R-3 Repository :: Browsing by Author "Zhu, Dongyang"

Browsing by Author "Zhu, Dongyang"

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3D Covalent Organic Frameworks with Interpenetrated pcb Topology Based on 8-Connected Cubic Nodes
(American Chemical Society, 2022) Shan, Zhen; Wu, Miaomiao; Zhu, Dongyang; Wu, Xiaowei; Zhang, Kan; Verduzco, Rafael; Zhang, Gen
The connectivity of building units for 3D covalent organic frameworks (COFs) has long been primarily 4 and 6, which have severely curtailed the structural diversity of 3D COFs. Here we demonstrate the successful design and synthesis of a porphyrin based, 8-connected building block with cubic configuration, which could be further reticulated into an unprecedented interpenetrated pcb topology by imine condensation with linear amine monomers. This study presents the first case of high-connectivity building units bearing 8-connected cubic nodes, thus greatly enriching the topological possibilities of 3D COFs.
Metal Oxide Catalysts for the Synthesis of Covalent Organic Frameworks and One-Step Preparation of Covalent Organic Framework-Based Composites
(American Chemical Society, 2021) Zhu, Yifan; Zhu, Dongyang; Yan, Qianqian; Gao, Guanhui; Xu, Jianan; Liu, Yifeng; Alahakoon, Sampath B.; Rahman, Muhammad M.; Ajayan, Pulickel M.; Egap, Eilaf; Verduzco, Rafael; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
The integration of covalent organic frameworks (COFs) with inorganic materials provides opportunities to develop a new class of composite materials with high surface areas and novel functionalities relevant to photocatalysis, chemical adsorption, and magnetic resonance imaging. However, current methods for the preparation of COF-based composites require challenging, multistep synthetic protocols. Herein, we report a one-pot synthesis approach using a wide range of metal oxides to catalyze the synthesis of highly crystalline and porous COFs. We found that a large variety of metal oxides served as effective catalysts for the synthesis of imine COFs, including niobium(V) oxide (Nb2O5), nickel(II) oxide (NiO), manganese(IV) dioxide (MnO2), ruthenium(IV) oxide (RuO2), zinc(II) oxide (ZnO), lead(II) oxide (PbO), tellurium(IV) dioxide (TeO2), tin(IV) oxide (SnO2), manganese(III) oxide (Mn2O3), zirconium(IV) dioxide (ZrO2), and aluminum(III) oxide (Al2O3). Nb2O5 was effective for the synthesis of a wide range of COFs with different functional groups and pore sizes, and these reactions produced a metal oxide/COF composite. By using Fe3O4 nanoparticles (NPs) as the catalyst, we produced COF-based nanocomposites with Fe3O4 NPs distributed throughout the final COF product. The Fe3O4/COF nanocomposite had a high surface area of 2196 m2 g–1. This work demonstrates a class of novel, low-cost catalysts for synthesizing COFs and a new approach to produce metal oxide/COF composite materials.
Patterning, Transfer, and Tensile Testing of Covalent Organic Framework Films with Nanoscale Thickness
(American Chemical Society, 2021) Zhu, Dongyang; Hu, Zhiqi; Rogers, Tanya K.; Barnes, Morgan; Tseng, Chia-Ping; Mei, Hao; Sassi, Lucas M.; Zhang, Zhuqing; Rahman, Muhammad M.; Ajayan, Pulickel M.; Verduzco, Rafael
Covalent organic frameworks (COFs) are promising materials for a variety of applications, including membrane-based separations, thin-film electronics, and as separators for electrochemical devices. Robust mechanical properties are critical to these applications, but there are no reliable methods for patterning COFs or producing free-standing thin films for direct mechanical testing. Mechanical testing of COFs has only been performed on films supported by a rigid substrate. Here, we present a method for patterning, transferring, and measuring the tensile properties of free-floating nanoscale COF films. We synthesized COF powders by condensation of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehyde (PDA) and prepared uniform thin films by spin casting from a mixture of trifluoroacetic acid and water. The COF films were then reactivated to recover crystallinity and patterned by plasma etching through a poly(dimethylsiloxane) (PDMS) mask. The films were transferred to the surface of water, and we performed direct tensile tests. We measured a modulus of approximately 1.4 GPa for TAPB-PDA COF and a fracture strain of 2.5%, which is promising for many applications. This work advances the development of COFs for thin-film applications by demonstrating a simple and generally applicable approach to cast, pattern, and transfer COF thin films and to perform direct mechanical analysis.
Porphyrin-based donor–acceptor COFs as efficient and reusable photocatalysts for PET-RAFT polymerization under broad spectrum excitation
(Royal Society of Chemistry, 2021) Zhu, Yifan; Zhu, Dongyang; Chen, Yu; Yan, Qianqian; Liu, Chun-Yen; Ling, Kexin; Liu, Yifeng; Lee, Dongjoo; Wu, Xiaowei; Senftle, Thomas P.; Verduzco, Rafael
Covalent organic frameworks (COFs) are crystalline and porous organic materials attractive for photocatalysis applications due to their structural versatility and tunable optical and electronic properties. The use of photocatalysts (PCs) for polymerizations enables the preparation of well-defined polymeric materials under mild reaction conditions. Herein, we report two porphyrin-based donor–acceptor COFs that are effective heterogeneous PCs for photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT). Using density functional theory (DFT) calculations, we designed porphyrin COFs with strong donor–acceptor characteristics and delocalized conduction bands. The COFs were effective PCs for PET-RAFT, successfully polymerizing a variety of monomers in both organic and aqueous media using visible light (λmax from 460 to 635 nm) to produce polymers with tunable molecular weights (MWs), low molecular weight dispersity, and good chain-end fidelity. The heterogeneous COF PCs could also be reused for PET-RAFT polymerization at least 5 times without losing photocatalytic performance. This work demonstrates porphyrin-based COFs that are effective catalysts for photo-RDRP and establishes design principles for the development of highly active COF PCs for a variety of applications.
Rapid, Ambient Temperature Synthesis of Imine Covalent Organic Frameworks Catalyzed by Transition-Metal Nitrates
(American Chemical Society, 2021) Zhu, Dongyang; Zhang, Zhuqing; Alemany, Lawrence B.; Li, Yilin; Nnorom, Njideka; Barnes, Morgan; Khalil, Safiya; Rahman, Muhammad M.; Ajayan, Pulickel M.; Verduzco, Rafael
Covalent organic frameworks (COFs) are crystalline, porous organic materials that are promising for applications including catalysis, energy storage, electronics, gas storage, water treatment, and drug delivery. Conventional solvothermal synthesis approaches require elevated temperatures, inert environments, and long reaction times. Herein, we show that transition-metal nitrates can catalyze the rapid synthesis of imine COFs under ambient conditions. We first tested a series of transition metals for the synthesis of a model COF and found that all transition-metal nitrates tested produced crystalline COF products even in the presence of oxygen. Fe(NO3)3·9H2O was found to produce the most crystalline product, and crystalline COFs could be produced within 10 min by optimizing the catalyst loading. Fe(NO3)3·9H2O was further tested as a catalyst for six different COF targets varying in linker lengths, substituents, and stabilities, and it effectively catalyzed the synthesis of all imine COFs tested. This catalyst was also successful in the synthesis of 2D imine COFs with different geometries, 3D COFs, and azine-linked COFs. This work demonstrates a simple, low-cost approach for the synthesis of imine COFs and will significantly lower the barrier for the development of imine COFs for applications.
Synthesis, Activation, and Transformation of Covalent Organic Frameworks
(2021-04-28) Zhu, Dongyang; Verduzco, Rafael
Covalent organic frameworks (COFs) are an emerging class of organic, crystalline macromolecules. Due to their tunable chemistry, tailorable structure, regular pore channels and high surface areas, they have received significant attention for various applications, such as catalysis, energy storage, gas storage and separation, membrane separation and drug delivery. However, developing materials that can be used in these applications requires addressing a number of fundamental challenges in COF synthesis, activation, and transformation. In this thesis, we introduce new catalysts for the rapid synthesis of COFs under ambient conditions, novel strategies for synthesis that increase crystallinity, activation approaches that preserve the porosity even for fragile COFs, and transformation approaches that enable the conversion of linear polymers to COFs. The synthesis of crystalline and porous COFs remains a significant challenge. In Chapter 2, we demonstrate that a series of transition metal nitrates can be used to rapidly produce COFs under ambient conditions. These transition metal nitrates enabled the production of crystalline COFs within 10 minutes at room temperature, and were successfully used to synthesize a wide range of COF targets varying in linker chemistry, linker lengths, substituents, and stabilities. In Chapter 3, we demonstrate novel synthetic strategies to produce highly crystalline and porous COFs. We show that in the synthesis of imine COFs, benzaldehyde modulators compete with multi-functional aldehyde monomers to slow down the COF polymerization and growth chemistry. The modulators result in an improved crystallinity of the final COF, and the amount of benzaldehyde modulator added can be optimized for yield and product crystallinity. Activation of COFs generally involves washing and drying to isolate COFs from synthesis solvents and produce dry COF powders. Activation is as important as synthesis since COFs with high crystallinity and porosity can only be produced through proper activation. However, activation processes are usually overlooked, and conventional methods can result in collapse of porous structure and loss of accessible surface areas. In Chapter 4, we present a general approach to COF activation. We demonstrate that the use of an ultralow surface tension solvent perfluorohexane (PFH) enables rapid, simple and effective activation of a range of COFs. This approach avoids the use of supercritical CO2, which is not as widely accessible as PFH. In Chapter 5, we demonstrate a novel route to the synthesis of COFs through the transformation of linear polymers using dynamic and reversible chemistries. Specifically, we demonstrate an approach to transform linear imine-linked polymers into ketone-linked COFs through a linker replacement strategy with triformylphloroglucinol (TPG). TPG first reacts through dynamic chemistry to replace linkers in the linear polymers and then undergoes irreversible tautomerism to produce ketone linkages. This strategy provides an approach to synthesizing COFs through the solution processing of linear polymers followed by transformation to the desired COF structure. Finally, this thesis proposes future research directions based on the topics introduced from Chapter 2 to Chapter 5. We aim to develop more novel catalysts for COF synthesis and broaden their generality. We propose to modify the COF surface chemistry through the introduction of functionalized modulators and design more robust COFs through molecular engineering. We also aim to transform soluble linear polymers into COFs, which might serve as a novel solution processing method for COFs. We anticipate that these investigations provide further insight into the fundamental properties and basic problems in COF areas.
Three-dimensional covalent organic frameworks with pto and mhq-z topologies based on Tri- and tetratopic linkers
(Springer Nature, 2023) Zhu, Dongyang; Zhu, Yifan; Chen, Yu; Yan, Qianqian; Wu, Han; Liu, Chun-Yen; Wang, Xu; Alemany, Lawrence B.; Gao, Guanhui; Senftle, Thomas P.; Peng, Yongwu; Wu, Xiaowei; Verduzco, Rafael
Three-dimensional (3D) covalent organic frameworks (COFs) possess higher surface areas, more abundant pore channels, and lower density compared to their two-dimensional counterparts which makes the development of 3D COFs interesting from a fundamental and practical point of view. However, the construction of highly crystalline 3D COF remains challenging. At the same time, the choice of topologies in 3D COFs is limited by the crystallization problem, the lack of availability of suitable building blocks with appropriate reactivity and symmetries, and the difficulties in crystalline structure determination. Herein, we report two highly crystalline 3D COFs with pto and mhq-z topologies designed by rationally selecting rectangular-planar and trigonal-planar building blocks with appropriate conformational strains. The pto 3D COFs show a large pore size of 46 Å with an extremely low calculated density. The mhq-z net topology is solely constructed from totally face-enclosed organic polyhedra displaying a precise uniform micropore size of 1.0 nm. The 3D COFs show a high CO2 adsorption capacity at room temperature and can potentially serve as promising carbon capture adsorbents. This work expands the choice of accessible 3D COF topologies, enriching the structural versatility of COFs.
Transformation of One-Dimensional Linear Polymers into Two-Dimensional Covalent Organic Frameworks Through Sequential Reversible and Irreversible Chemistries
(American Chemical Society, 2021) Zhu, Dongyang; Li, Xiaoyi; Li, Yilin; Barnes, Morgan; Tseng, Chia-Ping; Khalil, Safiya; Rahman, Muhammad M.; Ajayan, Pulickel M.; Verduzco, Rafael
Covalent organic frameworks (COFs) are crystalline porous materials linked by dynamic covalent bonds. Dynamic chemistries enable the transformation of an initially amorphous network into a porous and crystalline COF. While dynamic chemistries have been leveraged to realize transformations between different types of COFs, including transformations from two-dimensional (2D) to three-dimensional (3D) COFs and insertion of different linking groups, the transformation of linear polymers into COFs has not yet been reported. Herein, we demonstrate an approach to transform linear imine-linked polymers into ketone-linked COFs through a linker replacement strategy with triformylphloroglucinol (TPG). TPG first reacts through dynamic chemistry to replace linkers in the linear polymers and then undergoes irreversible tautomerism to produce ketone linkages. We have analyzed the time-dependent transformation from the linear polymer into COF through powder X-ray diffraction, Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) to understand the transition and substitution mechanisms. This work demonstrates another route to produce COFs through sequential reversible and irreversible chemistries and provides a potential approach to synthesizing COFs through the solution processing of linear polymers followed by transformation into the desired COF structure.
Understanding fragility and engineering activation stability in two-dimensional covalent organic frameworks
(Royal Society of Chemistry, 2022) Zhu, Dongyang; Zhang, Jun-Jie; Wu, Xiaowei; Yan, Qianqian; Liu, Fangxin; Zhu, Yifan; Gao, Xiaodong; Rahman, Muhammad M.; Yakobson, Boris I.; Ajayan, Pulickel M.; Verduzco, Rafael
The sensitivity of covalent organic frameworks (COFs) to pore collapse during activation processes is generally termed activation stability, and activation stability is important for achieving and maintaining COF crystallinity and porosity which are relevant to a variety of applications. However, current understanding of COF stability during activation is insufficient, and prior studies have focused primarily on thermal stability or on the activation stability of other porous materials, such as metal–organic frameworks (MOFs). In this work, we demonstrate and implement a versatile experimental approach to quantify activation stability of COFs and use this to establish a number of relationships between their pore size, the type of pore substituents, pore architecture, and structural robustness. Additionally, density functional theory calculations reveal the impact on both inter-and intra-layer interactions, which govern activation stability, and we demonstrate that activation stability can be systematically tuned using a multivariate synthesis approach involving mixtures of functionalized and unfunctionalized COF building blocks. Our findings provide novel fundamental insights into the activation stability of COFs and offer guidance for the design of more robust COFs.

Browsing by Author "Zhu, Dongyang"

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