Tailor‐Made Hybrid Organic–Inorganic Porous Materials Based on Polyhedral Oligomeric Silsesquioxanes (POSS) by the Step‐Growth Mechanism of Thiol‐Ene “Click” Chemistry

Synthetic Nanoarchitectonics of Functional Organic-Inorganic 2D Germanane Heterostructures via Click Chemistry

Succeeding graphene, 2D inorganic materials made of reactive van der Waals layers, like 2D germanane (2D-Ge) derivatives, have attracted great attention because their physicochemical characteristics can be entirely tuned by modulating the nature of the surface substituent. Although very interesting from a scientific point of view, almost all the reported works involving 2D-Ge derivatives are focused on computational studies. Herein, a first prototype of organic-inorganic 2D-Ge heterostructure has been synthesized by covalently anchoring thiol-rich carbon dots (CD-SH) onto 2D allyl germanane (2D-aGe) via a simple and green "one-pot" click chemistry approach. Remarkably, the implanted characteristics of the carbon nanomaterial provide new physicochemical features to the resulting 0D/2D heterostructure, making possible its implementation in yet unexplored optoelectronic tasks-e.g., as a fluorescence resonance energy transfer (FRET) sensing system triggered by supramolecular π-π interactions-that are inaccessible for the pristine 2D-aGe counterpart. Consequently, this work builds a foundation toward the robust achievement of functional organic-inorganic 2D-Ge nanoarchitectonics through covalently assembling thiol-rich carbon nanoallotropes on commercially available 2D-aGe.

Development of a highly efficient in-tube solid-phase microextraction system coupled with UHPLC-MS/MS for analyzing trace hydroxyl polycyclic aromatic hydrocarbons in biological samples

Hydroxyl polycyclic aromatic hydrocarbons are considered active mutagenic and carcinogenic substances and are found in extremely low levels (ng/g) in biological samples. As a result, their determination in urine and blood samples is challenging, and a sensitive and effective method for the analysis of trace hydroxyl polycyclic aromatic hydrocarbons in complex biological matrices is required. In this work, a novel macroporous in-tube solid-phase microextraction monolith was prepared via a thiol-yne click reaction, and a highly efficient analytical method based on in-tube solid-phase microextraction coupled with UHPLC-MS/MS was developed to determine hydroxyl polycyclic aromatic hydrocarbons with low detection limits of 0.137-11.0 ng/L in complex biological samples. Four hydroxyl polycyclic aromatic hydrocarbons, namely, 2-hydroxyanthraquinone, 1-hydroxypyrene, 1,8-dihydroxyanthraquinone, and 6-hydroxychrysene, were determined in the urine samples of smokers, non-smokers, and whole blood samples of mice. Satisfactory recoveries were achieved in the range of 83.1-113% with relative standard deviations of 3.2-9.7%. It was found that implementation of the macroporous monolith gave a highly efficient approach for enriching trace hydroxyl polycyclic aromatic hydrocarbons in biological samples.

Vinyl-Functionalized Janus Ring Siloxane: Potential Precursors to Hybrid Functional Materials

A vinyl-functionalized all-cis-tetrasiloxycyclotetrasiloxane [ViSi(OSiMe2H)O]4 (Vi = vinyl group) Janus precursor was prepared from potassium cyclotetrasiloxane silanolate. The Janus precursor was selectively modified at its dimethylhydrosilyl groups [-SiMe2H] via the Piers-Rubinsztajn reaction to obtain a family of new tetravinyl-substituted Janus rings [ViSi(OR')O]4 containing various functional groups in moderate yields. Remarkably, the tetravinyl groups on the structure remained intact after modification by the Piers-Rubinsztajn reaction. Since these synthesized compounds possess multiple functional groups (up to eight per molecule), they are potential precursors for advanced hybrid organic-inorganic functional materials.

Morphology Control and Metallization of Porous Polymers Synthesized by Michael Addition Reactions of a Multi-Functional Acrylamide with a Diamine

Porous polymers have been synthesized by an aza-Michael addition reaction of a multi-functional acrylamide, N,N',N″,N‴-tetraacryloyltriethylenetetramine (AM4), and hexamethylene diamine (HDA) in H2O without catalyst. Reaction conditions, such as monomer concentration and reaction temperature, affected the morphology of the resulting porous structures. Connected spheres, co-continuous monolithic structures and/or isolated holes were observed on the surface of the porous polymers. These structures were formed by polymerization-induced phase separation via spinodal decomposition or highly internal phase separation. The obtained porous polymers were soft and flexible and not breakable by compression. The porous polymers adsorbed various solvents. An AM4-HDA porous polymer could be plated by Ni using an electroless plating process via catalyzation by palladium (II) acetylacetonate following reduction of Ni ions in a plating solution. The intermediate Pd-catalyzed porous polymer promoted the Suzuki-Miyaura cross coupling reaction of 4-bromoanisole and phenylboronic acid.

Facile synthesis of transition metal containing polyhedral oligomeric silsesquioxane complexes with mesoporous structures and their applications in reducing fire hazards, enhancing mechanical and dielectric properties of epoxy composites

Transition metal (Co or Fe) containing polyhedral oligomeric silsesquioxane complexes (M@POSS-COOH) were prepared from octa carboxyl polyhedral oligomeric silsesquioxane (OC-POSS). The structures of OC-POSS and M@POSS-COOH were characterized by FT-IR, NMR, MALDI-TOF MS and XRD. Fe@POSS-COOH and Co@POSS-COOH possess mesoporous structures, whose Brunauer-Emmett-Teller surface areas (S_BET) are 58.7 m²/g and 46.3 m²/g, respectively. The remaining carboxyl groups of M@POSS-COOH that can react with epoxy groups along with the mesoporous structure increase the network strength of the epoxy resin (EP), and play a significant role in improving the mechanical properties, dielectric properties and thermal properties of the composites. Furthermore, the elemental composition of transition metal and silicon oxygen in the M@POSS-COOH structures significantly increases the amount of char residues of EP composites during the combustion of the material through elements catalysis and surface enrichment, which significantly reduces the toxic smoke density and fire hazards of EP composites. The structural and elemental merits of M@POSS-COOH significantly improve the overall performance of epoxy resin and occupy broad application space.

Post-synthesis modification of functionalised polyhedral oligomeric silsesquioxanes with encapsulated fluoride – enhancing reactivity of T8-F POSS for materials synthesis

The first successful approach for modifying poorly reactive POSS containing F⁻ (T₈-F) and incorporating intact T₈-F within a nanohybrid material is described.

Mono-substituted cage-like silsesquioxanes bound by trifunctional acyl chloride as a multi-donor N,O-type ligand in copper(ii) coordination chemistry: synthesis and structural properties

In this paper, we report on the synthesis of novel copper(ii) complexes containing a multi-donor N,O-type ligand based on mono-substituted cage-like silsesquioxanes bound by trifunctional acyl chloride.

Synthesis and chromatographic evaluation of a new stationary phase based on mild thiol-Michael addition reaction

Click chemistry has attracted increasing attention for the synthesis of novel stationary phases. Considering the advantage of click chemistry, a strategy based on thiol-Michael addition was developed for the preparation of a new stationary phase herein, and a phenyl vinyl sulfone stationary phase (M-PVS) was prepared. The resulting M-PVS bonded silica was characterized by elemental analysis, solid-state ¹³C cross-polarization/magic-angle spinning NMR and infrared spectroscopy, confirming the successful immobilization of phenyl vinyl sulfone on the silica support. The retention properties of M-PVS were investigated and exhibited unambiguous reversed phase retention characteristics. Moreover, shape selectivity and silanol activity were studied to reveal the diverse interactions of M-PVS, including hydrophobic, π-π, hydrogen bonding, and ion-exchange interactions. In addition, de-wetting tolerance and hydrophilic properties were evaluated and a pronounced "U" retention curves were obtained, indicating enhanced retention for polar analytes and transitions of different interaction modes. Selectivity differences between M-PVS column, phenyl column and conventional C₁₈ column were examined using series natural standards. The diverse interactions of M-PVS demonstrated its improved selectivity for the compounds with similar hydrophobic skeleton but different polar substituents.

Synthesis and properties of porous polymers synthesized by Michael addition reactions of multi-functional acrylate, diamine, and dithiol compounds

Porous polymers have been synthesized by Michael addition reactions of multi-functional acrylate and diamine or dithiol compounds. Aza-Michael addition reaction of multi-functional acrylate, trimethylolpropane propoxylate triacrylate (TPT) and hexamethylene diamine (HDA) in dimethyl sulfoxide (DMSO) successfully yielded the porous polymer. The porous structure was characterized by connected globules or co-continuous structure, and could be controlled by the reaction conditions. Mechanical properties of the porous polymers were investigated by compression test. The porous polymers with co-continuous structure showed higher Young's modulus than those with connected globules. The porous polymer absorbed some organic solvents, especially CHCl₃. The porous polymer as prepared in DMSO state showed coloring induced by Christiansen filter effect depending on the reaction time and observation temperature. The thio-Michael addition reaction of TPT and 1,6-hexanedithiol (HDT) in DMSO using different base catalysts also yielded the porous polymer. The porous structure could be controlled by the catalysts amount when the reaction was initiated by a photo-base generator as the base catalyst. The present reaction systems make it possible to synthesize the porous polymers with simple process without phase separator.

Three-dimensional cryogels for biomedical applications

Cryogels are a subset of hydrogels synthesized under sub-zero temperatures: initially solvents undergo active freezing, which causes crystal formation, which is then followed by active melting to create interconnected supermacropores. Cryogels possess several attributes suited for their use as bioscaffolds, including physical resilience, bio-adaptability, and a macroporous architecture. Furthermore, their structure facilitates cellular migration, tissue-ingrowth, and diffusion of solutes, including nano- and micro-particle trafficking, into its supermacropores. Currently, subsets of cryogels made from both natural biopolymers such as gelatin, collagen, laminin, chitosan, silk fibroin, and agarose and/or synthetic biopolymers such as hydroxyethyl methacrylate, poly-vinyl alcohol, and poly(ethylene glycol) have been employed as 3D bioscaffolds. These cryogels have been used for different applications such as cartilage, bone, muscle, nerve, cardiovascular, and lung regeneration. Cryogels have also been used in wound healing, stem cell therapy, and diabetes cellular therapy. In this review, we summarize the synthesis protocol and properties of cryogels, evaluation techniques as well as current in vitro and in vivo cryogel applications. A discussion of the potential benefit of cryogels for future research and their application are also presented.

Hitherto unknown eight-connected frameworks formed from A4B4O12 metal organophosphate heterocubanes

Modulation of a functional group on the distal part of a phosphate ester has been prudently exploited to selectively switch between the formation of D4R SBUs and 3-D framework structures. While amino substitution at the para-position of an aryl phosphate results in the isolation of tetra-amino functionalized discrete D4R zinc phosphate or its 4-connected 3-D framework, the introduction of an acetylamino substituent leads to a single-step assembly of a rare eight-connected 3-D framework solid.

Thiol-ene polymerization for hierarchically porous hybrid materials by adding degradable polycaprolactone for adsorption of bisphenol A

Hierarchically porous materials with multiple pore structures have the potential application in catalysis, separation or bioengineering. A concept was introduced to design and fabricate hierarchically porous hybrid materials (HPHMs) simultaneously containing mesopores and macropores. The proof-of-concept design was demonstrated by fabrication of several kinds of hybrid materials by adding degradable polycaprolactone (PCL) additive, which was simple and easy-operating. The specific surface areas of HPHMs prepared with polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) and 1,4-dithiothreitol (DTT) could reach 727 m²/g by adding 25% PCL additive, while the HPHMs were imperforate prior to degradation of PCL. The characterization further indicated that the macropores could be controlled by the amount of PCL additive. Moreover, the porous properties of HPHMs were influenced by the molecular weight of PCL. Other dithiols compounds were also successful in preparing HPHMs with high specific surface areas over 400 m²/g. Due to hydrophobic interaction and hydrogen bond interaction, the HPHM exhibited good adsorption ability for bisphenol A (BPA) in aqueous solution. Adsorption equilibrium could be achieved within 30 min, and the adsorption capacity was up to 157.4 mg/g. Meanwhile, the removal efficiency was found to be 95.37% for BPA.

Ternary thiol-ene photopolymerization for facile preparation of ionic liquid-functionalized hybrid monolithic columns based on polyhedral oligomeric silsesquioxanes

A simple thiol-ene photopolymerization approach was developed for the rapid preparation of ionic liquid-functionalized hybrid monolithic column based on polyhedral oligomeric silsesquioxane (POSS). "One-pot" polymerization was realized in the UV-transparent fused-silica capillary by using octanethiol, 1-allyl-3-methylimidazolium hexafluorophosphate as functional monomers and methacryl-substituted POSS as a crosslinker. The thiol-vinyl-methacrylate ternary system uniquely exhibits a mixed step-chain growth polymerization regime that combining the thiol-ene reaction and free-radical reaction mechanisms, which provides a simple route to prepare novel POSS-based functionalized hybrid monoliths. The pore property, permeability, and electroosmotic flow (EOF) of the hybrid monoliths can be tailored by proper adjustment of the feeding composition and initiation condition. Morphologic and spectroscopic characterizations of monolithic columns clearly indicate that utilization of the photo-initiated approach in thiol-vinyl polymerization can generate a more homogeneous porous structure, smaller domain size and higher column efficiency (53,800-60,300 plates/m for alkylbenzenes) than the thermally-initiated one (32,800-49,300 plates/m). Significant improvements in mechanical stability, anti-swelling property and tailorability of hybrid polymer were achieved in a simple manner, owing to the photopolymerization of rigid nanoscale POSS units and imidazolium-based ionic liquids in ternary thiol-vinyl system for the first time. The resulting hybrid monolith possessed controllable EOFs at pH values from 2 to 10, and showed a multimode separation mechanism in capillary electrochromatography, including π-π interaction, ion exchange, electrophoretic migration, electrostatic and hydrophobic interaction. Satisfactory separation ability was achieved for the analysis of different types of small molecules.

One-step fabrication of cinchona-based hybrid monolithic chiral stationary phases via photo-initiated thiol-ene polymerization for cLC enantioseparation

Although various click polymerization reactions (thiol-ene, thiol-yne, thiol-Michael, thiol-epoxy and amine-epoxy) have been utilized to prepare either hybrid or organic monolithic columns with homogeneous network structures, there were few reports on fabrication of monolithic CSPs via click polymerization. Herein, a fast and robust approach was explored to fabricate cinchona-based monolithic hybrid CSPs via photo-initiated thiol-ene polymerization within 10 min in one step. A self-synthesized octakis(3-mercaptopropyl) octasilsesquioxane (POSS-SH) was polymerized with phenylisocyanate cinchonidine (PCD) and (+)-N,N'-diallyl-L-tartardiamide (DATDA) or 1,2,4-trivinylcyclohexane (TVCH). The resulting two kinds of as-synthesized monolithic CSPs, poly(POSS-co-DATDA-co-PCD) and poly(POSS-co-TVCH-co-PCD), were evaluated for cLC enantioseparation of acidic racemates. It was found that they exhibited different enantioseparation ability due to using different multivinyl crosslinkers. The influence of ACN content in mobile phase on the enantioseparation of acidic racemates was investigated. The separation mechanism was also discussed on the basis of a comparison of enantioseparation on two kinds of hybrid monolithic CSPs.

Fast fabrication of a hybrid monolithic column containing cyclic and aliphatic hydrophobic ligands via photo-initiated thiol-ene polymerization

Three monomers, octakis (3-mercaptopropyl) octasilsesquioxane, 1,2,4-trivinylcyclohexane and isophytol were employed to synthesize a novel monolithic stationary phase via photo-initiated thiol-ene click polymerization for reversed-phase liquid chromatography. Several factors such as porogenic system, reaction time and the molar ratio of functional groups were investigated in detail. The resulting poly(POSS-co-TVCH-co-isophytol) monolithic column exhibited suitable permeability for fast separation and outstanding thermal stability. Five alkylbenzenes were employed to evaluate the ability of chromatographic separation of the resulting monolithic columns at different flow rates, and showed the highest column efficiencies of 90,200-93,100 N/m (corresponding to 10.4-10.6 μm of plate height) at a velocity of 0.41 mm/s. The baseline separations of five anilines and eight phenols further proved the applicability of poly(POSS-co-TVCH-co-isophytol) monolithic column in the separation of small molecules.

New Polyhedral Oligomeric Silsesquioxanes-Based Fluorescent Ionic Liquids: Synthesis, Self-Assembly and Application in Sensors for Detecting Nitroaromatic Explosives

In this paper, two different models of hybrid ionic liquids (ILs) based on polyhedral oligomeric silsesquioxanes (POSSs) have been prepared. Additionally, these ILs based on POSSs (ILs-POSSs) exhibited excellent thermal stabilities and low glass transition temperatures. ¹H, 13C, and 29Si nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to confirm the structures of the IL-POSSs. Furthermore, the spherical vesicle structures of two IL-POSSs were observed and were caused by self-assembly behaviors. In addition, we found it very meaningful that these two ILs showed lower detection limits of 2.57 × 10-6 and 3.98 × 10-6 mol/L for detecting picric acid (PA). Moreover, the experimental data revealed that the products have high sensitivity for detecting a series of nitroaromatic compounds-including 4-nitrophenol, 2,4-dinitrophenol, and PA-and relatively comprehensive explosive detection in all of the tests of IL-POSSs with nitroaromatic compounds thus far. Additionally, the data indicate that these two new ILs have great potential for the detection of explosives. Therefore, our work may provide new materials including ILs as fluorescent sensors in detecting nitroaromatic explosives.

Fast preparation of hybrid monolithic columns via photo-initiated thiol-yne polymerization for capillary liquid chromatography

Although several approaches have been developed to fabricate hybrid monoliths, it would still take a few hours to finish the formation of monoliths. Herein, photo-initiated thiol-yne polymerization was first adopted to in situ fabricate hybrid monoliths within the confines of UV-transparent fused-silica capillary. A silicon-containing diyne (1,3-diethynyltetramethyl-disiloxane, DYDS) was copolymerized with three multithiols, 1,6-hexanedithiol, trimethylolpropane tris(3-mercaptopropionate) and pentaerythriol tetrakis(3-mercaptopropionate), by using a binary porogenic system of diethylene glycol diethyl ether (DEGDE)/poly(ethylene glycol) (PEG200) within 10 min. Several characterizations of three hybrid monoliths (assigned as I, II and III, respectively) were performed. The results showed that these hybrid monoliths possessed bicontinuous porous structure, which was remarkably different from that via typical free-radical polymerization. The highest column efficiency of 76,000 plates per meter for butylbenzene was obtained on the column I in reversed-phase liquid chromatography (RPLC). It was observed that the efficiencies for strong-retained butylbenzene were almost close to those of weak-retained benzene, indicating a retention-independent efficient performance of small molecules on hybrid column I. The surface area of this hybrid monolith was very small in the dry state (less than 10.0 m²/g), and the chromatographic behavior of hybrid monolithic columns would be possibly explained by radical-mediated step-growth process of thiol-yne polymerization. Finally, the column I was applied for separation of BSA tryptic digest by cLC-MS/MS, indicating satisfactory separation ability for complicated samples.

Synthesis of cubic spherosilicates for self-assembled organic–inorganic biohybrids based on functionalized methacrylates

Covalent hybrid networks created by fully substituted cubic spherosilicates containing functionalized methacrylates as side chains were synthesized.

Facile preparation of multi-functionalized hybrid monoliths via two-step photo-initiated reactions for two-dimensional liquid chromatography-mass spectrometry

A facile approach was developed to prepare hybrid monoliths with different functions via two-step photo-initiated reactions. Firstly, acrylopropyl polyhedral oligomertic silsesquioxane (acryl-POSS) and propargyl acrylate (PA) were used as precursors to synthesize alkynyl-functionalized hybrid monoliths via photo-initiated free radical polymerization. Secondly, the hybrid monoliths were modified with 1-octadecanethiol (ODT) and sodium 3-mercapto-1-propanesulfonate (SMPS) via photo-initiated thiol-yne click reaction to prepare reversed-phase (RP) and strong cation-exchange (SCX) hybrid monoliths, respectively. The results of chromatographic characterization indicated that the column efficiencies for alkylbenzenes on ODT-modified hybrid monolith reached 84,000-87,700 plates per meter at the velocity of 0.58mm/s, and also revealed a retention-independent efficient performance of small molecules in isocratic elution. The SMPS-modified hybrid monolith exhibited both hydrophobicity and ion-exchange mechanisms, and the dynamic binding capacity was calculated to be 1.4×10^-4μmol/cm. Human Hela cells tryptic digest was well separated on ODT-modified hybrid monolith in one-dimensional RPLC-MS/MS, and 2786 unique peptides and 685 proteins were identified. Furthermore, the SMPS-modified monolith coupled with ODT-modified monolith was used for two-dimensional separation of human Hela cells tryptic digest in SCX-RPLC-MS/MS, and the results showed that 9744 unique peptides and 2749 proteins were identified. Compared to those identified in one-dimensional RP system, the total numbers of unique peptides and proteins identified in SCX-RP system increased by 249.7% and 301.3%, respectively.

Tunable Porosity of Cross-Linked-Polyhedral Oligomeric Silsesquioxane Supports for Palladium-Catalyzed Aerobic Alcohol Oxidation in Water

Polyhedral oligomeric silsesquioxane (POSS)-based materials, poly-POSS-T_n [n = 8 (1), 10 (2), 12 (3), and mix (4)], were prepared in high yields via free radical polymerization of corresponding pure forms of methacrylate-functionalized POSS monomers, MMA-POSS-T_n (n = 8, 10, 12), and the mixture form, MMA-POSS-T_mix. Powder X-ray diffraction (XRD) spectra and BET analysis indicate that 1-4 are amorphous materials with high surface areas (683-839 m² g^-1). The surface areas and total pore volumes follow the trend: poly-POSS-T₁₂ > poly-POSS-T₁₀ > poly-POSS-T_mix > poly-POSS-T₈. In addition, on the basis of Barrett-Joyner-Halenda (BJH) analysis, poly-POSS-T₁₂ contains the highest amount of mesopores. The Pd nanoparticles immobilized on poly-POSS-T_n [n = 8 (5), 10 (6), 12 (7), and mix (8)] are well dispersed with 4-6 wt % Pd content and similar average particle sizes of 6.2-6.5 nm, according to transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDX) and microwave plasma-atomic emission spectroscopy (MP-AES). At 90 °C, the stabilized Pd nanoparticles in 5-8 catalyzed aerobic oxidation of benzyl alcohol to benzaldehyde in 72-100% yields at 6 h using a mixture of a H₂O/Pluronic (P123) solution. The PdNp@poly-POSS-T₈ catalyst (5) exhibited the lowest catalytic activity, as a result of its lowest surface areas, total pore volumes, and amounts of mesopores. With the catalyst 8, various benzyl alcohol derivatives were converted to the corresponding aldehydes in good to excellent yields. However, with alcoholic substrates featuring electron-withdrawing substituents, high conversions were achieved with 1 equiv of K₂CO₃ additive and longer reaction times.

Sulfur and Its Role In Modern Materials Science

Although well-known and studied for centuries, sulfur continues to be at the center of an extensive array of scientific research topics. As one of the most abundant elements in the Universe, a major by-product of oil refinery processes, and as a common reaction site within biological systems, research involving sulfur is both broad in scope and incredibly important to our daily lives. Indeed, there has been renewed interest in sulfur-based reactions in just the past ten years. Sulfur research spans the spectrum of topics within the physical sciences including research on improving energy efficiency, environmentally friendly uses for oil refinery waste products, development of polymers with unique optical and mechanical properties, and materials produced for biological applications. This Review focuses on some of the latest exciting ways in which sulfur and sulfur-based reactions are being utilized to produce materials for application in energy, environmental, and other practical areas.

Photochemical radical thiol–ene click-based methodologies for silica and transition metal oxides materials chemical modification: a mini-review

The photochemical radical thiol–ene addition reaction (PRTEA) is a highly powerful synthetic technique for surface modification.