Porous Networks Assembled from Octaphenylsilsesquioxane Building Blocks

Synthesis of Sulfonated Phenylsilsesquioxanes Guided by Machine Learning

Sulfonated octaphenylsilsesquioxane (SPOSS) has garnered significant interest due to its unique structural properties of containing the -SO3H group and its wide range of applications. This study introduces a novel approach to the synthesis of SPOSS, leveraging machine learning algorithms to explore new recipes and achieve higher -SO3H functionality. The focus was on synthesizing SPOSS with 2, 4, 6, and 8-SO3H functional groups on the phenyl group, marked as SPOSS-2, SPOSS-4, SPOSS-6, and SPOSS-8, respectively. The successful synthesis of SPOSS-8 was achieved by 5 training outputs based on the recipes of 21 sets of low-functionality (<4) SPOSS. The structure of SPOSS was confirmed using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and time-of-flight mass spectrometry (MALDI-TOF MS). Machine learning analysis revealed that K2SO4 is an important additive to improve the functionality of SPOSS. A synthetic mechanism was proposed and validated that K2SO4 participated in the reaction to generate sulfur trioxide (SO3), a sulfonating agent with high reactivity. SPOSS shows thermal stability superior to octaphenylsilsesquioxane (OPS) according to thermogravimetric analysis (TGA) and TG-FTIR.

Direct cross-linking of silyl-functionalized cage siloxanes via nonhydrolytic siloxane bond formation for preparing nanoporous materials

Bottom-up synthesis of siloxane-based nanoporous materials from siloxane oligomers is promising for constructing well-defined structures at a molecular level. Herein, we report the synthesis of nanoporous materials consisting of cage-type siloxanes through the nonhydrolytic siloxane bond formation reaction. Cage siloxanes with double-n-ring geometries (n = 4 or 6) modified with dimethylsilyl and dimethylethoxysilyl groups are synthesized and directly cross-linked using a B(C6F5)3 catalyst, resulting in the formation of porous networks composed of alternating cage siloxane nodes and tetramethyldisiloxane (-SiMe2OSiMe2-) linkers. Compared with conventional hydrolysis and polycondensation reactions of alkoxysilyl-modified cage siloxanes under acid conditions, the non-hydrolytic condensation reaction was found favorable for the formation of porous siloxane networks without unwanted cleavage of the siloxane bonds.

Formation of nanostructured silicas through the fluoride catalysed self-polymerization of Q-type functional silica cages

Octa(dimethylsiloxy)silica cages (Q₈M₈^H) undergo rapid self-polymerization in the presence of a fluoride catalyst to form complex 3D porous structural network materials with specific surface areas up to 650 m² g^-1. This establishes a new method to form bio-derived high inorganic content soft silicas with potential applications in filtration, carbon capture, catalysis, or hydrogen source.

Unconventional Conjugation in macromonomers and polymers

Multiple reviews have been written concerning conjugated macromonomers and polymers both as general descriptions and for specific applications. In most examples, conjugation occurs via elec-tronic communication via continuous overlap of...

Modeling of Hydrogen Storage Utilizing Silsesquioxane Cages: Adsorption and Quasi-Dynamic Simulations of Encapsulation of H2 Molecule into Silsesquioxane Cages

Solid-state hydrogen storage may be the only promising way for mobile applications of hydrogen energy since it is safe, quickly reversible, cost-efficient, and has a high volumetric energy density under standard conditions. Silsesquioxane and its derivatives seem well suited for solid-state hydrogen storage and have attracted many experimental and theoretical researchers. In the present work, we have systematically studied four cages of T8, T10, and T12 (D_2d and D_6h) for hydrogen storage including adsorption and encapsulation of hydrogen molecules. We find that silsesquioxane cages have up to about 4150 m²/g specific surface area (SSA) and 7.81 wt % for hydrogen storage. These calculated values are comparable to the highest hydrogen storage values of metal-organic frameworks, porous polymer networks, and covalent organic frameworks. In addition, we use the quasi-dynamic method to study the encapsulation of hydrogen molecules into these cages because of the timescale limitation of ab initio molecular dynamics. Thermodynamic parameters such as enthalpy and Gibbs free energy at different temperatures are calculated during the insertion processes. We find that the insertion process of a hydrogen molecule into the T12 (D_6h) cage is almost energy-conserved and its energy barriers of enthalpy and free energy are moderate under standard conditions.

Alkoxy- and Silanol-Functionalized Cage-Type Oligosiloxanes as Molecular Building Blocks to Construct Nanoporous Materials

Siloxane-based materials have a wide range of applications. Cage-type oligosiloxanes have attracted significant attention as molecular building blocks to construct novel siloxane-based nanoporous materials with promising applications such as in catalysis and adsorption. This paper reviews recent progress in the preparation of siloxane-based nanoporous materials using alkoxy- and silanol-functionalized cage siloxanes. The arrangement of cage siloxanes units is controlled by various methods, including amphiphilic self-assembly, hydrogen bonding of silanol groups, and regioselective functionalization, toward the preparation of ordered nanoporous siloxane-based materials.

Facile and selective synthesis of zeolites L and W from a single-source heptanuclear aluminosilicate precursor

Zeolites L and W were synthesized for the first time from a heptanuclear aluminosilicate complex as a single-source molecular precursor, highlighting the potential versatility of this approach toward the synthesis of a variety of zeolites.

Anthracene–styrene-substituted m-carborane derivatives: insights into the electronic and structural effects of substituents on photoluminescence

Efficient light emitters based on anthracene derivatives were developed. We prove that m-carborane is a perfect scaffold for coupling to anthracene giving rise to superb emitters in solution, while keeping the emission properties in aggregate state.

Synthesis of Polycyclic and Cage Siloxanes by Hydrolysis and Intramolecular Condensation of Alkoxysilylated Cyclosiloxanes

The controlled synthesis of oligosiloxanes with well-defined structures is important for the bottom-up design of siloxane-based nanomaterials. This work reports the synthesis of various polycyclic and cage siloxanes by the hydrolysis and intramolecular condensation of monocyclic tetra- and hexasiloxanes functionalized with various alkoxysilyl groups. An investigation of monoalkoxysilylated cyclosiloxanes revealed that intramolecular condensation occurred preferentially between adjacent alkoxysilyl groups to form new tetrasiloxane rings. The study of dialkoxy- and trialkoxysilylated cyclotetrasiloxanes revealed multistep intramolecular condensation reactions to form cubic octasiloxanes in relatively high yields. Unlike conventional methods starting from organosilane monomers, intramolecular condensation enables the introduction of different organic substituents in controlled arrangements. So-called Janus cubes have been successfully obtained, that is, Ph₄ R₄ Si₈ O₁₂ , in which R=Me, OSiMe₃ , and OSiMe₂ Vi (Vi=vinyl). These findings will enable the creation of siloxane-based materials with diverse functions.

Porous Silsesquioxane-Imine Frameworks as Highly Efficient Adsorbents for Cooperative Iodine Capture

The efficient capture and storage of radioactive iodine (¹²⁹I or ¹³¹I), which can be formed during nuclear energy generation or nuclear waste storage, is of paramount importance. Herein, we present highly efficient aerogels for reversible iodine capture, namely, porous silsesquioxane-imine frameworks (PSIFs), constructed by condensation of octa(3-aminopropyl)silsesquioxane cage compound and selected multitopic aldehydes. The resulting PSIFs are permanently porous (Brunauer-Emmet-Teller surface areas up to 574 m²/g), thermally stable, and present a combination of micro-, meso-, and macropores in their structures. The presence of a large number of imine functional groups in combination with silsesquioxane cores results in extremely high I₂ affinity with uptake capacities up to 485 wt %, which is the highest reported to date. Porous properties can be controlled by the strut length and rigidity of linkers. In addition, PSIF-1a could be recycled at least four times while maintaining 94% I₂ uptake capacity. Kinetic studies of I₂ desorption show two strong binding sites with apparent activation energies of 77.0 and 89.0 kJ/mol. These energies are considerably higher than the enthalpy of sublimation of bulk I₂.

Organosilica hybrid nanomaterials with a high organic content: syntheses and applications of silsesquioxanes

Organic-inorganic hybrid materials garner properties from their organic and inorganic matrices as well as synergistic features, and therefore have recently attracted much attention at the nanoscale. Non-porous organosilica hybrid nanomaterials with a high organic content such as silsesquioxanes (R-SiO_1.5, with R organic groups) and bridged silsesquioxanes (O_1.5Si-R-SiO_1.5) are especially attractive hybrids since they provide 20 to 80 weight percent of organic functional groups in addition to the known chemistry and stability of silica. In the organosilica family, silsesquioxanes (R-SiO_1.5) stand between silicas (SiO₂) and silicones (R₂SiO), and are variously called organosilicas, ormosil (organically-modified silica), polysilsesquioxanes and silica hybrids. Herein, we comprehensively review non-porous silsesquioxane and bridged silsesquioxane nanomaterials and their applications in nanomedicine, electro-optics, and catalysis.

Tunable Gravimetric and Volumetric Hydrogen Storage Capacities in Polyhedral Oligomeric Silsesquioxane Frameworks

We study the hydrogen adsorption in porous frameworks composed of silsesquioxane cages linked via boron substituted aromatic structures by first-principles modeling. Such polyhedral oligomeric silsesquioxane (POSS) frameworks can be further modified by decorating them with metal atoms binding to the ring structures of the linkers. We have considered Sc- and Ti-doped frameworks which bind H2 via so-called Kubas interaction between hydrogen molecules and transition metal atoms. It will be demonstrated that the maximum H2 gravimetric capacity can be improved to more than 7.5 wt % by using longer linkers with more ring structures. However, the maximum H2 volumetric capacity can be tuned to more than 70 g/L by varying the size of silsesquioxane cages. We are optimistic that by varying the building blocks, POSS frameworks can be modified to meet the targets for the gravimetric and volumetric capacities set by the U.S. Department of Energy.

Lanthanide complex-functionalized polyhedral oligomeric silsesquioxane with multicolor emission covered from 450 nm to 1700 nm

Six new hybrid materials covalently linking ternary lanthanide complexes to POSS were prepared, and the luminescent properties were investigated in detail.

Synthesis of aromatic functionalized cage-rearranged silsesquioxanes (T8, T10, and T12) via nucleophilic substitution reactions

Organic-inorganic hybrid nano-building blocks of aromatic nitro-, aldehyde-, and bromo-functionalized polyhedral oligomeric silsesquioxanes were easily prepared through nucleophilic substitutions, starting from the reactions between octakis(3-chloropropyl)octasilsesquioxane and phenoxide derivatives. These phenoxide anions not only supply the substitution functions to a silsesquioxane cage, but can also induce a cage-rearrangement leading to the formation of octa-, deca-, and dodecahedral silsesquioxane cages.

Regular assembly of cage siloxanes by hydrogen bonding of dimethylsilanol groups

A new class of ordered silica-based materials has been prepared by assembly of cage siloxanes with hydrogen bonds of dimethylsilanol groups at their corners.

Octavinylsilsesquioxane-based luminescent nanoporous inorganic–organic hybrid polymers constructed by the Heck coupling reaction

A class of luminescent nanoporous inorganic–organic hybrid polymers has been synthesized by the Heck coupling of octavinylsilsesquioxane with aromatic bromide monomers. The resulting materials exhibit porous and luminescent features, and show picric acid sensing behaviour.

Constructing hybrid porous polymers from cubic octavinylsilsequioxane and planar halogenated benzene

Hybrid porous polymers derived from cubic octavinylsilsequioxane and planar halogenated benzene monomers exhibit high thermal stability, tunable porosities and potential applications in carbon dioxide storage.

Mesostructured nanomagnetic polyhedral oligomeric silsesquioxanes (POSS) incorporated with dithiol organic anchors for multiple pollutants capturing in wastewater

A functionalizable organosiliceous hybrid magnetic material was facilely constructed by surface polymerization of octavinyl polyhedral oligomeric silsesquioxane (POSS) on the Fe3O4 nanoparticles. The resultant Fe3O4@POSS was identified as a mesoporous architecture with an average particle diameter of 20 nm and high specific surface area up to 653.59 m(2) g(-1). After it was tethered with an organic chain containing dithiol via thiol-ene addition reaction, the ultimate material (Fe3O4@POSS-SH) still have moderate specific area (224.20 m(2) g(-1)) with almost identical porous morphology. It turns out to be a convenient, efficient single adsorbent for simultaneous elimination of inorganic heavy metal ions and organic dyes in simulate multicomponent wastewater at ambient temperature. The Fe3O4@POSS-SH nanoparticles can be readily withdrawn from aqueous solutions within a few seconds under moderate magnetic field and exhibit good stability in strong acid and alkaline aqueous matrices. Contaminants-loaded Fe3O4@POSS-SH can be easily regenerated with either methanol-acetic acid (for organic dyes) or hydrochloric acid (for heavy metal ions) under ultrasonication. The renewed one keeps appreciable adsorption capability toward both heavy metal ions and organic dyes, the removal rate for any of the pollutants exceeds 92% to simulate wastewater with multiple pollutants after repeated use for 5 cycles. Beyond the environmental remediation function, thanks to the pendant vinyl groups, the Fe3O4@POSS derived materials rationally integrating distinct or versatile functions could be envisaged and consequently a wide variety of applications may emerge.

Conceptual design of large surface area porous polymeric hybrid media based on polyhedral oligomeric silsesquioxane precursors: preparation, tailoring of porous properties, and internal surface functionalization

We report on the preparation of hybrid, organic-inorganic porous materials derived from polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) via a single-step molding process. The monolithic, large surface area materials are studied with a particular focus on morphology and porous properties. Radical vinyl polymerization of the nanometer-sized POSS building blocks is therefore utilized via a thermally initiated route and in porogenic diluents such as tetrahydrofuran and polyethylene glycols of varying composition. Careful choice of these porogenic solvents and proper choice of initiator concentration lead to highly porous monolithic building entities which show a rigid, 3D-adhered, porous structure, macroscopically adapting the shape of a given mold. The described materials reflect Brunauer-Emmett-Teller (BET) surface areas of 700 m2/g or more and maximum tunable mesopore volumes of up to 2 cm3/g. Experimental investigations demonstrate the option to tailor nanoporosity and macroporosity in the single-step free-radical polymerization process. While studies on the influence of the used porogenic solvents reveal tuneability of pore sizes due to the unique pore formation process, tailored existence of residual vinyl groups allows facile postpolymerization modification of the highly porous, large surface area hybrid materials exploited via thiol-ene "click" chemistry. Our developed, simply realizable preparation process explores a new route to derive porous organic-inorganic hybrid adsorbents for a wide variety of applications such as extraction, separation science, and catalysis.

A new, higher yielding synthetic route towards dodecaphenyl cage silsesquioxanes: synthesis and mechanistic insights

Cage dodecaphenylsilsesquioxane (T12-Phenyl) was synthesized in a one batch, mildly basic aqueous solution under room temperature conditions using a trialkoxysilane precursor. Significant improvements in synthetic yield (>95%) were observed compared with previous reports. Kinetic studies of the hydrolysis of phenyltrimethoxysilane were conducted and the condensation was monitored by (29)Si NMR which revealed the presence of a transient, intermediary T1 species as the pathway to dodecaphenylsilsesquioxane spherulites, and the tendency for T12 structures over T8, T10, and other substructures was explained through MM2 simulations.