Microporous Research Articles

From Waste to Worth: Innovative Pyrolysis of Textile Waste into Microporous Carbons for Enhanced Environmental Sustainability

The generation of synthetic textile waste is a growing global concern, with an unsustainable rate of expansion. This study addresses the growing issue of synthetic textile waste by converting polyester–polyurethane (PET-PU) post-industrial scraps into microporous carbon materials, which can be utilized for wastewater treatment. Using a straightforward pyrolysis process, we achieved a high specific surface area (632 m2/g) and narrow porosity range (2–10 Å) without requiring chemical activation. The produced carbon materials effectively adsorbed methylene blue and orange II dyes, with maximum adsorption capacities of 169.49 mg/g and 147.56 mg/g, respectively. Kinetic studies demonstrated that adsorption followed a pseudo-second-order model, indicating strong interactions between the adsorbent and dyes. Regeneration tests showed that the C-PET-PU could be reused for multiple cycles with over 85% retention of its original adsorption capacity. Preliminary life cycle assessment (LCA) and life cycle cost (LCC) analysis highlighted the environmental and economic advantages of this upcycling approach, showing a reduced global warming potential and a production cost of approximately 1.65 EUR/kg. These findings suggest that transforming PET-PU waste into valuable adsorbents provides a sustainable solution for the circular economy and highlights the potential for broader applications in environmental remediation.

Designing High Content Carbonylated β-Cyclodextrin/PBI Mixed Matrix Membrane as HT-PEM to Reduce H3PO4 Loss.

The high-temperature proton exchange membranes suffer from weak binding strength for phosphoric acid molecules, which seriously reduce the fuel cell efficiency, especially operation stability. Introduction of microporous material in the membrane can effectively reduce the leaching of phosphoric acid. However, due to the poor compatibility between the polymer and fillers, the membrane's performance significantly reduced at high fillers content. Therefore, in this work, the strategy of micropore confinement was developed; the β-cyclodextrin was carbonylated and introduced into PBI casting solution as solution state rather than dry powder for reducing the interface energy between two phases, thus further reducing interface defects and increasing the content of effective confined micropores within the membrane. By this way, carbonylated β-cyclodextrin/PBI (50 wt %) mixed matrix membranes were obtained, the proton conductivity reached 142 ± 4 mS cm-1, while the conductivity attenuation was only 16.6%.

Recent progress in the development of porous polymeric materials for oil ad/absorption application

Porous polymer materials, including polymer foams and melt-blown fibers, have nano or micro-size pores and a large specific surface area that endows them with great potential as engineered oil ad/absorption materials.

Energy-efficient nanobubble generation with microporous materials

Energy-efficient nanobubble generation with microporous materials

Tunable synthesis of heteroleptic zirconium-based porous coordination cages.

Zirconium-based porous coordination cages have been widely studied and have shown to be potentially useful for many applications as a result of their tunability and stability, likely as a result of their status as a molecular equivalent to the small 8 Å tetrahedral pores of UiO-66 (Zr6(μ3-O)4(μ2-OH)4(C8O4H4)6). Functional groups attached to these molecular materials endow them with a range of tunable properties. While so-called multivariate MOFs containing multiple types of functional groups on different bridging ligands within a structure are common, incorporating multiple functional moieties in permanently microporous molecular materials has proved challenging. By applying a mixed-ligand, or heteroleptic, synthesis strategy to cage formation, we have designed a straight-forward, one-pot synthesis of 10 Å zirconium-based molecular cages in a basket-shaped, or Zr12L6, geometry containing 3 : 3 ratios of combinations of two types of functional moieties from 11 different ligand options. Additionally, using more sterically hindered ligands, such as 5-benzyloxybenzene dicarboxylate, we show that ligand size governs the resulting cage geometry. This method allows for multiple functional groups to be incorporated in molecular cages and the ratio of moieties incorporated can be easily controlled. With this strategy in hand, we show that ligands for which zirconium cage syntheses have been elusive, such as 2,5-dihydroxybenzene dicarboxylate, have now been successfully incorporated into porous structures.

A new microporous organic-inorganic hybrid titanium phosphate for selective acetalization of glycerol.

We developed a novel strategy for synthesizing a highly acidic microporous hybrid titanium phosphate material (H-TiPOx) by incorporating 5-aminosalicylic acid (5-ASA) into the titanium phosphate framework. This new H-TiPOx serves as a Brønsted acid catalyst, exhibiting remarkable total surface acidity of 5.9 mmol g-1 and it efficiently catalyzes the acetalization of abundant biomass derived glycerol to solketal with over 99% selectivity.

A stable zeolite with atomically ordered and interconnected mesopore channel

Zeolites are crystalline microporous materials constructed by corner-sharing tetrahedra (SiO4 and AlO4), with many industrial applications as ion exchangers, adsorbents and heterogeneous catalysts1, 2, 3–4. However, the presence of micropores impedes the use of zeolites in areas dealing with bulky substrates. Introducing extrinsic mesopores, that is, intercrystal/intracrystal mesopores, in zeolites is a solution to overcome the diffusion barrier5, 6, 7–8. Still, those extrinsic mesopores are generally disordered and non-uniform; moreover, acidity and crystallinity are always, to some extent, impaired9. Thus, synthesizing thermally stable zeolites with intrinsic mesopores that are of uniform size and crystallographically connected with micropores, denoted here as intrinsic mesoporous zeolite, is highly desired but still not achieved. Here we report ZMQ-1 (Zeolitic Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, no. 1), an aluminosilicate zeolite with an intersecting intrinsic meso-microporous channel system delimited by 28 × 10 × 10-rings, in which the 28-ring has a free diameter of 22.76 Å × 11.83 Å, which reaches the mesopore domain. ZMQ-1 has high thermal and hydrothermal stability with tunable framework Si/Al molar ratios. ZMQ-1 is the first aluminosilicate zeolite with an intrinsic meso-microporous channel system. The Brønsted acidity of ZMQ-1 imparts high activity and unique selectivity in the catalytic cracking of heavy oil. The position of the organic structure-directing agent (OSDA) used for ZMQ-1 synthesis was determined from three-dimensional electron diffraction (3D ED) data, which shows the unique structure-directing role of the OSDA in the formation of the intrinsic meso-microporous zeolite. This provides an incentive for preparing other stable mesopore-containing zeolites.

Application of Ordered Porous Silica Materials in Drug Delivery: A Review.

Nanotechnology has significantly advanced various fields, including therapeutic delivery, through the use of nanomaterials as drug carriers. The biocompatibility of ordered porous silica materials makes them promising candidates for drug delivery systems, particularly in the treatment of cancer and other diseases. This review summarizes the use of microporous zeolites and mesoporous silica materials in drug delivery, focusing on their physicochemical properties and applications as drug carriers. Special emphasis is placed on strategies for encapsulation and functionalization, highlighting their role in enhancing drug loading and enabling targeted delivery. In conclusion, while ordered porous silica materials hold great potential for drug delivery systems, certain challenges remain.

Porous Materials for the Heterogeneously Catalyzed Synthesis of High Value-Added Products: Latest Trends and Future Prospects.

Heterogeneous catalysis currently stands as a foundational area in materials synthesis and applied chemistry. In this context, emphasizing the significance of heterogeneous catalysis in expediting chemical reactions and controlling the formation of desired products using porous materials represents an intriguing approach in the current technological landscape. This work delves into the synthesis and design of a variety of porous materials, encompassing microporous, mesoporous and macroporous materials (e. g. carbonaceous materials, metal oxides, MOFs, zeolites and functionalized analogues), alongside their properties and characteristics pivotal in heterogeneous catalysis. among others, and their subsequent modification, underscoring the significance of tailoring porous materials for specific catalytic applications.

Thermodynamics of Polyethylene Glycol Intrusion in Microporous Water.

Polymers can be used to augment the properties of microporous materials, affording enhanced processability, stability, and compatibility. Manipulating polymers to target specific properties, however, requires detailed knowledge of how different polymers and microporous materials interact. Here, we report a study of the thermodynamics of polyethylene glycol (PEG) intrusion into a representative hydrophobic zeolite (silicalite-1) and metal-organic framework [ZIF-67; Co(2-methylimidazolate)2] in water, both of which can be formed into colloidally stable aqueous dispersions─termed "microporous water"─with dry, guest-accessible pore networks. Through a combination of O2 capacity measurements and isothermal titration calorimetry (ITC), we establish relationships between PEG intrusion behavior, polymer length, polymer end groups, and the structure of the microporous framework. In particular, we find that PEG intrusion is exothermic for silicalite-1 but endothermic for ZIF-67. Our results provide fundamental insights into polymer intrusion in microporous materials that should inform efforts to design composite solids and fluids with enhanced functionality.

Design of a Noise Mitigation System Using Lightweight Graded Micro-Porous Material

Noise is a concern in industries like aviation. Existing acoustic materials have limitations in terms of effective broadband sound attenuation and operating conditions. This work addresses these limitations by designing and developing a noise mitigation system using lightweight graded micro-porous material made from Cenospheres and high-char binder. However, Cenospheres are nearly spherical with rough surfaces, so determining the flow properties of sound propagation is challenging, and direct measurements are expensive. We developed a multivariable-fit inverse method to estimate these properties using an experimental absorption coefficient, validated first with smooth-surface glass beads and then applied to micro-porous material. The determined flow properties were used in a predictive acoustic analysis and validated experimentally. It was demonstrated that a microstructurally graded material is needed to optimize both sound absorption and transmission loss. A graded material system designed for turbofan engine acoustic liners (50 mm thick) met the target broadband sound absorption coefficient of ≥0.50 and transmission loss of ≥20 dB above 500 Hz. The study also highlights that larger particles in thicker layers enhance sound absorption, while a graded micro-structure improves overall acoustic performance. This research offers a novel approach for designing a lightweight acoustic material for aviation, marking a breakthrough in passive noise mitigation technology.

Meso/Microporous Single‐Atom Catalysts Featuring Curved Fe−N4 Sites Boost the Oxygen Reduction Reaction Activity

AbstractZeolitic‐imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe−N/C materials, which are promising catalysts for enhancing the performance of Zn‐air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF‐derived Fe−N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe−N/C material with curved Fe−N4 active sites, denoted as FeSA−N/TC, through the pyrolysis of hemin‐modified ZIF films on ZnO nanorods, obtained from the self‐assembly reaction between Zn2+ from ZnO hydrolysis and 2‐methylimidazole. Density functional theory calculations demonstrate that the curved Fe−N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA−N/TC exhibits exceptional ORR performance with half‐wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA−N/TC achieves high peak power densities (H2−O2 PEMFC: 1100 mW cm−2; H2−Air PEMFC: 715 mW cm−2; liquid‐state ZAB: 228 mW cm−2; solid‐state ZAB: 112 mW cm−2), demonstrating its feasibility and efficiency in practical applications.

Mechanism of Electron-Beam-Induced Structural Degradation in ZIF-8 and its Electron Dose Tolerance.

Zeolitic-imidazolate frameworks (ZIFs) are crystalline microporous materials with promising potential for gas adsorption and catalysis application. Further research advances include studies on integrating ZIFs into nanodevice concepts. In detail for the application, e.g., electron-beam-assisted structural modifications or patterning, there is a need to understand potential structural degradation processes caused by such electron beams. Advanced transmission electron microscopy (TEM) has demonstrated its ability to study structures at the nanoscale. Here, we systematically investigated electron-beam-induced loss in crystallinity in ZIF-8 under various experimental conditions, using as measure the attenuation of the relative intensity and the relative displacement of electron diffraction Bragg planes with increasing cumulative electron dose. The {110} Bragg planes reflect the overall stability of the ZIF-8 unit-cell structure, while the {431} Bragg planes assess the stability of its micropore structure. We considered a relative loss of Bragg plane intensity of 37% as the threshold for determining the critical electron dose, which varied for different Bragg planes, with 35.6 ± 8.4 e-Å-2 for {110} and 11.4 ± 3.0 e-Å-2 for {431}. However, the critical dose per breakage of N-Zn bonds in a ZnN4 tetrahedra per different Bragg plane was found to be ∼3 e-Å-2, which indicates continuous, simultaneous breakage of N-Zn bonds throughout the crystal, confirming radiolysis as the dominant damage mechanism. In addition, we investigated the effects of TEM experiment parameters, including acceleration voltage, electron dose rate, cryogenic sample temperature, in situ sample drying, and change in conductivity of the sample substrate (e.g., graphene). Our results unravel the degradation mechanisms in ZIF-8 and provide threshold parameters for maximizing resolution in electron-beam-assisted experiments and processes.

Advances in Membranes from Microporous Materials for Hydrogen Separation from Light Gases

With the pressing concern of the climate change, hydrogen will undoubtedly play an essential role in the future to accelerate the way out from fossil fuel‐based economy. In this case, the role of membrane‐based separation cannot be neglected since, compared with other conventional process, membrane‐based process is more effective and consumes less energy. Regarding this, metal‐based membranes, particularly palladium, are usually employed for hydrogen separation because of its high selectivity. However, with the advancement of various microporous materials, the status quo of the metal‐based membranes could be challenged since, compared with the metal‐based membranes, they could offer better hydrogen separation performance and could also be cheaper to be produced. In this article, the advancement of membranes fabricated from five main microporous materials, namely silica‐based membranes, zeolite membranes, carbon‐based membranes, metal organic frameworks/covalent organic frameworks (MOF/COF) membranes and microporous polymeric membranes, for hydrogen separation from light gases are extensively discussed. Their performances are then summarized to give further insights regarding the pathway that should be taken to direct the research direction in the future.

Phase-transformable metal-organic polyhedra for membrane processing and switchable gas separation

The capability of materials to interconvert between different phases provides more possibilities for controlling materials’ properties without additional chemical modification. The study of state-changing microporous materials just emerged and mainly involves the liquefication or amorphization of solid adsorbents into liquid or glass phases by adding non-porous components or sacrificing their porosity. The material featuring reversible phases with maintained porosity is, however, still challenging. Here, we synthesize metal-organic polyhedra (MOPs) that interconvert between the liquid-glass-crystal phases. The modular synthetic approach is applied to integrate the core MOP cavity that provides permanent microporosity with tethered polymers that dictate the phase transition. We showcase the processability of this material by fabricating a gas separation membrane featuring tunable permeability and selectivity by switching the state. Compared to most conventional porous membranes, the liquid MOP membrane particularly shows the selectivity for CO2 over H2 with enhanced permeability.

Preparation and Antibacterial Properties of Poly (l-Lactic Acid)-Oriented Microporous Materials.

In this manuscript, an efficient self-reinforcing technology-solid hot drawing (SHD) technology-was combined with green processing supercritical carbon dioxide (SC-CO2) foaming technology to promote poly (l-lactic acid) (PLLA) to form an oriented micropore structure. In addition, Polydimethylsiloxane (PDMS), with a high affinity of CO2 and biological safety, was introduced to enhance the nucleation effect in SC-CO2 foaming and co-regulate the uniformity of oriented micropores' structure. The results showed that orientation induced PLLA crystallization, so the tensile strength was improved; the maximum tensile strength of the oriented micropores' PLLA reached 151.2 MPa. Furthermore, the micropores mainly improved the toughness; the maximum elongation at break reached 148.3%. It is worth mentioning that PDMS can form an antibacterial film on the surface of the material, so that the material has a continuous antibacterial effect.

Catalytic Pyrolysis of Polyethylene with Microporous and Mesoporous Materials: Assessing Performance and Mechanistic Understanding.

Testing the catalytic performance for the catalytic pyrolysis of plastic waste is hampered by mass transfer limitations induced by a size mismatch between the catalyst's pores and the bulky polymer molecules. To investigate this aspect, the catalytic behaviour of a series of microporous and mesoporous materials was assessed in the catalytic pyrolysis of polyethylene (PE). More specifically, a mesoporous material, namely sulfated zirconia (Zr(SO4)2) on SBA-15, was synthesized to increase the pore accessibility, which reduces mass transfer limitations and thereby enables to better assess the effect of active site density on catalyst activity. To demonstrate the potential of this approach, the mesoporous SBA-15 catalysts were compared to a series of microporous zeolite Y catalysts. Using the degradation temperature during thermogravimetric analysis (TGA) as a measure of activity, no correlation between acidity and activity was observed for microporous zeolite Y. However, depending on the Mw of PE, the reactivity of the mesoporous catalysts increased with increasing Zr(SO4)2 weight loading, showing that utilizing a mesoporous catalyst can overcome the accessibility limitations at least partially, which was further confirmed by polymer melt infiltration and in situ X-ray diffraction. Detailed product analysis revealed that more aromatics and coke deposits were produced with the more acidic zeolite Y materials. The mesoporous material remained active and structurally intact over multiple cycles and catalyses PE degradation via acid- and radical-based pathways.

Hierarchically Ordered Pore Engineering of Carbon Supports with High-Density Edge-Type Single-Atom Sites to Boost Electrochemical CO2 Reduction.

Metal sites at the edge of the carbon matrix possess unique geometric and electronic structures, exhibiting higher intrinsic activity than in-plane sites. However, creating single-atom catalysts with high-density edge sites remains challenging. Herein, the hierarchically ordered pore engineering of metal-organic framework-based materials to construct high-density edge-type single-atomic Ni sites for electrochemical CO2 reduction reaction (CO2RR) is reported. The created ordered macroporous structure can expose enriched edges, further increased by hollowing the pore walls, which overcomes the low edge percentage in the traditional microporous substrates. The prepared single-atomic Ni sites on the ordered macroporous carbon with ultra-thin hollow walls (Ni/H-OMC) exhibit Faraday efficiencies of CO above 90% in an ultra-wide potential window of 600mV and a turnover frequency of 3.4×104h-1, much superior than that of the microporous material with dominant plane-type sites. Theory calculations reveal that NiN4 sites at the edges have a significantly disrupted charge distribution, forming electron-rich Ni centers with enhanced adsorption ability with *COOH, thereby boosting CO2RR efficiency. Furthermore, a Zn-CO2 battery using the Ni/H-OMC cathode shows an unprecedentedly high power density of 15.9mW cm-2 and maintains an exceptionally stable charge-discharge performance over 100h.

Reversible Multi-Complexation of CO2 to Alkaline Earth Metal Ion-Pair at 400 ppm and 298 K.

The efficient capture of low-pressure CO2 remains a significant challenge due to the lack of established multi-complexation of CO2 to active sites in microporous materials. In this study, we introduce a novel concept of reversible multi-complexation of CO2 to alkaline earth metal (AEM) ion pairs, utilizing a host site in ferrierite-type zeolite (FER). This unique site constrains two AEM ions in proximity, thereby enhancing and isotopically spreading their electrostatic potentials within the zeolite cavity. This electrostatic potential-engineered micropore can trap up to four CO2 molecules, forming M2+-(CO2)n-M2+ (n=0-4, M=Ca, Sr, Ba) complexes, where each CO2 molecule is stabilized by interactions between terminal oxygen (Ot) in CO2 and the AEM ions. Notably, the Ba2+ pair site exhibits higher thermodynamic stability for multiple adsorptions due to the optimal binding mode of Ba2+-Ot-Ba2+. Through high-accuracy energy calculations, we have established the relationship among structure, CO2 uptake, and operating temperature/pressure, demonstrating that the Ba2+ pair site can capture four CO2 molecules even at concentrations as low as 400 ppm and at 298 K. Three of the four molecules of CO2 trapped were removable at room temperature and under vacuum. The findings in the present study provide a new direction for developing efficient CO2 adsorbents.

Reversible Multi‐Complexation of CO2 to Alkaline Earth Metal Ion‐Pair at 400 ppm and 298 K

AbstractThe efficient capture of low‐pressure CO2 remains a significant challenge due to the lack of established multi‐complexation of CO2 to active sites in microporous materials. In this study, we introduce a novel concept of reversible multi‐complexation of CO2 to alkaline earth metal (AEM) ion pairs, utilizing a host site in ferrierite‐type zeolite (FER). This unique site constrains two AEM ions in proximity, thereby enhancing and isotopically spreading their electrostatic potentials within the zeolite cavity. This electrostatic potential‐engineered micropore can trap up to four CO2 molecules, forming M2+−(CO2)n−M2+ (n=0–4, M=Ca, Sr, Ba) complexes, where each CO2 molecule is stabilized by interactions between terminal oxygen (Ot) in CO2 and the AEM ions. Notably, the Ba2+ pair site exhibits higher thermodynamic stability for multiple adsorptions due to the optimal binding mode of Ba2+−Ot−Ba2+. Through high‐accuracy energy calculations, we have established the relationship among structure, CO2 uptake, and operating temperature/pressure, demonstrating that the Ba2+ pair site can capture four CO2 molecules even at concentrations as low as 400 ppm and at 298 K. Three of the four molecules of CO2 trapped were removable at room temperature and under vacuum. The findings in the present study provide a new direction for developing efficient CO2 adsorbents.