A general route to coat poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) on various substrates and the derived N, P, S-doped hollow carbon shells for catalysis

Design and Piezoelectric Energy Harvesting Properties of a Ferroelectric Cyclophosphazene Salt

Cyclophosphazenes offer a robust and easily modifiable platform for a diverse range of functional systems that have found applications in a wide variety of areas. Herein, for the first time, it reports an organophosphazene-based supramolecular ferroelectric [(PhCH2 NH)6 P3 N3 Me]I, [PMe]I. The compound crystallizes in the polar space group Pc and its thin-film sample exhibits remnant polarization of 5 µC cm-2 . Vector piezoresponse force microscopy (PFM) measurements indicated the presence of multiaxial polarization. Subsequently, flexible composites of [PMe]I are fabricated for piezoelectric energy harvesting applications using thermoplastic polyurethane (TPU) as the matrix. The highest open-circuit voltages of 13.7 V and the maximum power density of 34.60 µW cm-2 are recorded for the poled 20 wt.% [PMe]I/TPU device. To understand the molecular origins of the high performance of [PMe]I-based mechanical energy harvesting devices, piezoelectric charge tensor values are obtained from DFT calculations of the single crystal structure. These indicate that the mechanical stress-induced distortions in the [PMe]I crystals are facilitated by the high flexibility of the layered supramolecular assembly.

Opportunities from Metal Organic Frameworks to Develop Porous Carbons Catalysts Involved in Fine Chemical Synthesis

In the last decade, MOFs have been proposed as precursors of functional porous carbons with enhanced catalytic performances by comparison with other traditional carbonaceous catalysts. This area is rapidly growing mainly because of the great structural diversity of MOFs offering almost infinite possibilities. MOFs can be considered as ideal platforms to prepare porous carbons with highly dispersed metallic species or even single-metal atoms under strictly controlled thermal conditions. This review briefly summarizes synthetic strategies to prepare MOFs and MOF-derived porous carbons. The main focus relies on the application of the MOF-derived porous carbons to fine chemical synthesis. Among the most explored reactions, the oxidation and reduction reactions are highlighted, although some examples of coupling and multicomponent reactions are also presented. However, the application of this type of catalyst in the green synthesis of biologically active heterocyclic compounds through cascade reactions is still a challenge.

Cyclophosphazene Intrinsically Derived Heteroatom (S, N, P, O)-Doped Carbon Nanoplates for Ultrasensitive Monitoring of Dopamine from Chicken Samples

A novel, metal-free electrode based on heteroatom (S, N, P, O)-doped carbon nanoplates (SNPO-CPL) modifying lead pencil graphite (LPG) has been synthesized by carbonizing a unique heteroatom (S, N, P, O)-containing novel polymer, poly(cyclcotriphosphazene-co-2,5-dioxy-1,4-dithiane) (PCD), for precise screening of dopamine (DA). The designed electrode, SNPO-CPL-800, with optimized percentage of S, N, P, O doping through the sp2-carbon chain, and a large number of surface defects (thus leading to a maximum exposition number of catalytic active sites) led to fast molecular diffusion through the micro-porous structure and facilitated strong binding interaction with the targeted molecules in the interactive signaling transducer at the electrode-electrolyte interface. The designed SNPO-CPL-800 electrode exhibited a sensitive and selective response towards DA monitoring, with a limit of detection (LOD) of 0.01 nM. We also monitored DA levels in commercially available chicken samples using the SNPO-CPL-800 electrode even in the presence of interfering species, thus proving the effectiveness of the designed electrode for the precise monitoring of DA in real samples. This research shows there is a strong potential for opening new windows for ultrasensitive DA monitoring with metal-free electrodes.

Pd on cyclotriphosphazen-hexa imine decorated boehmite as an efficient catalyst for hydrogenation of nitro arenes under mild reaction condition

Cyclotriphosphazen-hexa imine ligand was prepared through successive reactions of phosphonitrilchloride trimer with 4-hydroxybenzaldehyde and (3-aminopropyl) triethoxy silane. The as-prepared ligand was then covalently grafted on boehmite to furnish an efficient support for the immobilization of Pd nanoparticles and synthesis of a novel heterogeneous catalyst for hydrogenation of nitro arenes. The catalytic tests revealed that the catalyst had excellent catalytic activity for hydrogenation of various nitro arenes with different steric and electronic features under mild reaction condition in aqueous media. Noteworthy, the catalyst was highly selective and in the substrates with ketone or aldehyde functionalities, reduction of nitro group was only observed. The catalyst was also recyclable and only slight loss of activity was detected after each recycling run. Hot filtration test also approved true heterogeneous nature of catalysis.

Coupled nickel-cobalt nanoparticles/N,P,S-co-doped carbon hybrid nanocages with high performance for catalysis and protein adsorption

Carbon-supported bimetallic NiCo nanoparticles (NPs) have emerged as attractive catalysts and adsorbents for the reduction of 4-nitrophenol (4-NP) and separation of histidine-rich (His-rich) protein recently due to their low cost, high catalytic activity and good affinity for His-rich protein. In this study, new strongly coupled nickel-cobalt alloy/N,P,S co-doped carbon (NPSC) nanocages are rationally designed via chemical etching of the ZIF-67 dodecahedron with Ni²⁺ under sonication at room temperature, followed by poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) coating and subsequent carbonization treatment in a nitrogen atmosphere. When evaluated as a catalyst for 4-NP or an adsorbent for His-rich protein, the as-prepared NiCo@NPSC nanocages obtained at 700 °C show better performance than those obtained at other temperatures (500 and 900 °C). This improved catalytic effect is attributed to the controllable size and fine distribution of the NiCo NPs together with the effective contact between the catalysts and the N,P,S co-doped carbon matrix, leading to a superior catalytic effect on the reduction of 4-NP and the adsorption of His-rich protein. This catalyst design principle can be easily extended to other catalysis research fields.

Encapsulated RuP2-RuS2 nanoheterostructure with regulated interfacial charge redistribution for synergistically boosting hydrogen evolution electrocatalysis

Exploring cost-effective electrocatalysts with suitable hydrogen binding strength and rational micro/nano-architecture towards the hydrogen evolution reaction (HER) is crucial for energy technologies, yet remains a tough challenge. Herein we present the first instance of a nanoscale RuP₂-RuS₂ heterostructure encapsulated in N, P, and S co-doped porous carbon nanosheets (RuP₂-RuS₂/NPS-C) for boosting the HER. The synthesis involves the construction of a 2D core-shell structured precursor in which Ru³⁺-functionalized g-C₃N₄ is wrapped by poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) followed by pyrolysis. In this nanocomposite, the unique architecture with a highly dispersed embedded RuP₂-RuS₂ nanoheterostructure guarantees not only full exposure of the active sites with enhanced robustness but also smooth mass/charge transfer. More significantly, the experimental results and theoretical calculations reveal that coupling RuP₂ with RuS₂ to construct a heterointerface can induce charge redistribution, giving rise to optimized hydrogen adsorption energy for substantially accelerating the HER. This work provides a novel strategy to engineer high-performance Ru-based electrocatalysts by elegantly modulating the micro-/nano-architecture and interface coupling effect.

Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts

The development of cost-effective, efficient, and novel catalytic systems is always an important topic for heterogeneous catalysis from academia and industrial points of view. Heteroatom-doped carbon materials have gained more and more attention as effective heterogeneous catalysts to replace metal-based catalysts, because of their excellent physicochemical properties, outstanding structure characteristics, environmental compatibility, low cost, inexhaustible resources, and low energy consumption. Doping of heteroatoms can tailor the properties of carbons for different utilizations of interest. In comparison to pure carbon catalysts, these catalysts demonstrate superior catalytic activity in many organic reactions. This review highlights the most recent progress in synthetic strategies to fabricate metal-free heteroatom-doped carbon catalysts including single and multiple heteroatom-doped carbons and the catalytic applications of these fascinating materials in various organic transformations such as oxidation, hydrogenation, hydrochlorination, dehydrogenation, etc.

Recent advances in metal-free heteroatom-doped carbon heterogeneous catalysts including the preparation methods and their catalytic applications in various organic reactions have been reported.

Effective Poly (Cyclotriphosphazene-Co-4,4'-Sulfonyldiphenol)@rGO Sheets for Tetracycline Adsorption: Fabrication, Characterization, Adsorption Kinetics and Thermodynamics

The development of excellent drug adsorbents and clarifying the interaction mechanisms between adsorbents and adsorbates are greatly desired for a clean environment. Herein, we report that a reduced graphene oxide modified sheeted polyphosphazene (rGO/poly (cyclotriphosphazene-co-4,4'-sulfonyldiphenol)) defined as PZS on rGO was used to remove the tetracycline (TC) drug from an aqueous solution. Compared to PZS microspheres, the adsorption capacity of sheeted PZS@rGO exhibited a high adsorption capacity of 496 mg/g. The adsorption equilibrium data well obeyed the Langmuir isotherm model, and the kinetics isotherm was fitted to the pseudo-second-order model. Thermodynamic analysis showed that the adsorption of TC was an exothermic, spontaneous process. Furthermore, we highlighted the importance of the surface modification of PZS by the introduction of rGO, which tremendously increased the surface area necessary for high adsorption. Along with high surface area, electrostatic attractions, H-bonding, π-π stacking and Lewis acid-base interactions were involved in the high adsorption capacity of PZS@rGO. Furthermore, we also proposed the mechanism of TC adsorption via PZS@rGO.

Synthesis and characterization of biodegradable and antioxidant phosphazene-tannic acid nanospheres and their utilization as drug carrier material

In this study, hexachlorocyclotriphosphazene (HCCP) and tannic acid (TA) were used at different stoichiometric ratios to synthesize cyclomatrix-type polymeric materials with different surface features and dimensions. Using different reactive ratios, the structure and surface functional groups of the synthesized polymeric particles were explained using Fourier-Transform Infrared Spectroscopic (FTIR), Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric (TG) analysis techniques. With morphologically fully spherical structure and mean 234.82 ± 49.37 nm dimensions, Phz-TA (4:1) nanospheres were researched for in vitro biodegradability, antioxidant features, and usability as a drug release system. In vitro biodegradability of Phz-TA (4:1) nanospheres was investigated at pH = 7.0 and pH = 1.2. Determined to degrade in 8-10 h at these pH values, nanospheres were used for releasing of Rhodamine 6G as a model drug. Due to the rich phenolic structure of the contained tannic acid units, nanospheres were determined to simultaneously have antioxidant features. Thus, this study determined that Phz-TA nanospheres with in vitro biodegradability and antioxidant features are promising polymeric materials for use as a potential drug-carrier in the future.

Charge Redistribution Caused by S,P Synergistically Active Ru Endows an Ultrahigh Hydrogen Evolution Activity of S-Doped RuP Embedded in N,P,S-Doped Carbon

Water splitting for production of hydrogen as a clean energy alternative to fossil fuel has received much attention, but it is still a tough challenge to synthesize electrocatalysts with controllable bonding and charge distribution. In this work, ultrafine S-doped RuP nanoparticles homogeneously embedded in a N, P, and S-codoped carbon sheet (S-RuP@NPSC) is synthesized by pyrolysis of poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) as the source of C/N/S/P. The bondings between Ru and N, P, S in PZS are regulated to synthesize RuS2 (800 °C) and S-RuP (900 °C) by different calcination temperatures. The S-RuP@NPSC with low Ru loading of 0.8 wt% with abundant active catalytic sites possesses high utilization of Ru, the mass catalytic activity is 22.88 times than 20 wt% Pt/C with the overpotential of 250 mV. Density functional theory calculation confirms that the surface Ru (-0.18 eV) and P (0.05 eV) are catalytic active sites for the hydrogen evolution reaction (HER), and the according charge redistribution of Ru is regulated by S and P with reverse electronegativity and electron-donor property to induce a synergistically enhanced reactivity toward the HER. This work provides a rational method to regulate the bonding and charge distribution of Ru-based electrocatalysts by reacting macromolecules with multielement of C/N/S/P with Ru.

N-Doped carbon nanofibers derived from bacterial cellulose as an excellent metal-free catalyst for selective oxidation of arylalkanes

N-Doped carbon nanofibers derived from one-step pyrolysis of low-cost bacterial cellulose with the assistance of urea were an excellent metal-free carbocatalyst for selective oxidation of arylalkanes.

Facile fabrication of Cu-based alloy nanoparticles encapsulated within hollow octahedral N-doped porous carbon for selective oxidation of hydrocarbons

HKUST-1 serves as a template for an imidazolium-based ionic polymer; anion exchange and subsequent topotactic transformation generate hollow nitrogen-doped porous carbon incorporated with Cu-based alloy nanoparticles.

Hollow carbon materials with versatile chemical compositions and complicated shell architectures hold great promise in heterogeneous catalysis. However, it is a daunting challenge to synthesize metal alloy nanoparticles (NPs) supported by hollow nanostructures. Herein, we present a simple approach for facile fabrication of Pd–Cu alloy NPs embedded in hollow octahedral N-doped porous carbon (Pd–Cu@HO-NPC). The hollow material is derived from HKUST-1 coated by an imidazolium-based ionic polymer (ImIP). Water-sensitive HKUST-1 is simultaneously removed in the process of anion exchange between bromide in the ImIP shell and tetrachloropalladate in aqueous medium. The released Cu(ii) ions and exchanged Pd(ii) ions serve as Cu and Pd sources in the subsequent pyrolysis. The resultant Pd–Cu@HO-NPC exhibits high catalytic activity, selectivity, stability and recyclability in the aerobic oxidation of hydrocarbons. More attractively, the synthetic strategy is of excellent generality, and could be extended to the synthesis of Cu-based bimetallic and trimetallic alloy NPs, such as Pt–Cu@HO-NPC and Pd–Pt–Cu@HO-NPC. This work highlights the superiority of water-sensitive metal–organic frameworks in the ingenious design of hollow carbon materials incorporated with well-dispersed metal alloy NPs.

Controllable Synthesis of Multiheteroatoms Co-Doped Hierarchical Porous Carbon Spheres as an Ideal Catalysis Platform

The synthesis of porous carbon spheres with hierarchical porous structures coupled with the doping of heteroatoms is particularly important for advanced applications. In this research, a new route for efficient and controllable synthesis of hierarchical porous carbon spheres co-doped with nitrogen, phosphorus, and sulfur (denoted as NPS-HPCs) was reported. This new approach combines in situ polymerization of hexachlorocyclophosphazene and 4,4'-sulfonyldiphenol with the self-assembly of colloidal silica nanoparticles (SiO₂ NPs). After pyrolysis and subsequent removal of the SiO₂ NPs, the resulting NPS-HPCs possess a high surface area (960 m²/g) as well as homogeneously distributed N, P, and S heteroatoms. The NPS-HPCs are shown to be an ideal support for anchoring highly dispersed and uniformly sized noble metal NPs for heterogeneous catalysis. As a proof of concept, Pd NPs are loaded onto the NPS-HPCs using only methanol as a reductant at room temperature. The prepared Pd/NPS-HPCs are shown to exhibit high activity, excellent stability, and recyclability for hydrogenation of nitroarenes.