residual surface charge, surface chemistry, and adsorption capacity. After determining the most appropriate chemical treatment, the optimized thermochemical conditions were investigated. Remarkable textural properties (Stotal= 1355.7 m2 g−1) of the activated carbon derived from dilute acid-alkali combined treatment (AC-CT) were achieved under the following conditions: T = 925 °C; t = 145 min and C= 0.3 mol L−1, which led to an increase in the adsorption capacity up to q= 51.25 mg g−1 (50% higher than the biochar). This increase in MTN adsorption performance is possibly related to the increase in the micropore area (SMICRO= 800.7 m2 g−1) and volume values, in addition to a tailored and narrow pore size distribution with an adequate size ratio to the MTN molecule (ØP/ØMTN= 2.3 – 2.6). Based on the results, it was identified that this tuned pore size distribution and the presence of surface oxygen groups provided adequate affinity to the MTN molecule due to H–bonds, π–interactions, and pore-filling effect retention mechanisms.

MgH2 nanoparticles confined in reduced graphene oxide pillared with organosilica: a novel type of hydrogen storage material.

Hydrogen is a promising alternative fuel that can push forward the energy transition because of its high energy density (142 MJ kg-1), variety of potential sources, low weight and low environmental impact, but its storage for automotive applications remains a formidable challenge. MgH2, with its high gravimetric and volumetric density, presents a compelling platform for hydrogen storage; however, its utilization is hindered by the sluggish kinetics of hydrogen uptake/release and high temperature operation. Herein we show that a novel layered heterostructure of reduced graphene oxide and organosilica with high specific surface area and narrow pore size distribution can serve as a scaffold to host MgH2 nanoparticles with a narrow diameter distribution around ∼2.5 nm and superior hydrogen storage properties to bulk MgH2. Desorption studies showed that hydrogen release starts at relatively low temperature, with a maximum at 348 °C and kinetics dependent on particle size. Reversibility tests demonstrated that the dehydrogenation kinetics and re-hydrogenation capacity of the system remains stable at 1.62 wt% over four cycles at 200 °C. Our results prove that MgH2 confinement in a nanoporous scaffold is an efficient way to constrain the size of the hydride particles, avoid aggregation and improve kinetics for hydrogen release and recharging.