Hierarchical Mesoporosity Research Articles

Multifunctional and Hierarchical Porous ZIF-8: Amine and Thiol Tagged via Mixed Multivariate Ligand Strategies for Enhanced CO2 and Iodine Adsorption.

This study demonstrated a simple and innovative way of using the direct de novo synthesis to fabricate the mesoporous structure and diverse functionality of ZIF-8 for environmental cleanup and gas storage applications. By introducing different ligands, we have developed a version of ZIF-8 that could better capture carbon dioxide (CO2) and iodine. The ZIF-8 was successfully designed to have the hierarchical and mesoporous structure with the functional groups of amine and thiol groups by adjusting the pKa values (from 8 to 12) of ligand instead of the original ligand, 2-methyl imidazole (Hmim, pKa~14.2). The modulation of ZIF-8 particle size, porosity, and functional characteristics was achieved through varied ligands and their concentrations, streamlined into a single and room-temperature synthesis condition. The resulting ZIF-8 materials exhibit intricate hierarchical architectures and a high density of functional groups, significantly enhancing molecular diffusion and accessibility. Among the developed materials, ZIF-8-AS, featuring both amine and thiol groups, demonstrates the fastest adsorption kinetics and a twofold increase in iodine adsorption capacity (qm=1101.5 mg g-1) compared to ZIF-8 (qm=514.3 mg g-1). Furthermore, the hierarchical mesoporosity of ZIF-8-A-10.1 improves CO2 adsorption to 1.0 mmol g-1 at 298 K, which is 1.3 times higher than that of the microporous ZIF-8.

Iron carbide anchored on N-doped hierarchically porous carbon core/shell architecture for highly efficient OER water splitting

Metal-nitrogen-carbon complexes are emerging as efficient electrocatalysts for the oxygen evolution reaction (OER) owing to the excellent activity, stability, natural abundance, and cost-effectiveness of these complexes. This study introduces an innovative approach to synthesizing an N-doped porous graphitic carbon with a Fe3C core-shell structure (N-PGC@Fe3C) using biomass-derived carbon. Characterized by a large specific surface area of 3169 m2/g and hierarchical mesoporosity, the synthesized N-PGC@Fe3C catalysts demonstrate superior OER activity, achieving low overpotentials of 143.8 and 312.2 mV at current densities of 20 and 50 mA/cm2, respectively, in a 1 M KOH electrolyte. Notably, the N-PGC@Fe3C-3 exhibits outstanding cycle performance after 2000 cycles. Density functional theory calculations confirm that the core-shell-structured N-PGC@Fe3C provides the primary active site for the OER. The observed efficiency is attributed to the synergistic action of the Fe–N–C active sites, ultrafine Fe3C encapsulation, and the hierarchical porous nanosheet structure that facilitates mass diffusion and increases the exposure of active sites. Furthermore, when employed as an anode during overall water splitting, N-PGC@Fe3C achieves a cell voltage of 1.49 V at a current density of 10 mA/cm2 under alkaline conditions. This study can facilitate the development of high-performance Fe–N–C-based catalysts and clarify the underlying OER mechanisms, thereby advancing the field of electrocatalytic water splitting and energy storage systems.

Catalytic Cracking of 1,3,5‐Triisopropylbenzene and Low‐Density Polyethylene over Hierarchical Y Zeolites and Al‐SBA‐15

AbstractCatalytic cracking of high molecular weight hydrocarbons underpins the production of fossil fuels from petroleum vapour and the recycling of polyolefin waste plastic. However, thermal cracking over conventional microporous solid acids is hindered by poor mass‐transport. Here we explore the performance of hierarchical H−Y zeolites and Al‐SBA‐15 for the catalytic cracking of 1,3,5‐triisopropylbenzene (1,3,5‐TIPB) and low‐density polyethylene (LDPE) in a continuous fixed‐bed flow reactor. Dealumination by acid washing was used to create hierarchical mesoporosity in H−Y zeolite and modify the solid acidity. Physicochemical properties were studied by X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), gas adsorption, in‐situ Fourier transform infrared (FTIR), ex‐situ pyridine DRIFT, 29Si and 27Al nuclear magnetic resonance (NMR), and 1H relaxation and pulsed field gradient (PFG) NMR diffusion studies. Despite weakening acidity, the introduction of hierarchical porosity promotes deep cracking of both feedstocks; HNO3 dealuminated H−Y produces five times more cumene and benzene from 1,3‐5‐TIPB, and 33 % more benzene and xylenes from LDPE, than the parent H−Y.

Efficient removal of nanoplastics from water using mesoporous metal organic frameworks

Nanoplastics have garnered significant global attention as emerging environmental contaminants due to their susceptibility to be internalized by organisms, potentially leading to higher ecological and health risks compared to microplastics. Recently, adsorption has emerged as a promising strategy for nanoplastic removal, and new adsorbents have demonstrated impressive performance in this regard. In this study, we focused on the removal of polystyrene nanoplastics (NPs) from aqueous environments using a series of mesoporous Metal Organic Frameworks (MOFs). We synthesized mesoporous UiO-66 and its derivatives (–OH and –NH2) through direct solvothermal synthesis in the presence of cetyltrimethylammonium bromide (CTAB) or Pluronic-type triblock copolymer (P123). The resulting materials had high crystallinity and displayed a hierarchical mesoporosity. Remarkably, we found that UiO-66-NH2/P123 demonstrated exceptional efficiency in removing NPs, achieving up to 100 % removal efficiency at an initial concentration of 1 g·L-1. This indicates its potential as a highly effective adsorbent for nanoplastic removal from aqueous media.

Sub-micron sized hierarchical porous ZSM-5 particles with controllable mesoporous structures by changing the alkalinity in the synthesis using NaOH

This work reports that sub-micron sized hierarchical porous ZSM-5 particles with controllable mesoporous structures can be facilely synthesized in a seed-assisted system without using any secondary templates or organic additives. The results showed that typical samples so-obtained display relative uniform ellipsoidal sub-micron sized particles consisting of loosely packed primary nanocrystals. The mesoporous structures of ZSM-5 zeolite particles can be effectively introduced and adjusted by solely changing the quantity of NaOH in the initial synthesis mixture. The NaOH dosages significantly affect not only hierarchical mesoporosity but also the ratio of Si/Al and thus acidity of the final ZSM-5 product. Moreover, the effect of synthesis hydrothermal procedure was also investigated. The typical sample Z5-0.12 possesses high crystallinity, BET surface area, well-developed mesoporosity and improved catalytic performance in LDPE cracking. This approach constitutes a facile and cost-effective pathway to prepare sub-micron sized hierarchical porous ZSM-5 particles and might promote their application in industry.

Facile fabrication of mesoporosity silica as support for solid amine CO2 adsorbents with enhanced adsorption capacity and kinetics

Solid amine adsorbents show the excellent capture performance in flue gas CO2 separation. The pore structure of adsorbent plays a crucial role in improving adsorption performance. Herein, hierarchical mesoporous silica (HMS) support with large pore volume was prepared via one template without resorting to either additives or multi-templates. The pore structure of HMS support for polyethyleneimine (PEI) resulted in larger CO2 adsorption capacity and faster adsorption kinetics when compared to the SBA-15 support with the same amount of PEI loading. At the optimal PEI loading of 70 wt% on HMS, CO2 adsorption amount is 4.21 mmol/g at 75 °C with 15 vol% CO2. Simultaneously, HMS-PEI70% adsorbent is proved to be good stability during 20 adsorption cyclic. These results demonstrate that supports with hierarchical mesoporosity provide significant advantages for CO2 capture. Finally, considering the practical application of adsorbent, the influence of capture temperature and impurity gas on capture performance has been further investigated. CO2 adsorption capacity was enhanced with the presence of water, while the SO2 has the negative effect on the capture performance due to the competitive adsorption of sulfur dioxide. This work can provide a promising composite adsorbent to realize the efficient CO2 separation from the flue gas in the future.

Transition-metal doped titanate nanowire photocatalysts boosted by selective ion-exchange induced defect engineering

Defect engineering through elemental doping is an efficient way to boost the performance of semiconductor photocatalysts. Herein, transition-metal (TM) doped titanate nanowires (TNWs) were prepared via ion-exchange over the titanate precursors and demonstrated for the Rhodamine B (RhB) degradation under ultraviolet (UV) light irradiation. The ion-exchange of selective ions (V5+, Cr3+, Ni2+, and Zn2+) with protons from pristine TNWs resulted in the hierarchical meso-porosity of nanowires with large pores of ∼5–20 nm by TM doping and small pores of ∼3.6–4.5 nm inherited from pristine TNWs, which facilitates the mass transfer while maintaining high surface area and active sites. Meanwhile, the TM intercalation partially reduces the Ti4+ to Ti3+ and narrows the optical bandgap, which, together with oxygen vacancies and superoxide radicals from pristine TNWs, enhance the adsorption and photocatalytic degradation performance of RhB. This work helps to elucidate the effects of transition-metal doping and provides a rational strategy towards high performance titanate-based photocatalysts for efficient and sustainable wastewater treatment.

Self-assembled mesostructured Co0.5Fe2.5O4 nanoparticle superstructures for highly efficient oxygen evolution

Self-assembly of colloidal nanoparticles (NPs) into well-defined superstructures has been recognized as one of the most promising ways to fabricate rationally-designed functional materials for a variety of applications. Introducing hierarchical mesoporosity into NP superstructures will facilitate mass transport while simultaneously enhancing the accessibility of constituent NPs, which is of critical importance for widening their applications in catalysis and energy-related fields. Herein, we develop a colloidal co-assembly strategy to construct mesostructured, carbon-coated Co0.5Fe2.5O4 NP superstructures (M-C@CFOSs), which show great promise as highly efficient electrocatalysts for the oxygen evolution reaction (OER). Specifically, organically-stabilized SiO2 NPs are employed as both building blocks and sacrificial template, which co-assemble with Co0.5Fe2.5O4 NPs to afford binary NP superstructures through a solvent drying process. M-C@CFOSs are obtainable after in situ ligand carbonization followed by the selective removal of SiO2 NPs. The hierarchical mesoporous structure of M-C@CFOSs, combined with the conformal graphitic carbon coating derived from the native organic ligands, significantly improves their electrocatalytic performance as OER electrocatalysts when compared with nonporous Co0.5Fe2.5O4 NP superstructures. This work establishes a new and facile approach for designing NP superstructures with hierarchical mesoporosity, which may find wide applications in energy storage and conversion.

Microstructured poly(ether-ether-ketone)-hydroxyapatite composites for bone replacements

Utilizing a novel processing method of PEEK foam that produces hierarchical mesoporosity, we explore the use of hydroxyapatite (HA)/PEEK composites for mimicking the structure of human bone. The effect of HA content and processing parameters on the porosity, and interconnective network are studied with respect to the corresponding morphology, mechanical properties, and ultimately the cell viability. Having achieved hierarchical structuration with pore sizes ranging from approx. a hundred nanometers all the way to a few hundred microns, the HA/PEEK composites produced desirable mechanical properties and promising cell proliferation. A strong correlation was not seen with HA loading and the resulting properties, but a combination of the HA loading and variance in porosity is shown to be significant. The development and analysis of this bone mimic structure opens up the potential for this processing method and material as a treatment to bone injuries and bone diseases.

Highly efficient thermo-electrochemical energy harvesting from graphene–carbon nanotube ‘hybrid’ aerogels

Three-dimensional scaffold assemblies consisting of thermally reduced graphene oxide nanosheets and small-diameter carbon nanotubes were synthesized as potential ‘all carbon’ thermo-electrochemical energy harvesters. The facile hydrothermal–solvothermal synthesis route in which organic wet chemistry used was to inter crosslink the well-dispersed graphene oxide nanosheets with carbon nanotubes followed by freeze-drying to produce monolithic aerogel networks with ultralow densities, tunable mesoscopic pore sizes, tailorable functionality and morphology. They exhibited high electrical conductivity due to multiplex topologies owing to the integration with carbon nanotubes, which has high density of states at van Hove singularities, accompanied by expected larger surface area and sufficient edge plane sites, which in-turn enhance surface adsorption and rapid ion transportation. We conducted thermoelectric and thermo-electrochemical power generation from these ‘hybrid’ aerogel materials and using two different designs of galvanic thermo-cells. Consequently, higher Seebeck (electronic; Se as well as ionic; Sion) coefficients and thermopower generation was measured that confirmed low thermal responsiveness attributed to smaller domain size generated by hierarchical mesoporosity and open network. These multiple features demonstrate significant potential of these novel electrodes in galvanic thermocells for low-grade thermal energy harvester with higher relative conversion efficiency.

Hierarchical mesoporous silica templated by the combination of fine emulsion and micelles

Abstract Concentrated emulsions have been widely considered as templates for the preparation of macroporous structures. Replacing concentrated emulsions by fine ones should rather lead to materials having large mesopores. However, fine emulsions were barely investigated for this purpose. On the other hand, mesostructured silica SBA-15 can be prepared from Pluronic P123 micelles according to the cooperative templating mechanism. Starting from mixture of fine emulsion and Pluronic P123 micelles, it is expected to obtain silicas with a controlled hierarchical mesoporosity. The fine emulsion has been formulated from the Kolliphor/Myristate/Water system. To get informations concerning the degree of compatibility between the two surfactants, which can affect the formation of the porous materials, the Kolliphor/P123/water system has been investigated in detail. The structural parameters of the mixed liquid crystal phases have been determined and the mixed micellar structure has been investigated by SAXS. The hierarchical porous silicas have been synthetized combining fine emulsion and Pluronic micellar solution. The materials porosity features strongly depend on the weight proportion between the fine emulsion and the P123 micelles. If this proportion is lower than 5/5, mesoporous silicas present a dual mesoporosity. By contrast, by increasing this proportion the mesopore size distribution only shows large mesopores.

Glucose-Mediated Synthesis of Hierarchical Porous ZnGa2O4 Microspheres for Effective Photocatalytic Removal of Aromatic and Arsenic Pollutants

Porous ZnGa2O4 microspheres (P-ZGO) are synthesized by a facial glucose-mediated microwave hydrothermal method followed by annealing. The morphological, photoelectric and photocatalytic properties of the as-prepared P-ZGO sample are characterized in detail, and the results show that the P-ZGO photocatalyst has a good crystallinity, large species surface area, hierarchical mesoporosity, and distinguished photoelectric properties. Under 254 nm UV irradiation, the P-ZGO sample shows a much higher activity and stability than TiO2 in the photocatalytic degradation of gas-phase aromatic pollutants. The average conversion efficiencies of toluene and benzene over P-ZGO are ~56.6% and ~44.3%, and with corresponding mineralization rates of ~86.3% and ~65.2%, respectively. No remarkable deactivation of P-ZGO is observed in a 60 h heterogeneous photoreaction. Furthermore, the as-prepared P-ZGO sample also shows an excellent photocatalytic efficiency (up to 99.8%) for the liquid-phase As(III) removal from water. The distinguished photocatalytic performance of P-ZGO can be ascribed to its unique electronic structures and hierarchical morphologies. According to the results of our analysis, a possible mechanism is also proposed to elaborate the photocatalytic oxidation process in the pollutants/P-ZGO system.

Interplay of topologically interconnected mesoporous network and defects number density in improving electroactivity of graphene-single-walled carbon nanotube aerogels

Electroactivity of graphene-family nanomaterials and three-dimensional porous architectures is key for various applications at the grand challenges of “energy-water-sensing nexus.” It requires well-controlled morphology, manipulation of surface chemistry, interconnected topologic network, as well as electronic properties. Here, we demonstrate by taking advantage of hierarchical mesoporosity, optimized defects number density, nD (edges-plane and pore sites, oxygenated and nitrogenated functionalities), further invoked by synergistic coupling between one-dimensional single-walled carbon nanotube (SWCNT) as “nano” spacers and polymer linker with two-dimensional reduced graphene oxide derived three-dimensional scaffolds (known as aerogels) under hydrothermal conditions, and improved electrochemical (re)activity by enhancing the heterogeneous electron transfer rate (kET). We determined the correlation among nD, in-plane sp2C cluster, La and interdefect distance, LD (all via Raman spectroscopy), and kET (via scanning electrochemical microscopy) to establish “structure–property–functionality–electroactivity” relationships. The prominent Raman bands were also analyzed to determine the sp2-bonded C cluster size (La) for graphene- and nanotube-rich phases. The interplay of (1) rich surface redox chemistry due to carbonyl—C=O, carboxyl—COOH, pryridinic—N and pyrrolic—N functional groups, and geometric defects; (2) protruded edge plane and nanopores sites; (3) topological network; and (4) finite density of states with increased vacancy sites is emphasized and signifies the inherently activated electronic states in functionalized nanoporous composite carbon aerogels, for improved physicochemical processes (following graphene < N-graphene < graphene-SWCNT < N-graphene-SWCNT aerogels) relevant for electrocatalysis, thermo-electrochemical energy harvesting, desalination, and biosensing.

On the effect of mesoporosity of FAU Y zeolites in the liquid-phase catalysis

The porosity and acidity of three commercial FAU Y zeolites (including the original HY-2.6 and dealuminated HY-15/-30 zeolites) were studied comprehensively using nitrogen (N2) physisorption, and mercury (Hg) porosimetry, ammonia temperature-programmed desorption (NH3-TPD) and pyridine Fourier transform infrared (pyridine-IR) analyses. The combined N2 physisorption and Hg porosimetry is a useful tool to evaluate the hierarchical mesoporosity in the dealuminated samples, revealing that HY-15 and HY-30 possess >50% open mesoporosity in the mesopores range of 5–10 nm. The acidity of the dealuminated Y zeolites has been reduced significantly in comparison to that of the original HY-2.6, e.g. Bronsted acidity decreased by ca. 69 folds by dealuminating HY-2.6 to HY-30. Catalytic results of Fischer esterification of methanol with carboxylic acids and aldol condensation of benzaldehyde with 1-heptanal have evidenced that the critical role of mesoporosity of the dealuminated Y zeolites in liquid-phase reactions. For example, in the esterification of lauric acid with methanol, HY-15 and HY-30 with hierarchical mesopores showed better catalytic activity (i.e. conversion of lauric acid: 7.9% and 24.5%, respectively) than HY-2.6 (4.0%). The analysis of the catalytic results along with the acidic property suggests that the acidity is less influential than the porosity of zeolite catalysts. Results from this study allow us to explain the origin of the high activity of zeolites with mesoporosity in the liquid-phase catalysis.

Furfural-Mediated Synthesis of Mesoporous Ti0.5Sn0.5O2 Solid-Solution Microspheres for Effective Photocatalytic Removal of As(III)

The development of a highly efficient photocatalyst for oxidizing and further removing toxic As(III) from the water environment remains a big challenge. Herein, mesoporous Ti0.5Sn0.5O2 (TSO-0.5) solid-solution microspheres are synthesized by a facile solvothermal method and followed by annealing. The mesoporous TSO-0.5 microspheres are systematically characterized in terms of the crystalline phases, morphological, optical, photoelectric, and photocatalytic properties using X-ray diffraction, scanning electron microscopy, N2 sorption–desorption, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, and electrochemical analysis. The characterizations show that TSO-0.5 is of well crystallinity, hierarchical mesoporosity, broad light responsive capacity, large surface area, and excellent photoelectric features. Under irradiation, the mesoporous TSO-0.5 microspheres exhibit ultrahigh photocatalytic activity for methyl orange (MO) degradation (0.537 min–1·m–2, ∼8 times that of TiO2) and As(...

Graphene-based “hybrid” aerogels with carbon nanotubes: Mesoporous network–functionality promoted defect density and electrochemical activity correlations

Electrochemical activity of graphene and graphene-based “hybrid” nanomaterials is crucial for energy and water sustainability applications, which requires fine tuning over combined geometric and electronic structures. We demonstrate that precise control of defects, porosity, and topological interconnectedness, invoked in hydrothermally synthesized graphene aerogel integrated with multi-walled carbon nanotubes, promotes finely tuned morphology, structure, defect number density, hierarchical mesoporosity, and conductivity and enhances the electrochemical heterogeneous electron transfer rate (kET). We prepared a range of graphene-based “hybrid” scaffolds (or monolithic aerogels) and their nitrogenated equivalents with varying graphene–carbon nanotube compositions using two synthetic schemes known as approaches 1 and 2. This study allows us to correlate quantitatively between number defect density (via Raman spectroscopy; RS) and heterogeneous electron transfer rate (via scanning electrochemical microscopy). RS provided microscale structural characterization revealing localized lattice vibrations. The first- and second-order Raman bands were analyzed in terms of band position, intensity ratio, and integrated intensity determining structural disorder, in-plane cluster size, inter-defect distance, and number defect density. The role of oxygenated (carbonyl; C═O, carboxyl; —COOH) and nitrogenated (pryridinic-N and graphitic/pyrrolic-N) functionalities and bonding configurations besides mesoporosity is emphasized for understanding the role of surface chemistry in regionally improved physicochemical (electroactivity and catalytic) properties. The defect-induced increase in finite electronic density of states (DOS) near Fermi level calculated using density functional theory under hydration helped in establishing moderate defect density for enhanced heterogeneous electron transfer rate as a critical onset such that the carbon system is electroactive while maintaining integral sp2 C structural network. Moreover, the defect sites allow sufficient overlap between DOS for graphene-based aerogels and redox probe wavefunctions, which emphasizes the experimental correlation establishments.

Hierarchically porous polymers containing triphenylamine for enhanced SF6 separation

Porous organic polymers (POPs) have a good potential for gas separation applications owing to their large surface area, structural robustness and chemical tunability. Previous studies have demonstrated the utility of POP-based adsorbents for carbon dioxide separation. However, no study has so far reported on the potential of POPs for capturing sulfur hexafluoride (SF6), which is an extremely potent greenhouse gas. Here we demonstrate that the amine-incorporated POPs synthesized through the co-condensation of dichloroxylene (DCX) and triphenylamine (TPA) for application in SF6/N2 separation. Large surface area and pore volume of DCX-based POPs provide the structural framework for high SF6 adsorption. The incorporation of tertiary amines favors the SF6/N2 selectivity without sacrificing the SF6 adsorption at the point of interest (0.1 bar) according to the combined evaluations of the ideal adsorbed solution theory and idealized vacuum swing adsorption. Further analysis revealed that the tertiary amines increase the isosteric heat of adsorption, a measure of affinity between adsorbate and adsorbent. Undertaking a comparative adsorption kinetics study, we also demonstrated that TPA-containing POPs exhibit much faster SF6 uptake than zeolite 13X, a commonly used commercial adsorbent, owing the co-existence of microporosity and mesoporosity that facilitates the diffusion of adsorbate within the adsorbent. Dynamic breakthrough and chromatographic measurements further confirmed the enhanced SF6 adsorption kinetics of TPA-containing POPs. In overall, we attributed the high SF6 separation performance of TPA-containing POPs to their two main characteristics: i) the presence of large micropores (c.a. 1.2 nm) alongside hierarchical mesoporosity, ii) the selectivity provided by amine functionalities.

Rapid synthesis of nanocrystalline zeolite W with hierarchical mesoporosity as an efficient solid basic catalyst for nitroaldol Henry reaction of vanillin with nitroethane

Rapid synthesis of nanocrystalline zeolite W with hierarchical mesoporosity as an efficient solid basic catalyst for nitroaldol Henry reaction of vanillin with nitroethane

Efficient N-doping of hollow core-mesoporous shelled carbon spheres via hydrothermal treatment in ammonia solution for the electrocatalytic oxygen reduction reaction

Nitrogen-doped hollow core-mesoporous shelled carbon spheres (NHMCSs) are successfully synthesized via a simple, scalable hydrothermal treatment of hollow mesoporous carbon spheres (HMCSs) with ammonia water as the nitrogen source. This strategy not only efficiently introduces nitrogen atoms into the carbon framework, but also causes the fracture of some spheres and increases the shell thickness of hollow spheres. The subsequent pyrolysis at 900 °C in Ar results in the transformation of pyrrolic-N to graphitic-N. The resulting NHMCS-900 has a high BET specific surface area (648 m2 g−1), large pore volume (1.06 cm3 g−1), hierarchical mesoporosity (2–8, 43.9 nm), uniform shells and large hollow cores. The electrochemical experiments indicate that NHMCS-900 as a metal-free electrocatalyst possesses the improved ORR activity with a close four-electron reaction pathway (∼3.88) and a peroxide yield lower than 10% over a wide potential range in alkaline solution. Contrary to commercial Pt/C, NHMCS-900 is unaffected by the methanol crossover effect and exhibits excellent long-term durability with 97.0% of the initial current density after 5.56 h of continuous operation. The excellent activity of NHMCS-900 is mainly attributed to the high relative content of pyridinic-N and graphitic-N. Besides, the superior activity is also ascribed to its unique structural properties, promoting fast and efficient mass transfer and providing inner and outer surfaces with N-relative active sites for ORR.

Generation of mesoporosity in MOR zeolites synthesized under perturbation conditions

The hydrothermal synthesis of various mesoporous materials with mordenite (MOR) structures is performed under perturbation conditions involving varying-temperature crystallizations and the use of ternary organic templates, and at least three types of mesoporous materials are obtained from the same starting gel containing the ternary organic templates. The greater structural diversities of these materials are found to correlate remarkably with the second-staged crystallization temperature and time. Among these materials, the two mesoporous materials crystallized incompletely over low temperature periods are differently structural composites consisting of MOR crystallites within disordered mesoporous phases, whereas the mesoporous mordenite crystallized completely over relatively high temperature period possesses the intrinsic microporosity and hierarchical mesoporosity. TEM morphological investigations on the mesoporous mordenite crystals demonstrate the formation of intracrystalline mesopores. Furthermore, an entirely new approach to synthesize mesoporous MOR zeolites is proposed based on the pore-inducing role of MOR structure defects and the adequate perturbation towards synthesis conditions.