scholarly journals Control of extrinsic porosities in linked metal-organic polyhedra gels by imparting coordination-driven self-assembly with electrostatic repulsion

2022 ◽  
Author(s):  
Zaoming Wang ◽  
Takuma Aoyama ◽  
Eli Sanchez-Gonzales ◽  
Tomoko Inose ◽  
Kenji Urayama ◽  
...  
Keyword(s):  
Self Assembly ◽  
Molecular Level ◽  
Amorphous State ◽  
Soft Materials ◽  
Internal Cavity ◽  
Hydroxyl Groups ◽  
Electrostatic Repulsion ◽  
Outer Periphery ◽  
Metal Organic

The linkage of metal-organic polyhedra (MOPs) for the synthesis of porous soft materials is one of the promising strategies to combine processability with permanent porosity. Compared to the defined internal cavity of MOPs, it is still difficult to control the extrinsic porosities generated between crosslinked MOPs because of their random arrangements in their networks. Herein, we report a method to form linked MOP gels with controllable extrinsic porosities by introducing negative charges on the surface of MOPs that facilitates electrostatic repulsion between them. A hydrophilic rhodium-based cuboctahedral MOP (OHRhMOP) with 24 hydroxyl groups on its outer periphery can be controllably deprotonated to impart the MOP with tunable electrostatic repulsion in solution. This electrostatic repulsion between MOPs stabilizes the kinetically trapped state, in which a MOP is coordinated with various bisimidazole linkers in a monodentate fashion at a controllable link-er/MOP ratio. The heating of the kinetically trapped molecules leads to the formation of gels with similar colloidal networks but different extrinsic porosity. This strategy allows us to design the molecular-level networks and the resulting porosities even in the amorphous state.

scholarly journals Porous Colloidal Hydrogels Formed by Coordination-Driven Self-Assembly of Charged Metal-Organic Polyhedra

2021 ◽  
Author(s):  
Zaoming Wang ◽  
Gavin Craig ◽  
alexandre legrand ◽  
Frederik Haase ◽  
Saori Minami ◽  
...  
Keyword(s):  
Self Assembly ◽  
Soft Materials ◽  
Building Blocks ◽  
Internal Cavity ◽  
Hydroxyl Groups ◽  
Gel Formation ◽  
Gas Sorption ◽  
Coordination Cages ◽  
Metal Organic ◽  
Supramolecular Polymerization

Introduction of porosity into supramolecular gels endows soft materials with functionalities for molecular encapsulation, release, separation and conversion. Metal-organic polyhedra (MOPs), discrete coordination cages containing an internal cavity, have recently been employed as building blocks to construct polymeric gel networks with potential porosity. However, most of the materials can only be synthesized in organic solvents, and the examples of porous, MOP-based hydrogels are scarce. Here, we demonstrate the fabrication of porous hydrogels based on [Rh<sub>2</sub>(OH-bdc)<sub>2</sub>]<sub>12</sub>, a rhodium-based MOP containing hydroxyl groups on its periphery (OH-bdc = 5-hydroxy-1,3-benzenedicarboxylate). By simply deprotonating [Rh<sub>2</sub>(OH-bdc)<sub>2</sub>]<sub>12</sub> with the base NaOH, the supramolecular polymerization between MOPs and organic linkers can be induced in the aqueous solution, leading to the kinetically controllable formation of hydrogels with hierarchical colloidal networks. When heating the deprotonated MOP, Na<sub>x</sub>[Rh<sub>24</sub>(O-bdc)<sub>x</sub>(OH-bdc)<sub>24-x</sub>], to induce gelation, the MOP was found to partially decompose, affecting the mechanical property of the resulting gels. By applying a post-synthetic deprotonation strategy, we show that the deprotonation degree of the MOP can be altered after the gel formation without serious decomposition of the MOPs. Gas sorption measurements confirmed the permanent porosity of the corresponding aerogels obtained from these MOP-based hydrogels, showing potentials for applications in gas sorption and catalysis.

scholarly journals Porous Colloidal Hydrogels Formed by Coordination-Driven Self-Assembly of Charged Metal-Organic Polyhedra

2021 ◽  
Author(s):  
Zaoming Wang ◽  
Gavin Craig ◽  
alexandre legrand ◽  
Frederik Haase ◽  
Saori Minami ◽  
...  
Keyword(s):  
Self Assembly ◽  
Soft Materials ◽  
Building Blocks ◽  
Internal Cavity ◽  
Hydroxyl Groups ◽  
Gel Formation ◽  
Gas Sorption ◽  
Coordination Cages ◽  
Metal Organic ◽  
Supramolecular Polymerization

Introduction of porosity into supramolecular gels endows soft materials with functionalities for molecular encapsulation, release, separation and conversion. Metal-organic polyhedra (MOPs), discrete coordination cages containing an internal cavity, have recently been employed as building blocks to construct polymeric gel networks with potential porosity. However, most of the materials can only be synthesized in organic solvents, and the examples of porous, MOP-based hydrogels are scarce. Here, we demonstrate the fabrication of porous hydrogels based on [Rh<sub>2</sub>(OH-bdc)<sub>2</sub>]<sub>12</sub>, a rhodium-based MOP containing hydroxyl groups on its periphery (OH-bdc = 5-hydroxy-1,3-benzenedicarboxylate). By simply deprotonating [Rh<sub>2</sub>(OH-bdc)<sub>2</sub>]<sub>12</sub> with the base NaOH, the supramolecular polymerization between MOPs and organic linkers can be induced in the aqueous solution, leading to the kinetically controllable formation of hydrogels with hierarchical colloidal networks. When heating the deprotonated MOP, Na<sub>x</sub>[Rh<sub>24</sub>(O-bdc)<sub>x</sub>(OH-bdc)<sub>24-x</sub>], to induce gelation, the MOP was found to partially decompose, affecting the mechanical property of the resulting gels. By applying a post-synthetic deprotonation strategy, we show that the deprotonation degree of the MOP can be altered after the gel formation without serious decomposition of the MOPs. Gas sorption measurements confirmed the permanent porosity of the corresponding aerogels obtained from these MOP-based hydrogels, showing potentials for applications in gas sorption and catalysis.

Spatiotemporal Control of Supramolecular Polymerization and Gelation of Metal-Organic Polyhedra

2020 ◽  
Author(s):  
alexandre legrand ◽  
Li-Hao Liu ◽  
Philipp Royla ◽  
Takuma Aoyama ◽  
Gavin Craig ◽  
...  
Keyword(s):  
Acid Concentration ◽  
Self Assembly ◽  
Colloidal Particles ◽  
Soft Materials ◽  
Supramolecular Materials ◽  
Time Resolved ◽  
Colloidal Gel ◽  
Metal Organic ◽  
Spatiotemporal Control ◽  
Gel Network

In coordination-based supramolecular materials such as metallogels, simultaneous temporal and spatial control of their assembly remains challenging. Here, we demonstrate that the combination of light with acids as stimuli allows for the spatiotemporal control over the architectures, mechanical properties, and shape of porous soft materials based on metal-organic polyhedra (MOPs). First, we show that the formation of a colloidal gel network from a preformed kinetically trapped MOP solution can be triggered upon addition of trifluoroacetic acid (TFA), and that acid concentration determines the reaction kinetics. As determined by time-resolved dynamic light scattering, UV-vis absorption and <sup>1</sup>H NMR spectroscopies and rheology measurements, the consequences of the increase in acid concentration are (i) an increase in the cross-linking between MOPs; (ii) a growth in the size of the colloidal particles forming the gel network; (iii) an increase in the density of the colloidal network; and (iv) a decrease in the ductility and stiffness of the resulting gel. We then demonstrate that irradiation of a dispersed photoacid generator, pyranine, allows the spatiotemporal control of the gel formation by locally triggering the self-assembly process. Using this methodology, we show that the gel can be patterned into a desired shape. Such precise positioning of the assembled structures, combined with the stable and permanent porosity of MOPs, could allow their integration into devices for applications such as sensing, separation, catalysis, or drug release.

scholarly journals Understanding of the Multiscale Self-Assembly of Metal-Organic Polyhedra Towards Functionally Graded Porous Gels

2019 ◽  
Author(s):  
alexandre legrand ◽  
Gavin A. Craig ◽  
Mickaele Bonneau ◽  
Saori Minami ◽  
Kenji Urayama ◽  
...  
Keyword(s):  
Self Assembly ◽  
Energy Transport ◽  
Soft Materials ◽  
Functionally Graded ◽  
Colloidal Gels ◽  
Time Resolved ◽  
Colloidal Aggregation ◽  
Synthetic Materials ◽  
Multiple Length Scales ◽  
Metal Organic

Spatial heterogeneity and gradients within porous materials are key for controlling their mechanical properties and mass/energy transport, both in biological and synthetic materials. However, it is still challenging to induce such complexity in well-defined microporous materials such as crystalline metal-organic frameworks (MOFs). Here we show a method to generate a continuous gradient of porosity over multiple length scales by taking advantage of the amorphous nature of supramolecular polymers based on metal-organic polyhedra (MOPs). First, we use time-resolved dynamic light scattering (TRDLS) to elucidate the mechanism of hierarchical self-assembly of MOPs into colloidal gels and to understand the relationship between the MOP concentrations and the architecture of the resulting colloidal networks. These features directly impact on the viscoelastic response of the gels and their mechanical strength. We then show that gradients of stiffness and porosity can be created within the gel by applying centrifugal force at the point of colloidal aggregation. These results with the creation of asymmetric and graded pore configuration in soft materials could lead to the emergence of advanced properties that are coupled to asymmetric molecule/ion transport as seen in biological systems.<br>

scholarly journals Spatiotemporal Control of Supramolecular Polymerization and Gelation of Metal-Organic Polyhedra

2020 ◽  
Author(s):  
alexandre legrand ◽  
Li-Hao Liu ◽  
Philipp Royla ◽  
Takuma Aoyama ◽  
Gavin Craig ◽  
...  
Keyword(s):  
Acid Concentration ◽  
Self Assembly ◽  
Colloidal Particles ◽  
Soft Materials ◽  
Supramolecular Materials ◽  
Time Resolved ◽  
Colloidal Gel ◽  
Metal Organic ◽  
Spatiotemporal Control ◽  
Gel Network

In coordination-based supramolecular materials such as metallogels, simultaneous temporal and spatial control of their assembly remains challenging. Here, we demonstrate that the combination of light with acids as stimuli allows for the spatiotemporal control over the architectures, mechanical properties, and shape of porous soft materials based on metal-organic polyhedra (MOPs). First, we show that the formation of a colloidal gel network from a preformed kinetically trapped MOP solution can be triggered upon addition of trifluoroacetic acid (TFA), and that acid concentration determines the reaction kinetics. As determined by time-resolved dynamic light scattering, UV-vis absorption and <sup>1</sup>H NMR spectroscopies and rheology measurements, the consequences of the increase in acid concentration are (i) an increase in the cross-linking between MOPs; (ii) a growth in the size of the colloidal particles forming the gel network; (iii) an increase in the density of the colloidal network; and (iv) a decrease in the ductility and stiffness of the resulting gel. We then demonstrate that irradiation of a dispersed photoacid generator, pyranine, allows the spatiotemporal control of the gel formation by locally triggering the self-assembly process. Using this methodology, we show that the gel can be patterned into a desired shape. Such precise positioning of the assembled structures, combined with the stable and permanent porosity of MOPs, could allow their integration into devices for applications such as sensing, separation, catalysis, or drug release.

scholarly journals Understanding of the Multiscale Self-Assembly of Metal-Organic Polyhedra Towards Functionally Graded Porous Gels

2019 ◽  
Author(s):  
alexandre legrand ◽  
Gavin A. Craig ◽  
Mickaele Bonneau ◽  
Saori Minami ◽  
Kenji Urayama ◽  
...  
Keyword(s):  
Self Assembly ◽  
Energy Transport ◽  
Soft Materials ◽  
Functionally Graded ◽  
Colloidal Gels ◽  
Time Resolved ◽  
Colloidal Aggregation ◽  
Synthetic Materials ◽  
Multiple Length Scales ◽  
Metal Organic

Spatial heterogeneity and gradients within porous materials are key for controlling their mechanical properties and mass/energy transport, both in biological and synthetic materials. However, it is still challenging to induce such complexity in well-defined microporous materials such as crystalline metal-organic frameworks (MOFs). Here we show a method to generate a continuous gradient of porosity over multiple length scales by taking advantage of the amorphous nature of supramolecular polymers based on metal-organic polyhedra (MOPs). First, we use time-resolved dynamic light scattering (TRDLS) to elucidate the mechanism of hierarchical self-assembly of MOPs into colloidal gels and to understand the relationship between the MOP concentrations and the architecture of the resulting colloidal networks. These features directly impact on the viscoelastic response of the gels and their mechanical strength. We then show that gradients of stiffness and porosity can be created within the gel by applying centrifugal force at the point of colloidal aggregation. These results with the creation of asymmetric and graded pore configuration in soft materials could lead to the emergence of advanced properties that are coupled to asymmetric molecule/ion transport as seen in biological systems.<br>

Kinetic Control of Interpenetration in Fe-Biphenyl-4,4′-dicarboxylate MOFs by Coordination and Oxidation Modulation

2018 ◽  
Author(s):  
Dominic Bara ◽  
Claire Wilson ◽  
Max Mörtel ◽  
Marat M. Khusniyarov ◽  
ben slater ◽  
...  
Keyword(s):  
Self Assembly ◽  
Surface Areas ◽  
Metal Precursors ◽  
Additional Coordination ◽  
Fine Control ◽  
Multiple Alternative ◽  
Metal Organic ◽  
Dft Simulations ◽  
High Valent ◽  
And Control

Phase control in the self-assembly of metal-organic frameworks (MOFs) – materials wherein organic ligands connect metal ions or clusters into network solids with potential porosity – is often a case of trial and error. Judicious control over a number of synthetic variables is required to select for the desired topology and control features such as interpenetration and defectivity, which have significant impact on physical properties and application. Herein, we present a comprehensive investigation of self-assembly in the Fe-biphenyl-4,4'-dicarboxylate system, demonstrating that coordination modulation, the addition of competing ligands into solvothermal syntheses, can reliably tune between the kinetic product, non-interpenetrated MIL-88D(Fe), and the thermodynamic product, two-fold interpenetrated MIL-126(Fe). DFT simulations reveal that correlated disorder of the terminal anions on the metal clusters in the interpentrated phase results in H-bonding between adjacent nets and is the thermodynamic driving force for its formation. Coordination modulation slows self-assembly and therefore selects the thermodynamic product MIL-126(Fe), while offering fine control over defectivity, inducing mesoporosity, but electron microscopy shows the MIL-88D(Fe) phase persists in many samples despite not being evident in diffraction experiments, suggesting its presence accounts for the lower than predicted surface areas reported for samples to date. Interpenetration control is also demonstrated by utilizing the 2,2'-bipyridine-5,5'-dicarboxylate linker; DFT simulations show that it is energetically prohibitive for it to adopt the twisted conformation required to form the interpenetrated phase, and are confirmed by experimental data, although multiple alternative phases are identified due to additional coordination of the Fe cations to the N-donors of the ligand. Finally, we introduce oxidation modulation – the concept of using metal precursors in a different oxidation state to that found in the final MOF – as a further protocol to kinetically control self-assembly. Combining coordination and oxidation modulation allows the synthesis of pristine MIL-126(Fe) with BET surface areas close to the predicted maximum capacity for the first time, suggesting that combining the two may be a powerful methodology for the controlled self-assembly of high-valent MOFs.<br><br>

scholarly journals Mechanochemistry unveils stress transfer during sacrificial bond fracture of tough multiple network elastomers

2021 ◽  
Author(s):  
Yinjun Chen ◽  
Gabriel Sanoja ◽  
Costantino Creton
Keyword(s):  
Molecular Level ◽  
Stress Transfer ◽  
Soft Materials ◽  
Multiple Network

The molecular level transfer of stress from a stiff percolating filler to a stretchable matrix is a crucial and generic mechanism of toughening in soft materials.

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