| 1. |
- Kong, Xueying, 1993-
(författare)
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Porous Materials and Their Cellulose-Based Composites : Synthesis, Nanoengineering, and Applications
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Porous materials, such as porous carbons (PCs), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), show considerable potential across various fields because of their rich microporous and mesoporous structures and large surface areas, yet they grapple with challenges like environmentally unfriendly fabrication methods and poor processability. In this thesis, we investigated environmentally friendly fabrication methods for porous materials, nanoengineering techniques for processing these materials, and their potential applications.Cladophora cellulose (CC), a naturally abundant biopolymer, was used to prepare PC via a one-step physical carbonization/activation method without using any corrosive activation agents. The obtained CC-derived PC (CPC) showed a high specific surface area (507.2 m2 g−1) and rich microporous structure. Additionally, we introduced a simple and environmentally friendly method for synthesizing imine-linked COFs at room temperature using water as the solvent. The method involves a key step in which aldehyde monomers are pre-activated by acetic acid, which promotes the aldehyde monomers to dissolve in water, enhancing their reactivity with amine monomers, and ensuring the formation of crystalline COFs. Consequently, we synthesized 16 distinct imine-linked COFs with high crystallinity and specific surface areas. Furthermore, this thesis focusses on improving the poor processability of these materials caused by the infusible and insoluble nature of their powders. The poor processability of these porous materials makes them difficult to process into desired structures and shapes. Here, we introduce two nanoengineering methods: i) Interweaving porous materials with CC nanofibers (CNFs) to form CNF-porous material aqueous solutions; and ii) Interfacial synthesis of porous materials on the surface of carboxylated CNFs to form CNF@porous materials with nanofiber structures in aqueous solutions. The obtained composite suspensions can be fabricated into freestanding and flexible composite nanopapers via a vacuum filtration and drying process. In addition, they can be processed into freestanding aerogels through a freeze-drying process. Consequently, we have successfully prepared freestanding and flexible CC-CPC nanopapers and CC-CPC aerogels, c-CNT@COF/CNT/CNF nanopapers (c-CNT: carboxylated carbon nanotube), CNF@MOF nanopapers, and CNF@COF nanopapers and demonstrated their potential in various applications, from efficient CO2 capture and organic pollutant removal to advanced energy storage and solar vapor generation. In summary, we used environmentally friendly methods to synthesize PC and imine-linked COFs, circumventing the need for corrosive chemical agents and toxic organic solvents, respectively. Furthermore, by combining CNFs with porous materials, we successfully created freestanding and flexible nanopapers and aerogels, thereby addressing the issue of poor processability associated with porous materials.
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| 2. |
- Luo, Dan, et al.
(författare)
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Green, General and Low-cost Synthesis of Porous Organic Polymers in Sub-kilogram Scale for Catalysis and CO2 Capture
- 2023
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Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. ; n/a:n/a
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Tidskriftsartikel (refereegranskat)abstract
- Porous organic polymers (POPs) with high porosity and tunable functionalities have been widely studied for use in gas separation, catalysis, energy conversion and energy storage. However, the high cost of organic monomers, and the use of toxic solvents and high temperatures during synthesis pose obstacles for large-scale production. Herein, we report the synthesis of imine and aminal-linked POPs using inexpensive diamine and dialdehyde monomer in green solvents. Theoretical calculations and control experiments show that using meta-diamines is crucial for forming aminal linkages and branching porous networks from [2 + 2] polycondensation reactions. The method demonstrates good generality in that 6 POPs were successfully synthesized from different monomers. Additionally, we scaled up the synthesis in ethanol at room temperature, resulting in the production of POPs in sub-kilogram quantities at a relatively low cost. Proof-of-concept studies demonstrate that the POPs can be used as high-performance sorbents for CO2 separation and as porous substrates for efficient heterogeneous catalysis. This method provides an environmentally friendly and cost-effective approach for large-scale synthesis of various POPs.
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| 3. |
- Xu, Qinqin, et al.
(författare)
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Gold recovery from E-waste using freestanding nanopapers of cellulose and ionic covalent organic frameworks
- 2023
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Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 458, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- The ever-increasing production of electronic devices generates a huge amount of electronic waste (E-waste). Therefore, there is an urgent need for advanced recycling technology for E-waste that provides both economic and environmental benefits. Herein, we describe the preparation of flexible, freestanding CF-COF nanopapers consisting of cellulose fibers (CFs) and guanidinium-based ionic covalent organic framework (COF) that can be used for recovering gold from E-waste leaching solutions via a membrane separation technique. Due to the synergetic effects of physical adsorption, ion exchange and chemical reduction, the COF has an extremely high capture capacity (up to 1,794 mg of Au per gram of COF), is highly selective and has fast kinetics for adsorbing trace amounts of [AuCl4]− in aqueous solution. The high COF loadings (∌50 wt%) and hierarchical porosity of the CF-COF nanopapers resulted in excellent performance when capturing gold species from the E-waste leaching solution. This study provides new possibilities for developing sustainable membrane materials, and highly efficient and cost-effective techniques for the recovery of precious metals from E-waste.
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| 4. |
- Du, Xing-Hao, et al.
(författare)
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BODIPY-linked conjugated porous polymers for dye wastewater treatment
- 2022
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 332
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Tidskriftsartikel (refereegranskat)abstract
- As a new family of functional porous materials, conjugated porous polymers (CPPs) with tuneable porosities and molecular architectures show great potentials in adsorption, light harvesting, and catalysis applications. This paper describes the incorporation of strong visible-light absorbing BODIPY molecules into the skeleton of CPPs via Sonogashira coupling reactions. The obtained CPPs displayed integrated properties of high surface area, hierarchical porous structures and strong visible-light absorption. As a result, the CPPs showed relatively high adsorption capacity and high photocatalytic degradation efficiency towards organic dyes. Mechanism studies revealed that the CPPs enabled the generation of singlet oxygen species under light irradiation, accounting for the main driving force for the dye degradation. This study provides a new route for the development of organic adsorbents and photocatalysts for water treatment and purification.
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| 5. |
- Hu, Lei, et al.
(författare)
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Molecular surface modification of silver chalcogenolate clusters
- 2022
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Ingår i: Dalton Trans.. - : Royal Society of Chemistry (RSC). ; 51, s. 3241-3247
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a molecular surface modification approach to synthesizing a family of silver chalcogenolate clusters (SCCs) containing the same [Ag12S6] core and different surface-bonded organic ligands (DMAc or pyridines; DMAc = dimethylacetamide), with the aim of tuning the luminescence property and increasing the structural stability of the SCCs. The SCCs displayed strong and tuneable luminescence emissions at 77 K (from green to orange to red) as influenced by the peripheral pyridine ligands. In addition, SCC 5 protected by pyridine molecules was stable in ambient air, humid air and even liquid water for a long time (up to 1 week), and it was more structurally stable than SCC 1 bonded with DMAc molecules under the same conditions. The high structural stability of SCC 5 can be explained by the ability of pyridine molecules to form strong coordination bonds with silver atoms. This study offers a new way of designing structurally stable metal nanoclusters with tuneable physicochemical properties.
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| 6. |
- Kong, Xueying, et al.
(författare)
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All-cellulose-based freestanding porous carbon nanocomposites and their versatile applications
- 2022
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Ingår i: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 232
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Tidskriftsartikel (refereegranskat)abstract
- Porous carbons are key functional materials in a range of industrial processes such as gas adsorption and separation, water treatment, and energy conversion and storage. It is, however, important from a sustainability perspective for porous carbons to be synthesized from naturally abundant biopolymers. Nanoengineering of porous carbons using facile binder-free techniques presents significant challenges, but is deemed beneficial for broadening their field of use and improving their application performance. This paper discusses the processing of cellulose-based porous carbons interwoven with cellulose nanofibers to fabricate freestanding nanopapers and aerogels, aiming at developing processable, fully sustainable, and all-cellulose-based carbon nanocomposites. The aerogels, which have cellular networks, low density and high mechanical strength, were investigated as sorbents for CO2 capture and removal of various organics. The presence of rich ultramicropores allows the aerogels to adsorb relatively high amounts of CO2, with high selectivity of CO2-over-N-2 (up to 111). More importantly, the sorbents have high CO2 working capacities and excellent recyclability under temperature swing adsorption conditions. In addition, the aerogels can adsorb various organic solvents remarkably well, corresponding to 100-217 times their own weight. The nanopapers are active photothermal materials that can be applied as solar absorbers for interfacial solar vapor generation, providing a high evaporation rate (1.74 kg m(-2) h(-1) under one sun illumination). The nanopapers were also employed as electrodes in flexible, foldable super capacitors with high areal capacitances. This study may provide a basis for further development of and new application areas for all-cellulose-based nanocomposites.
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| 7. |
- Kong, Xueying, et al.
(författare)
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Ambient Aqueous Synthesis of Imine-Linked Covalent Organic Frameworks (COFs) and Fabrication of Freestanding Cellulose Nanofiber@COF Nanopapers
- 2023
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 146:1, s. 742-751
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Tidskriftsartikel (refereegranskat)abstract
- Covalent organic frameworks (COFs) are usually synthesized under solvothermal conditions that require the use of toxic organic solvents, high reaction temperatures, and complicated procedures. Additionally, their insolubility and infusibility present substantial challenges in the processing of COFs. Herein, we report a facile, green approach for the synthesis of imine-linked COFs in an aqueous solution at room temperature. The key behind the synthesis is the regulation of the reaction rate. The preactivation of aldehyde monomers using acetic acid significantly enhances their reactivity in aqueous solutions. Meanwhile, the still somewhat lower imine formation rate and higher imine breaking rates in aqueous solution, in contrast to conventional solvothermal synthesis, allow for the modulation of the reaction equilibrium and the crystallization of the products. As a result, highly crystalline COFs with large surface areas can be formed in relatively high yields in a few minutes. In total, 16 COFs are successfully synthesized from monomers with different molecular sizes, geometries, pendant groups, and core structures, demonstrating the versatility of this approach. Notably, this method works well on the gram scale synthesis of COFs. Furthermore, the aqueous synthesis facilitates the interfacial growth of COF nanolayers on the surface of cellulose nanofibers (CNFs). The resulting CNF@COF hybrid nanofibers can be easily processed into freestanding nanopapers, demonstrating high efficiency in removing trace amounts of antibiotics from wastewater. This study provides a route to the green synthesis and processing of various COFs, paving the way for practical applications in diverse fields.
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| 8. |
- Kong, Xueying, et al.
(författare)
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Aqueous synthesis and engineering of imine-linked covalent organic frameworks
- 2023
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Ingår i: One-day symposium: Sorption, Transport and Catalysis in Metal-Organic Frameworks. Uppsala 18/9 2023. - Uppsala.
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Konferensbidrag (refereegranskat)abstract
- Covalent organic frameworks (COFs) are typically synthesized through solvothermal methods, which necessitate the use of hazardous organic solvents, elevated reaction temperatures, and intricate procedures. Additionally, their insolubility and inability to melt present substantial challenges in the processing of COFs. In this study, we present an eco-friendly method for synthesizing imine-linked COFs by simply stirring the initial materials in an aqueous solution at room temperature. A key element of this approach involves the pre-activation of aldehyde monomers using acetic acid, significantly enhancing their reactivity in aqueous solutions. This innovative strategy results in the rapid formation of highly crystalline COFs formed at relatively high yields, with substantial surface areas, within minutes. Remarkably, this method performs exceptionally well on a gram-scale, producing highly crystalline and porous COFs in scaled-up reactions.We successfully synthesized a total of 15 COFs using monomers with diverse molecular sizes, geometries, pendant groups, and core structures, underscoring the versatility of this approach. Furthermore, our use of cellulose nanofibers (CNFs) as a substrate during the syntheses allows for the growth of COF nanolayers on the CNF surface. These CNF@COF hybrid nanofibers can be effortlessly transformed into freestanding nanopapers.Significantly, both COF powders and CNF@COF nanopapers exhibit remarkable efficiency in removing trace amounts of antibiotics from wastewater. This research offers a promising avenue for the green synthesis and processing of various COFs, paving the way for practical applications in diverse fields.
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| 9. |
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| 10. |
- Shi, Tianhui, et al.
(författare)
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Postsynthetic amine modification of porous organic polymers for CO2 capture and separation
- 2023
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Ingår i: Journal of Polymer Science. ; n/a:n/a
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Porous organic polymers (POPs) constitute an important class of sorbents studied in various adsorption and separation processes. Their unique properties, including high surface areas, adjustable pore sizes, and surface chemistries make them ideal candidates for CO2 capture. To achieve a high CO2 adsorption capacity and selectivity, particularly at the low partition pressures required for post-combustion CO2 capture or direct capture of CO2 from the atmosphere, incorporating amines onto the polymer frameworks or within the pores has shown much promise. This review provides a comprehensive summary of recent studies on the synthesis and CO2 capture performance of amine-functionalized POPs. The review also provides a detailed discussion of structure-performance relationships, focusing on how the loading amount and amine type influence CO2 capture capacity, CO2/N2 selectivity, heat of adsorption, sorption kinetics, and recyclability of POPs. Additionally, the authors offer their perspective on the challenges associated with the practical implementation of amine-modified POPs for CO2 capture.
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