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19 pages, 4615 KiB

Open AccessArticle

Ultrasound-Assisted Synthesis of Glycerol Carbonate Using Potassium-Modified Silicalite-1 as a Catalyst

by Jolanta Kowalska-Kuś, Ewa Janiszewska, Agnieszka Held, Aldona Jankowska, Anetta Hanć and Stanisław Kowalak

Molecules 2025, 30(7), 1590; https://doi.org/10.3390/molecules30071590 - 2 Apr 2025

Viewed by 267

Abstract

This study investigates the use of potassium-modified silicalite-1 as a catalyst for the transesterification of glycerol to glycerol carbonate (Glyc. Carbonate) with dimethyl carbonate (DMC). Silicalite-1, typically inactive due to the absence of extra-framework cations, was modified with potassium compounds (fluoride, chloride, and [...] Read more.

This study investigates the use of potassium-modified silicalite-1 as a catalyst for the transesterification of glycerol to glycerol carbonate (Glyc. Carbonate) with dimethyl carbonate (DMC). Silicalite-1, typically inactive due to the absence of extra-framework cations, was modified with potassium compounds (fluoride, chloride, and hydroxide), which create basic sites by interacting with structural defects formed through silicon removal. This modification significantly enhances the catalyst’s performance in glycerol transesterification. The reaction was conducted in both conventional batch reactor and ultrasound-assisted systems, including an ultrasonic bath and an ultrasonic probe, either within the bath or directly in the reactor. The direct ultrasound probe application yielded the most remarkable results, achieving a 96% Glyc. Carbonate yield at 70 °C in just 15 min—dramatically surpassing the batch reactor, which reached approximately 5%. These findings highlight the synergistic effect of potassium modification and ultrasound-assisted transesterification, offering a highly efficient and sustainable approach for glycerol valorization. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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18 pages, 1822 KiB

Open AccessArticle

Rational Design of Hierarchical Beta Zeolites via Post-Synthesis Treatments and Their Applications

by Michał Zieliński, Natalia Matysiak and Ewa Janiszewska

Molecules 2025, 30(5), 1030; https://doi.org/10.3390/molecules30051030 - 24 Feb 2025

Viewed by 452

Abstract

Hierarchical zeolites with micro- and mesoporous frameworks can overcome diffusional limitations of microporous systems. This study investigates the post-synthetic modification of Beta zeolite using different porogeneous agents (NaOH, NH₄OH, NH₄F) under identical conditions to compare their efficiency in generating [...] Read more.

Hierarchical zeolites with micro- and mesoporous frameworks can overcome diffusional limitations of microporous systems. This study investigates the post-synthetic modification of Beta zeolite using different porogeneous agents (NaOH, NH₄OH, NH₄F) under identical conditions to compare their efficiency in generating mesopores. The effect of treatment time was also examined for NH₄OH and NH₄F. The modified materials were characterized using physicochemical techniques and evaluated for catalytic performance in acetic acid esterification with alcohols of different sizes and adsorption of methylene blue. All the modifications increased mesoporosity but reduced acidity. NaOH produced the highest mesoporosity but significantly reduced acidity, while NH₄F retained the most acidity. Catalytic activity in esterification with methanol depended on acidity, but for larger alcohols (n-butanol, benzyl alcohol), activity was influenced by both acidity and mesoporosity. The NH₄OH- and NH₄F-modified materials, with lower mesoporosity but higher acidity, exhibited better performance with larger alcohols. In MB adsorption, the adsorption equilibrium rates increased with mesoporosity. The NaOH-modified sample reached equilibrium the fastest due to its superior mesoporosity, while the NH₄F-modified sample demonstrated the highest adsorption efficiency owing to its abundant Brønsted acid sites. These findings demonstrate that the choice of modifier affects mesoporosity, acidity, and functional performance, offering insights into tailoring hierarchical zeolites for specific applications. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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17 pages, 2986 KiB

Open AccessArticle

The Incorporation of Nanoconfined Poly(ionic liquid)s with Two-Dimensional Covalent Organic Frameworks to Enhance Proton Conduction

by Yonghong Wang, Xiaoxiao Liang, Ming Wang, Jiahui Wang, Yanan Gao and Fei Lu

Molecules 2025, 30(5), 1004; https://doi.org/10.3390/molecules30051004 - 21 Feb 2025

Viewed by 342

Abstract

Covalent organic frameworks (COFs) hold promising potential as high-temperature proton conductors due to their highly ordered nanostructures and high specific surface areas. However, due to their limited functional groups and poor membrane-engineering properties, finding practical applications for COF-based proton-conducting materials still remains challenging. [...] Read more.

Covalent organic frameworks (COFs) hold promising potential as high-temperature proton conductors due to their highly ordered nanostructures and high specific surface areas. However, due to their limited functional groups and poor membrane-engineering properties, finding practical applications for COF-based proton-conducting materials still remains challenging. Herein, we proposed a universal strategy to fabricate proton-conducting composite membranes by the incorporation of sulfonic acid-bearing COFs and zwitterionic poly(ionic liquid)s (PILs) via in situ polymerization. Zwitterionic PILs with methanesulfonate counter ions can work as the intrinsic proton sources, and the sulfonic acid groups on the COF nanochannels can act as the extrinsic proton suppliers. Benefiting from the spatial nanoconfinement of long-range ordered nanochannels and the enhanced electrostatic interactions with PILs, the COFs with high densities of sulfonic acid groups can endow the as-prepared composite membrane (PIL@TpBD(SO₃H)₂) with a comparable anhydrous proton conductivity of 3.20 × 10⁻³ S cm⁻¹ at 90 °C, which is much higher than that of conventional Nafion (~10⁻⁵ S cm⁻¹ at 90 °C under anhydrous condition). ¹H NMR DOSY spectra reveal that both the diffusion and dissociation of protons can be drastically facilitated upon nanoconfinement, demonstrating the promising efficiency of nanochannels in proton conduction. Moreover, the obtained composite membranes possess outstanding mechanical and thermal stability, which is crucial for their practical application. This study demonstrates proton conduction elevation in nanoconfined PILs and provides a promising insight into the engineering of stable COF-based proton-conducting materials. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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22 pages, 10352 KiB

Open AccessArticle

Physico-Chemical Properties of Granular Sorbents Based on Natural Bentonite Modified by Polyhydroxocations of Aluminum and Iron (III) by Co-Precipitation

by Bakytgul Kussainova, Gaukhar Tazhkenova, Ivan Kazarinov, Marina Burashnikova, Raigul Ramazanova, Yelena Ivashchenko, Bekzat Saurbayeva, Batima Tantybayeva, Ainur Seitkan, Gulsim Matniyazova, Khalipa Sadiyeva, Aisha Nurlybayeva and Aidana Bazarkhankyzy

Molecules 2025, 30(1), 195; https://doi.org/10.3390/molecules30010195 - 6 Jan 2025

Viewed by 856

Abstract

The physicochemical and adsorption properties of granular sorbents based on natural bentonite and modified sorbents based on it have been studied. It was found that modification of natural bentonite with iron (III) polyhydroxocations (mod. 1_Fe_5 GA) and aluminum (III) (mod. 1_Al_5 GA) by [...] Read more.

The physicochemical and adsorption properties of granular sorbents based on natural bentonite and modified sorbents based on it have been studied. It was found that modification of natural bentonite with iron (III) polyhydroxocations (mod. 1_Fe_5 GA) and aluminum (III) (mod. 1_Al_5 GA) by the “co-precipitation” method leads to a change in their chemical composition, structure, and sorption properties. It is shown that modified sorbents based on natural bentonite are finely porous (nanostructured) objects with a predominance of pores measuring 1.5–8.0 nm, with a specific surface area of 55–65 m²/g. Modification of bentonite with iron (III) and aluminum compounds by the “co-precipitation” method also leads to an increase in the sorption capacity of the obtained sorbents with respect to bichromate and arsenate anions and nickel cations by 5-10 times compared with natural bentonite. The obtained sorption isotherms were classified as Langmuir type isotherms. Kinetic analysis showed that at the initial stage the sorption process is controlled by an external diffusion factor, i.e. refers to the diffusion of sorbent from solution into a liquid film on the surface of the sorbent. Then the sorption process begins to proceed in a mixed diffusion mode, when it limits both the external diffusion factor and the internal diffusion factor (the diffusion of the sorbent to the active centers through the system of pores and capillaries). To determine the contribution of the chemical stage to the rate of adsorption of bichromate and arsenate anions and nickel(II) cations with the studied granular sorbents, kinetic curves were processed using the equations of chemical kinetics (pseudo-second-order model). As a result, it was found that the adsorption of the studied anions by modified sorbents based on natural bentonite is best described by a pseudo-second-order kinetic model. It is shown that the use of natural bentonite for the development of technology for the production of granular sorbents based on it has an undeniable advantage, firstly, in terms of its chemical and structural properties, it is easily and effectively modified, and secondly, having astringent properties, granules are easily made on its basis, which turn into ceramics during high-temperature firing. The result is a granular sorbent with high physical and mechanical properties. Since bentonite is an environmentally friendly product, the technology of recycling spent sorbents is also greatly simplified. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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18 pages, 5230 KiB

Open AccessArticle

Crosslinked Biodegradable Hybrid Hydrogels Based on Poly(ethylene glycol) and Gelatin for Drug Controlled Release

by Zhenzhen Zhao, Zihao Qin, Tianqing Zhao, Yuanyuan Li, Zhaosheng Hou, Hui Hu, Xiaofang Su and Yanan Gao

Molecules 2024, 29(20), 4952; https://doi.org/10.3390/molecules29204952 - 19 Oct 2024

Cited by 3 | Viewed by 1859

Abstract

A series of hybrid hydrogels of poly(ethylene glycol) (PEG) were synthesized using gelatin as a crosslinker and investigated for controlled delivery of the first-generation cephalosporin antibiotic, Cefazedone sodium (CFD). A commercially available 4-arm-PEG–OH was first modified to obtain four-arm-PEG–succinimidyl glutarate (4-arm-PEG–SG), which formed [...] Read more.

A series of hybrid hydrogels of poly(ethylene glycol) (PEG) were synthesized using gelatin as a crosslinker and investigated for controlled delivery of the first-generation cephalosporin antibiotic, Cefazedone sodium (CFD). A commercially available 4-arm-PEG–OH was first modified to obtain four-arm-PEG–succinimidyl glutarate (4-arm-PEG–SG), which formed the gelatin–PEG composite hydrogels (S_nN_m) through crosslinking with gelatin. To regulate the drug delivery, S_nN_m hydrogels with various solid contents and crosslinking degrees were prepared. The effect of solid contents and crosslinking degrees on the thermal, mechanical, swelling, degradation, and drug release properties of the hydrogels were intensively investigated. The results revealed that increasing the crosslinking degree and solid content of S_nN_m could not only enhance the thermal stability, swelling ratio (SR), and compression resistance capacity of S_nN_m but also prolong the degradation and drug release times. The release kinetics of the S_nN_m hydrogels were found to follow the first-order model, suggesting that the transport rate of CFD within the matrix of hydrogels is proportional to the concentration of the drug where it is located. Specifically, S₁N₁-III showed 90% mass loss after 60 h of degradation and a sustained release duration of 72 h. The cytotoxicity assay using the MTT method revealed that cell viability rates of S₁N₁ were higher than 95%, indicating excellent cytocompatibility. This study offers new insights and methodologies for the development of hydrogels as biomedical composite materials. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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14 pages, 7378 KiB

Open AccessArticle

Facile Fabrication of Co-Doped Porous Carbon from Coal Hydrogasification Semi-Coke for Efficient Microwave Absorption

by Yan-Fang Li, Li-Fang Wang, Shu-Juan Gao, Tan-Lai Yu, Qi-Feng Li and Jun-Wei Wang

Molecules 2024, 29(19), 4633; https://doi.org/10.3390/molecules29194633 - 29 Sep 2024

Viewed by 908

Abstract

A Co-doped porous carbon was successfully fabricated by a facile carbonizing procedure using coal hydrogasification semi-coke (SC) as the carbon and cobalt nitrate as the magnetic precursors, respectively. The mass ratio of the precursors was changed to regulate the microwave absorption (MA) capabilities. [...] Read more.

A Co-doped porous carbon was successfully fabricated by a facile carbonizing procedure using coal hydrogasification semi-coke (SC) as the carbon and cobalt nitrate as the magnetic precursors, respectively. The mass ratio of the precursors was changed to regulate the microwave absorption (MA) capabilities. The favorable MA capabilities are a result of a synergistic interaction be-tween the dielectric loss from the carbon framework, the magnetic loss from nano-sized Co particles, and multiple scattering from the residual pores. At a thickness of 4.0 mm, the Co/C composite showed the lowest reflection loss of −33.45 dB when the initial mass ratio of cobalt nitrate and SC was 1:1. The effective absorbing bandwidth (EAB) could achieve 3.5 GHz at 2 mm thickness. This work not only opens up a new avenue for the facile fabrication of dielectric and magnetic loss combinations and their structural design, but it also creates a new route for the high value-added exploitation of SC. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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11 pages, 2770 KiB

Open AccessArticle

Enhancement of Gaseous o-Xylene Elimination by Chlorosulfonic Acid-Modified H-Zeolite Socony Mobil-5

by Yaxu Wang, Xiaolong Ma, Hongmei Wang, Dandan Zhao, Yuheng Liu and Zichuan Ma

Molecules 2024, 29(15), 3507; https://doi.org/10.3390/molecules29153507 - 26 Jul 2024

Cited by 4 | Viewed by 1084

Abstract

It is important to develop effective strategies for enhancing the removal capacity of aromatic volatile organic compounds (VOCs) by modifying conventional porous adsorbents. In this study, a novel HZSM-5 zeolite-supported sulfonic acid (ZSM−OSO₃H) was prepared through ClSO₃H modification in [...] Read more.

It is important to develop effective strategies for enhancing the removal capacity of aromatic volatile organic compounds (VOCs) by modifying conventional porous adsorbents. In this study, a novel HZSM-5 zeolite-supported sulfonic acid (ZSM−OSO₃H) was prepared through ClSO₃H modification in dichloromethane and employed for the elimination of gaseous o-xylene. The ClSO₃H modification enables the bonding of −OSO₃H groups onto the HZSM-5 support, achieving a loading of 8.25 mmol·g⁻¹ and leading to a degradation in both crystallinity and textural structure. Within an active temperature range of 110–145 °C, ZSM−OSO₃H can efficiently remove o-xylene through a novel reactive adsorption mechanism, exhibiting a removal rate exceeding 98% and reaching a maximum breakthrough adsorption capacity of 264.7 mg. The adsorbed o-xylene derivative is identified as 3,4-dimethylbenzenesulfonic acid. ZSM−OSO₃H demonstrates superior adsorption performance for o-xylene along with excellent recyclability. These findings suggest that ClSO₃H sulfonation offers a promising approach for modifying various types of zeolites to enhance both the elimination and resource conversion of aromatic VOCs. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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18 pages, 5450 KiB

Open AccessArticle

Synthesis of Mesoporous Tetragonal ZrO₂, TiO₂ and Solid Solutions and Effect of Colloidal Silica on Porosity

by Linggen Kong, Inna Karatchevtseva, Tao Wei and Jessica Veliscek-Carolan

Molecules 2024, 29(14), 3278; https://doi.org/10.3390/molecules29143278 - 11 Jul 2024

Cited by 1 | Viewed by 1199

Abstract

Metal oxides possessing a large surface area, pore volume and desirable pore size provide more varieties and active industrial potentials. Nevertheless, it is very challenging to produce crystal metal oxides while keeping satisfactory porosity features, especially for ternary compositions. High temperature is usually [...] Read more.

Metal oxides possessing a large surface area, pore volume and desirable pore size provide more varieties and active industrial potentials. Nevertheless, it is very challenging to produce crystal metal oxides while keeping satisfactory porosity features, especially for ternary compositions. High temperature is usually needed to produce crystal metal oxides, which readily leads to the collapse of the pore structure. Herein, by employing a ‘soft’ dispersant agent and a hard silica template, ZrO₂, TiO₂ and Zr-Ti solid solutions having a tetragonal crystal structure are produced and the silica-leached materials are characterized from macroscopic to atomistic scales. The micron-sized particulate powders are composed of nanoscale ‘building blocks’, with crystallite sizes between ~8 and 21 nm. These polycrystalline ceramic powders exhibit a high specific surface area (up to ~200 m²·g⁻¹) and pore volume (up to 0.5 cm³·g⁻¹), with a pore size range of ~5–20 nm. Importantly, the Zr/Ti–O–Si–OH chemical bonds exist on the particle surface, with about two-thirds of the surface covered by silica. The hydroxyl groups can further post-graft organic ligands or directly associate with species. Synthesized mesoporous metal oxides are highly homogenous and could potentially be used in various applications because of their tetragonal structure and porosity features. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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14 pages, 5148 KiB

Open AccessArticle

An N-Rich Polymer for the Selective Recovery of Gold from Wastewater

by Haonan Dong, Ge Shang, Yi Zhang, Enrui Dai, Mingdong Shao, Chunfeng Chen, Hongxing He, Zhifeng Nie, Mingyang Xiong, Deren Miao and Sibiao Zhao

Molecules 2024, 29(10), 2398; https://doi.org/10.3390/molecules29102398 - 20 May 2024

Viewed by 1206

Abstract

The recovery of valuable gold from wastewater is of great interest because of the widespread use of the precious metal in various fields and the pollution generated by gold-containing wastes in water. In this paper, a water-insoluble cross-linked adsorbent material (TE) based on [...] Read more.

The recovery of valuable gold from wastewater is of great interest because of the widespread use of the precious metal in various fields and the pollution generated by gold-containing wastes in water. In this paper, a water-insoluble cross-linked adsorbent material (TE) based on cyanuric chloride (TCT) and ethylenediamine (EDA) was designed and used for the adsorption of Au(III) from wastewater. It was found that TE showed extremely high selectivity (D = 49,213.46) and adsorption capacity (256.19 mg/g) for Au(III) under acidic conditions. The adsorption rate remained above 90% eVen after five adsorption–desorption cycles. The adsorption process followed the pseudo-first-order kinetic model and the Freundlich isotherm model, suggesting that physical adsorption with a multilayer molecular overlay dominates. Meanwhile, the adsorption mechanism was obtained by DFT calculation and XPS analysis, and the adsorption mechanism was mainly the electrostatic interaction and electron transfer between the protonated N atoms in the adsorbent (TE) and AuCl₄⁻, which resulted in the redox reaction. The whole adsorption process was the result of the simultaneous action of physical and chemical adsorption. In conclusion, the adsorbent material TE shows great potential for gold adsorption and recovery. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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14 pages, 4755 KiB

Open AccessArticle

Highly Efficient Capture of Volatile Iodine by Conjugated Microporous Polymers Constructed Using Planar 3- and 4-Connected Organic Monomers

by Chaohui Li, Qianqian Yan, Huanjun Xu, Siyu Luo, Hui Hu, Shenglin Wang, Xiaofang Su, Songtao Xiao and Yanan Gao

Molecules 2024, 29(10), 2242; https://doi.org/10.3390/molecules29102242 - 10 May 2024

Cited by 4 | Viewed by 1580

Abstract

The effective capture and recovery of radioiodine species associated with nuclear fuel reprocessing is of significant importance in nuclear power plants. Porous materials have been proven to be one of the most effective adsorbents for the capture of radioiodine. In this work, we [...] Read more.

The effective capture and recovery of radioiodine species associated with nuclear fuel reprocessing is of significant importance in nuclear power plants. Porous materials have been proven to be one of the most effective adsorbents for the capture of radioiodine. In this work, we design and synthesize a series of conjugated microporous polymers (CMPs), namely, TPDA–TFPB CMP, TPDA–TATBA CMP, and TPDA–TECHO CMP, which are constructed based on a planar rectangular 4-connected organic monomer and three triangular 3-connected organic monomers, respectively. The resultant CMPs are characterized using various characterization techniques and used as effective adsorbents for iodine capture. Our experiments indicated that the CMPs exhibit excellent iodine adsorption capacities as high as 6.48, 6.25, and 6.37 g g⁻¹ at 348 K and ambient pressure. The adsorption mechanism was further investigated and the strong chemical adsorption between the iodine and the imine/tertiary ammonia of the CMPs, 3D network structure with accessible hierarchical pores, uniform micromorphology, wide π-conjugated structure, and high-density Lewis-base sites synergistically contribute to their excellent iodine adsorption performance. Moreover, the CMPs demonstrated good recyclability. This work provides guidance for the construction of novel iodine adsorbent materials with high efficiency in the nuclear power field. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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11 pages, 3513 KiB

Open AccessArticle

Mercury Adsorption and Oxidation Performance of an Iron-Based Oxygen Carrier during Coal Chemical Looping Process

by Guochao Hu, Shuju Zhao, Minggang Gao and Yongzhuo Liu

Molecules 2024, 29(10), 2195; https://doi.org/10.3390/molecules29102195 - 8 May 2024

Viewed by 909

Abstract

During chemical looping combustion (CLC) and chemical looping gasification (CLG) of coal, the release, migration, and speciation of mercury in coal are significantly influenced by oxygen-carrier materials; however, the underlying mechanism remains inadequately addressed. In this work, the effect of a typical iron-based [...] Read more.

During chemical looping combustion (CLC) and chemical looping gasification (CLG) of coal, the release, migration, and speciation of mercury in coal are significantly influenced by oxygen-carrier materials; however, the underlying mechanism remains inadequately addressed. In this work, the effect of a typical iron-based oxygen carrier on the release behavior of mercury from a bituminous coal and a lignite was investigated based on the Ontario-Hydro method. It is found that the effect of the iron-based oxygen carrier is attributed to three aspects: the enhanced release rate of mercury from coal, the adsorption of the released mercury, and the oxidization of gaseous Hg⁰ into Hg²⁺. With the increasing temperature, the adsorbance of mercury by the iron-based oxygen carrier decreases, while the oxidation of mercury enhances. Even at 900 °C, the adsorbance of mercury by the oxygen carrier remained at 0.1687 g/g, with a relative content of Hg²⁺ at 22.55%. Additionally, it was observed that iron-based oxygen carriers can physically absorb both Hg⁰ and Hg²⁺, while chemisorption refers to complex-compound formation between the iron-based oxygen carrier and mercury. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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22 pages, 2789 KiB

Open AccessArticle

About the Dominance of Mesopores in Physisorption in Amorphous Materials

by Christoph Strangfeld, Philipp Wiehle and Sarah Mandy Munsch

Molecules 2021, 26(23), 7190; https://doi.org/10.3390/molecules26237190 - 27 Nov 2021

Cited by 5 | Viewed by 2474

Abstract

Amorphous, porous materials represent by far the largest proportion of natural and men-made materials. Their pore networks consists of a wide range of pore sizes, including meso- and macropores. Within such a pore network, material moisture plays a crucial role in almost all [...] Read more.

Amorphous, porous materials represent by far the largest proportion of natural and men-made materials. Their pore networks consists of a wide range of pore sizes, including meso- and macropores. Within such a pore network, material moisture plays a crucial role in almost all transport processes. In the hygroscopic range, the pores are partially saturated and liquid water is only located at the pore fringe due to physisorption. Therefore, material parameters such as porosity or median pore diameter are inadequate to predict material moisture and moisture transport. To quantify the spatial distribution of material moisture, Hillerborg’s adsorption theory is used to predict the water layer thickness for different pore geometries. This is done for all pore sizes, including those in the lower nanometre range. Based on this approach, it is shown that the material moisture is almost completely located in mesopores, although the pore network is highly dominated by macropores. Thus, mesopores are mainly responsible for the moisture storage capacity, while macropores determine the moisture transport capacity, of an amorphous material. Finally, an electrical analogical circuit is used as a model to predict the diffusion coefficient based on the pore-size distribution, including physisorption. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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22 pages, 19639 KiB

Open AccessArticle

Mesoporous Poly(melamine-co-formaldehyde) Particles for Efficient and Selective Phosphate and Sulfate Removal

by Konstantin B. L. Borchert, Christine Steinbach, Berthold Reis, Niklas Gerlach, Philipp Zimmermann, Simona Schwarz and Dana Schwarz

Molecules 2021, 26(21), 6615; https://doi.org/10.3390/molecules26216615 - 31 Oct 2021

Cited by 10 | Viewed by 3106

Abstract

Due to the existence-threatening risk to aquatic life and entire ecosystems, the removal of oxyanions such as sulfate and phosphate from anthropogenic wastewaters, such as municipal effluents and acid mine drainage, is inevitable. Furthermore, phosphorus is an indispensable resource for worldwide plant fertilization, [...] Read more.

Due to the existence-threatening risk to aquatic life and entire ecosystems, the removal of oxyanions such as sulfate and phosphate from anthropogenic wastewaters, such as municipal effluents and acid mine drainage, is inevitable. Furthermore, phosphorus is an indispensable resource for worldwide plant fertilization, which cannot be replaced by any other substance. This raises phosphate to one of the most important mineral resources worldwide. Thus, efficient recovery of phosphate is essential for ecosystems and the economy. To face the harsh acidic conditions, such as for acid mine drainage, an adsorber material with a high chemical resistivity is beneficial. Poly(melamine-co-formaldehyde) (PMF) sustains these conditions whilst its very high amount of nitrogen functionalities (up to 53.7 wt.%) act as efficient adsorption sides. To increase adsorption capacities, PMF was synthesized in the form of mesoporous particles using a hard-templating approach yielding specific surface areas up to 409 m²/g. Different amounts of silica nanospheres were utilized as template and evaluated for the adsorption of sulfate and phosphate ions. The adsorption isotherms were validated by the Langmuir model. Due to their properties, the PMF particles possessed outperforming maximum adsorption capacities of 341 and 251 mg/g for phosphate and sulfate, respectively. Furthermore, selective adsorption of sulfate from mixed solutions of phosphate and sulfate was found for silica/PMF hybrid particles. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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16 pages, 7688 KiB

Open AccessArticle

Preparation and Electrical Properties of Polyacrylonitrile Based Porous Carbon by Different Activation Methods

by Xiaoqiang Wang, Yifan Tan, Meijiao Sun, Binbin Yu, Junhe Yang, Yuhua Xue and Guangzhi Yang

Molecules 2021, 26(12), 3499; https://doi.org/10.3390/molecules26123499 - 8 Jun 2021

Cited by 1 | Viewed by 2520

Abstract

Polyacrylonitrile (PAN)-based porous carbon was prepared by different methods of activation with PAN polymer microsphere as precursor. The morphology, structure and electrical properties for supercapacitor of the porous carbon were investigated. It was found that the morphology of PAN nanospheres tended to be [...] Read more.

Polyacrylonitrile (PAN)-based porous carbon was prepared by different methods of activation with PAN polymer microsphere as precursor. The morphology, structure and electrical properties for supercapacitor of the porous carbon were investigated. It was found that the morphology of PAN nanospheres tended to be destroyed in the process of one-step activation (activation and carbonization were carried out simultaneously, and could only be retained when the amount of activating agent KOH was small). While the spherical morphology could be well reserved during the two-step activation method (carbonization and activation sequentially). The specific surface area and pore volume increased first and then decreased, with the increase in activation holding time for both one-step and two-step activation methods. The specific surface area reached the maximum value with 2430 m² g⁻¹ for the one-step activation method and 2830 m² g⁻¹ for the two-step activation method. Additionally, their mass-specific capacitances were 178.8 F g⁻¹ and 160.2 F g⁻¹, respectively, under the current density of 1 A g⁻¹. After 2000 cycles, the specific capacitance retentions were 92.9% and 91.3%. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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Review

Jump to: Research

29 pages, 4766 KiB

Open AccessReview

Advancing Adsorption and Separation with Modified SBA-15: A Comprehensive Review and Future Perspectives

by Binjun Liang, Pingxin Zhu, Jihan Gu, Weiquan Yuan, Bin Xiao, Haixiang Hu and Mingjun Rao

Molecules 2024, 29(15), 3543; https://doi.org/10.3390/molecules29153543 - 27 Jul 2024

Cited by 7 | Viewed by 2802

Abstract

Mesoporous silica SBA-15 has emerged as a promising adsorbent and separation material due to its unique structural and physicochemical properties. To further enhance its performance, various surface modification strategies, including metal oxide and noble metal incorporation for improved catalytic activity and stability, organic [...] Read more.

Mesoporous silica SBA-15 has emerged as a promising adsorbent and separation material due to its unique structural and physicochemical properties. To further enhance its performance, various surface modification strategies, including metal oxide and noble metal incorporation for improved catalytic activity and stability, organic functionalization with amino and thiol groups for enhanced adsorption capacity and selectivity, and inorganic–organic composite modification for synergistic effects, have been extensively explored. This review provides a comprehensive overview of the recent advances in the surface modification of SBA-15 for adsorption and separation applications. The synthesis methods, structural properties, and advantages of SBA-15 are discussed, followed by a detailed analysis of the different modification strategies and their structure–performance relationships. The adsorption and separation performance of functionalized SBA-15 materials in the removal of organic pollutants, heavy metal ions, gases, and biomolecules, as well as in chromatographic and solid–liquid separation, is critically evaluated. Despite the significant progress, challenges and opportunities for future research are identified, including the development of low-cost and sustainable synthesis routes, rational design of SBA-15-based materials with tailored properties, and integration into practical applications. This review aims to guide future research efforts in developing advanced SBA-15-based materials for sustainable environmental and industrial applications, with an emphasis on green and scalable modification strategies. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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21 pages, 3532 KiB

Open AccessFeature PaperReview

Encapsulation in Alginates Hydrogels and Controlled Release: An Overview

by Camille Colin, Emma Akpo, Aurélie Perrin, David Cornu and Julien Cambedouzou

Molecules 2024, 29(11), 2515; https://doi.org/10.3390/molecules29112515 - 26 May 2024

Cited by 8 | Viewed by 4494

Abstract

This review aims to gather the current state of the art on the encapsulation methods using alginate as the main polymeric material in order to produce hydrogels ranging from the microscopic to macroscopic sizes. The use of alginates as an encapsulation material is [...] Read more.

This review aims to gather the current state of the art on the encapsulation methods using alginate as the main polymeric material in order to produce hydrogels ranging from the microscopic to macroscopic sizes. The use of alginates as an encapsulation material is of growing interest, as it is fully bio-based, bio-compatible and bio-degradable. The field of application of alginate encapsulation is also extremely broad, and there is no doubt it will become even broader in the near future considering the societal demand for sustainable materials in technological applications. In this review, alginate’s main properties and gelification mechanisms, as well as some factors influencing this mechanism, such as the nature of the reticulation cations, are first investigated. Then, the capacity of alginate gels to release matter in a controlled way, from small molecules to micrometric compounds, is reported and discussed. The existing techniques used to produce alginates beads, from the laboratory scale to the industrial one, are further described, with a consideration of the pros and cons with each techniques. Finally, two examples of applications of alginate materials are highlighted as representative case studies. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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30 pages, 5244 KiB

Open AccessReview

Development of Starch-Based Materials Using Current Modification Techniques and Their Applications: A Review

by Sumedha M. Amaraweera, Chamila Gunathilake, Oneesha H. P. Gunawardene, Nimasha M. L. Fernando, Drashana B. Wanninayaka, Rohan S. Dassanayake, Suranga M. Rajapaksha, Asanga Manamperi, Chakrawarthige A. N. Fernando, Asela K. Kulatunga and Aruna Manipura

Molecules 2021, 26(22), 6880; https://doi.org/10.3390/molecules26226880 - 15 Nov 2021

Cited by 79 | Viewed by 14607

Abstract

Starch is one of the most common biodegradable polymers found in nature, and it is widely utilized in the food and beverage, bioplastic industry, paper industry, textile, and biofuel industries. Starch has received significant attention due to its environmental benignity, easy fabrication, relative [...] Read more.

Starch is one of the most common biodegradable polymers found in nature, and it is widely utilized in the food and beverage, bioplastic industry, paper industry, textile, and biofuel industries. Starch has received significant attention due to its environmental benignity, easy fabrication, relative abundance, non-toxicity, and biodegradability. However, native starch cannot be directly used due to its poor thermo-mechanical properties and higher water absorptivity. Therefore, native starch needs to be modified before its use. Major starch modification techniques include genetic, enzymatic, physical, and chemical. Among those, chemical modification techniques are widely employed in industries. This review presents comprehensive coverage of chemical starch modification techniques and genetic, enzymatic, and physical methods developed over the past few years. In addition, the current applications of chemically modified starch in the fields of packaging, adhesives, pharmaceuticals, agriculture, superabsorbent and wastewater treatment have also been discussed. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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26 pages, 718 KiB

Open AccessReview

Research Progress and Application of Single-Atom Catalysts: A Review

by He He, Hudson Haocheng Wang, Junjian Liu, Xujun Liu, Weizun Li and Yannan Wang

Molecules 2021, 26(21), 6501; https://doi.org/10.3390/molecules26216501 - 28 Oct 2021

Cited by 54 | Viewed by 12978

Abstract

Due to excellent performance properties such as strong activity and high selectivity, single-atom catalysts have been widely used in various catalytic reactions. Exploring the application of single-atom catalysts and elucidating their reaction mechanism has become a hot area of research. This article first [...] Read more.

Due to excellent performance properties such as strong activity and high selectivity, single-atom catalysts have been widely used in various catalytic reactions. Exploring the application of single-atom catalysts and elucidating their reaction mechanism has become a hot area of research. This article first introduces the structure and characteristics of single-atom catalysts, and then reviews recent preparation methods, characterization techniques, and applications of single-atom catalysts, including their application potential in electrochemistry and photocatalytic reactions. Finally, application prospects and future development directions of single-atom catalysts are outlined. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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29 pages, 4721 KiB

Open AccessReview

Ceramic-Polymer Composite Membranes for Water and Wastewater Treatment: Bridging the Big Gap between Ceramics and Polymers

by Masashi Kotobuki, Qilin Gu, Lei Zhang and John Wang

Molecules 2021, 26(11), 3331; https://doi.org/10.3390/molecules26113331 - 1 Jun 2021

Cited by 38 | Viewed by 8367

Abstract

Clean water supply is an essential element for the entire sustainable human society, and the economic and technology development. Membrane filtration for water and wastewater treatments is the premier choice due to its high energy efficiency and effectiveness, where the separation is performed [...] Read more.

Clean water supply is an essential element for the entire sustainable human society, and the economic and technology development. Membrane filtration for water and wastewater treatments is the premier choice due to its high energy efficiency and effectiveness, where the separation is performed by passing water molecules through purposely tuned pores of membranes selectively without phase change and additional chemicals. Ceramics and polymers are two main candidate materials for membranes, where the majority has been made of polymeric materials, due to the low cost, easy processing, and tunability in pore configurations. In contrast, ceramic membranes have much better performance, extra-long service life, mechanical robustness, and high thermal and chemical stabilities, and they have also been applied in gas, petrochemical, food-beverage, and pharmaceutical industries, where most of polymeric membranes cannot perform properly. However, one of the main drawbacks of ceramic membranes is the high manufacturing cost, which is about three to five times higher than that of common polymeric types. To fill the large gap between the competing ceramic and polymeric membranes, one apparent solution is to develop a ceramic-polymer composite type. Indeed, the properly engineered ceramic-polymer composite membranes are able to integrate the advantages of both ceramic and polymeric materials together, providing improvement in membrane performance for efficient separation, raised life span and additional functionalities. In this overview, we first thoroughly examine three types of ceramic-polymer composite membranes, (i) ceramics in polymer membranes (nanocomposite membranes), (ii) thin film nanocomposite (TFN) membranes, and (iii) ceramic-supported polymer membranes. In the past decade, great progress has been made in improving the compatibility between ceramics and polymers, while the synergy between them has been among the main pursuits, especially in the development of the high performing nanocomposite membranes for water and wastewater treatment at lowered manufacturing cost. By looking into strategies to improve the compatibility among ceramic and polymeric components, we will conclude with briefing on the perspectives and challenges for the future development of the composite membranes. Full article

(This article belongs to the Special Issue Recent Advances in Porous Materials)

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