Triphenylamine-Functionalized Silsesquioxane-Based Hybrid Porous Polymers: Tunable Porosity and Luminescence for Multianalyte Detection

Porous organic polymers (POPs) for environmental remediation

Modern global industrialization along with the ever-increasing growth of the population has resulted in continuous enhancement in the discharge and accumulation of various toxic and hazardous chemicals in the environment. These harmful pollutants, including toxic gases, inorganic heavy metal ions, anthropogenic waste, persistent organic pollutants, toxic dyes, pharmaceuticals, volatile organic compounds, etc., are destroying the ecological balance of the environment. Therefore, systematic monitoring and effective remediation of these toxic pollutants either by adsorptive removal or by catalytic degradation are of great significance. From this viewpoint, porous organic polymers (POPs), being two- or three-dimensional polymeric materials, constructed from small organic molecules connected with rigid covalent bonds have come forth as a promising platform toward various leading applications, especially for efficient environmental remediation. Their unique chemical and structural features including high stability, tunable pore functionalization, and large surface area have boosted the transformation of POPs into various macro-physical forms such as thick and thin-film membranes, which led to a new direction in advanced level pollutant removal, separation and catalytic degradation. In this review, our focus is to highlight the recent progress and achievements in the strategic design, synthesis, architectural-engineering and applications of POPs and their composite materials toward environmental remediation. Several strategies to improve the adsorption efficiency and catalytic degradation performance along with the in-depth interaction mechanism of POP-based materials have been systematically summarized. In addition, evolution of POPs from regular powder form application to rapid and more efficient size and chemo-selective, "real-time" applicable membrane-based application has been further highlighted. Finally, we put forward our perspective on the challenges and opportunities of these materials toward real-world implementation and future prospects in next generation remediation technology.

Triphenylbenzene functionalized polyhedral oligomeric silsesquioxane fluorescence sensor for the selective analysis of trace nitrofurazone in aquatic product and cosmetics

Nitrofurazone (NFZ) is carcinogenic and mutagenic to human in long-term ingestion, and it is prohibited to be added in food. In this work, a novel triphenylbenzene (TPB) functionalized fluorescent hybrid porous polymers (POSS@TPB) was constructed by using polyhedral oligomeric silsesquioxane (POSS) as the rigid group and TPB as the core unit of high fluorescence. The morphology and physicochemical properties of POSS@TPB were characterized in detail. Moreover, the synergistic effect of inner filter effect and photoinduced electron transfer is verified by experimental and simulation results. After condition optimization, a NFZ analysis method based on POSS@TPB probe was established with a linear range of 0.4-16.5 mg/L and a detection limit of 0.13 mg/L. In addition, the fluorescent probe has good stability, anti-interference and considerable reusability. At the same time, the selective analysis of trace NFZ in aquatic product and cosmetics was carried out with satisfied recoveries of 87%-110.6% and relative standard deviation less than 4.1%. And the results were verified by high-performance liquid chromatography method. Overall, this fluorescence sensor has excellent performance in NFZ analysis, which provides a broad application prospect for the repeatable and selective residue NFZ analysis in aquatic product and cosmetics.

Porous organic polymers as a platform for sensing applications

Sensing analysis is significantly important for human health and environmental safety, and has gained increasing concern. As a promising material, porous organic polymers (POPs) have drawn widespread attention due to the availability of plentiful building blocks and their tunable structures, porosity and functions. Moreover, the permanent porous nature could provide a micro-environment to interact with guest molecules, rendering POPs attractive for application in the sensing field. In this review, we give a comprehensive overview of POPs as a platform for sensing applications. POP-based sensors are mainly divided into five categories, including fluorescence turn-on sensors, fluorescence turn-off sensors, ratiometric fluorescent sensors, colorimetric sensors and chemiresistive sensors, and their various sensing applications in detecting explosives, metal ions, anions, small molecules, biological molecules, pH changes, enantiomers, latent fingerprints and thermosensation are summarized. The different structure-based POPs and their corresponding synthetic strategies as well as the related sensing mechanisms mainly including energy transfer, donor-acceptor electron transfer, absorption competition quenching and inner filter effect are also involved in the discussion. Finally, the future outlook and perspective are addressed briefly.

Micro-/Mesoporous Fluorescent Polymers and Devices for Visual Pesticide Detection with Portability, High Sensitivity, and Ultrafast Response

The residue of pesticides in crops, soil, and water continues to be a widespread concern due to the threat to human health and food safety. With the aim to develop highly sensitive sensing materials and portable detection devices, two dicarbazole-based fluorescent micro-/mesoporous polymers (JYs) with a larger specific surface area and pore sizes ranging from 1.1 to 34.2 nm are synthesized. The Stern-Volmer constants of JY fluorescence quenching for imidacloprid (50,063 M^-1) exceed 23-51 times those of the reported porous organic polymers (980-2173 M^-1). Of particular interest is the observation that JYs show rapid fluorescence response (2 s) and ultralow detection limit (30 ppb) for imidacloprid in water medium. The pronounced chemsensing property is attributed to the synergistic role of the hierarchical pore structure, large π-conjugation of chromophore groups, and strong inner filter effect between the polymer and imidacloprid molecule. Moreover, the pesticide detection of JYs exhibits good interference resistance in complicated service environments such as the extract liquids of the apple peel and field soil as well as aqueous solutions of various cations and anions. Because of the portability, excellent reusability, and sensitive fluorescence response, the prepared JYs and detection devices have promising applications in the on-site monitoring and early warning of the pesticide residues.

POSS and imidazolium-constructed ionic porous hypercrosslinked polymers with multiple active sites for synergistic catalytic CO2 transformation

In this work, we reported a facile one-pot approach to construct polyhedral oligomeric silsesquioxane (POSS) and imidazolium-based ionic porous hypercrosslinked polymers (denoted as iPHCPs) with multiple active sites towards efficient catalytic conversion of carbon dioxide (CO₂) to high value-added cyclic carbonates. The targeted iPHCPs were synthesized from a rigid molecular building block octavinylsilsesquioxane (VPOSS) and a newly-designed phenyl-based imidazolium ionic crosslinker through the AlCl₃-catalyzed Friedel-Crafts reaction. The desired multiple active sites come from the mixed anions including free Cl^- and Br^- anions, and in situ formed Lewis acidic metal-halogen complex anions [AlCl₃Br]^- within imidazolium moieties and POSS-derived Si-OH groups during the synthetic process. The typical polymer iPHCP-12 possesses a hierarchical micro-/mesoporous structure with a high surface area up to 537 m² g^-1 and shows a fluffy nano-morphology. By virtue of the co-existence of free nucleophilic Cl^- and Br^- anions, the metal complex anion [AlCl₃Br]^- with both electrophilic and nucleophilic characters and electrophilic hydrogen bond donor (HBD) Si-OH groups, iPHCP-12 is regarded as an efficient recyclable heterogeneous catalyst for synergistic catalytic conversion of CO₂ with various epoxides into cyclic carbonates under mild conditions. The present work provides a succinct one-pot strategy to construct task-specific ionic porous hypercrosslinked polymers from easily available modules for the targeted catalytic applications.

Multifunctional chiral cationic porous organic polymers: gas uptake and heterogeneous asymmetric organocatalysis

Chiral porous organic polymers are characterized by robust, non-toxic and recyclable properties. Therefore, compared with small molecular catalysts, they have attracted much attention in the field of heterogeneous asymmetric organic catalysis.

Cage-like silsesquioxanes-based hybrid materials

Cage-like silsesquioxanes are considered to be ideal and versatile building blocks of hybrid materials due to their unique structures and excellent performance. This Perspective highlights recent advances in the field of cage-like silsesquioxane-based hybrid materials, ranging from monomer functionalization and materials preparation to application. The existing issues are reviewed and the challenges and prospects in this field are also discussed for further development and exploitation.

Creation of Carbazole-Based Fluorescent Porous Polymers for Recognition and Detection of Various Pesticides in Water

The development of sensitive, fast, and portable methods for detecting the residual toxic pesticides is essentially important because of the increasing concerns for public health and safety. For this purpose, three fluorescent porous organic polymers containing pendant N-benzyl carbazole, N-benzyl dibromo-carbazole, and N-benzyl dimethoxy-carbazole groups were synthesized via a one-step polymerization reaction. The resultant polymers emit bright cyan, blue, and green light under the ultraviolet lamp, respectively, with the Brunauer-Emmett-Teller area up to 858 m² g^-1 and tunable pore sizes in the range of 0.5-36 nm. Six pesticides including trifluralin, isopropalin, glyphosate, fenitrothion, imidacloprid, and cyfluothrin are selected as the analytes to investigate the recognition and detection ability of polymers in terms of the different photo-physical properties of polymers, chemical structure of organic pesticides as well as the pore sizes of polymers, and molecular sizes of pesticides. It is interesting to find that, even though in water medium, the measured fluorescent quenching Stern-Volmer coefficient for trifluralin still reaches 26,040 L mol^-1 and is nearly unchanged under both acidic or basic service conditions. Moreover, the test paper prepared from the polymer exhibits a rapid fluorescent response when contacting the aqueous trifluralin dispersion liquid, and the sensitivity remains stable after recycling use for twelve times.

Flexible Cyclosiloxane-Linked Fluorescent Porous Polymers for Multifunctional Chemical Sensors

The construction of porous polymers linked by flexible building units has been considered a great challenge. Here, we address this challenge by using flexible 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxanes to react with brominated pyrene, tetraphenylethene, and spirobifluorene via the Heck reaction, resulting in three cyclosiloxane-linked fluorescent porous polymers. The materials exhibit high porosity, strong fluorescence, and tunable emission colors. Such properties impart the promise of these polymers as candidates for multifunctional chemical sensors to identify latent fingerprints with a strong anti-interference ability under actual conditions (e.g., rainy environment) and to detect nitroaromatic explosives and metal ions, especially 2,4,6-trinitrotoluene or picric acid, and the Fe³⁺ ion, with low limits of detection and a high selectivity. Moreover, a paper sensor was further developed and is found to be sensitive to the solution, solid, and vapor phases of explosives and the Fe³⁺ ion, complete with a rapid response time and visual detection. These results may open up new horizons for exploring porous polymers, particularly those with a strong fluorescence, based on flexible linkers.

Diphenylphosphine-Substituted Ferrocene/Silsesquioxane-Based Hybrid Porous Polymers as Highly Efficient Adsorbents for Water Treatment

The study describes the synthesis of two porous hybrid polymers (abbreviated as DPPF-HPP and DPPOF-HPP) from the Friedel-Crafts reaction of octavinylsilsesquioxane with 1,1'-bis(diphenylphosphine)ferrocene (DPPF) and 1,1'-bis(diphenylphosphine oxide)ferrocene (DPPOF), respectively. DPPF-HPP and DPPOF-HPP possess surface areas of about 890 and 780 m² g^-1, respectively, as well as similar pore structures of the coexisting micropores and mesopores. They are excellent materials for high adsorption of different dyes with adsorption capacities of 2280 mg g^-1 for Congo Red and 1440 mg g^-1 for Crystal Violet. DPPF-HPP also shows a strong affinity to adsorb Hg²⁺ ions (300 mg g^-1). These materials show no sign of degradation under repeated cycles and thus offer potential for wastewater treatment.

A Highly Effective Route to Si-O-Si Moieties through O-Silylation of Silanols and Polyhedral Oligomeric Silsesquioxane Silanols with Disilazanes

A simple and highly practical catalyst-free O-silylation of silanols with commercially available disilazanes has been developed under mild conditions. In the case of polyhedral oligomeric silsesquioxane (POSS) silanols and some other silanols, it was necessary to use catalytic amounts of inexpensive Bi(OTf)₃ as additional catalyst. This efficient chlorine-free protocol involves the synthesis of a wide range of important organosilicon derivatives such as unsymmetrical disiloxanes and functionalized silsesquioxanes.

Cost-effective preparation of microporous polymers from formamide derivatives and adsorption of CO2 under dry and humid conditions

Nitrogen-rich microporous polymers are prepared via a catalyst-free polymerization reaction using formamide derivatives as monomers, which exhibit outstandingly high CO₂/N₂ selectivity up to 151 and 173 at 273 K under dry and humid conditions, respectively.

Fluorescent porous organic polymers

Porous organic polymers (POPs), which are built from pure organic building blocks through strong covalent bonds, are intriguing platforms with multiple functionalities.

Copper(ii) triflate-mediated synthesis of functionalized silsesquioxanes via dehydrogenative coupling of POSS silanols with hydrosilanes

In light of the fact that the design of new catalytic routes leading to functionalized silsesquioxanes is currently of high relevance; herein we report a novel, highly effective and convenient catalytic approach for the modification of silsesquioxanes. We present a dehydrogenative coupling reaction of completely as well as incompletely condensed POSS silanols with a wide range of commercially available hydrosilanes mediated by inexpensive copper(ii) trifluoromethanesulfonate. This research also includes mechanistic studies for this process.

Fluorescent electronic tongue based on soluble conjugated polymeric nanoparticles for the discrimination of heavy metal ions in aqueous solution

A fluorescence sensing array (or fluorescent electronic tongue) based on six sorts of soluble conjugated polymeric nanoparticles (SCPNs) decorated with PEG chains is designed for the rapid identification of heavy metal ions in water.

Siloxane-Based Nanoporous Polymers with Narrow Pore-size Distribution for Cell Imaging and Explosive Detection

Porous polymers are among the most promising porous materials for various application because they show the combined advantages of fluorescent porous materials and polymers. This study developed a cell imaging technique based on luminescent porous organosilicon polymers (LPOPs) that were synthesized via Friedel-Crafts reaction of octaphenylcyclotetrasiloxane with octavinylsilsesquioxanes. The porous organosilicon polymers possessed narrow pore-size distribution, high surface area, and monomodal nanopores centered at approximately 0.59 nm. The excellent properties to the porous polymers can be attributed to the fine structures of LPOPs. LPOP-2 owned the highest fluorescence intensity and micropore volume ratio in LPOPs and showed high selectivity for Fe³⁺ detection and excellent sensitivity to nitroaromatic compound detection. Interestingly, these porous polymers still exhibited excellent responsiveness to Fe³⁺ ion even when inside of living cells. We also fabricated a paper-based sensor using LPOP-2 to develop a simple method for visual detection of explosives. This rapid and visual paper sensor demonstrates promising application for explosive detection and can be expanded for the detection of other analytes.

Introduction of Boron Functionalities into Silsesquioxanes: Novel Independent Methodologies

Owing to their versatile application possibilities, silsesquioxanes (SQs) are of considerable interest for creating hybrid inorganic-organic materials. In this report, two novel and independent strategies for the direct attachment of boron functionalities to silsesquioxanes are presented. Encouraged by our previous work concerning the synthesis of borasiloxanes through the catalyst-free dehydrogenative coupling of silanols and boranes, we decided to apply our method to a synthesis of various boron-functionalized silsesquioxanes. During our tests, we also investigated the activity of scandium(III) triflate, which we have previously used as an excellent catalyst for the obtaining of Si-O-Si and Si-O-Ge moieties. As a result, we also discovered a novel approach for the O-borylation of Si-OH groups in silsesquioxanes with allylborane. Both routes are highly chemoselective and efficiently lead to the obtaining of Si-O-B moiety under air atmosphere and at room temperature.

Constructing POSS and viologen-linked porous cationic frameworks induced by the Zincke reaction for efficient CO2 capture and conversion

POSS and viologen-linked porous cationic frameworks were constructed via the Zincke reaction towards efficient CO₂ capture and conversion under ambient conditions.