Metal-Free Boron-Containing Heterogeneous Catalysts

Hydroxyl-Bonded Co Single Atom Site on Boroncarbonitride Surface Realizes Nonsacrificial H2O2 Synthesis in the Near-Infrared Region

Photocatalytic synthesis of hydrogen peroxide (H2O2) from O2 and H2O under near-infrared light is a sustainable renewable energy production strategy, but challenging reaction. The bottleneck of this reaction lies in the regulation of O2 reduction path by photocatalyst. Herein, the center of the one-step two-electron reduction (OSR) pathway of O2 for H2O2 evolution via the formation of the hydroxyl-bonded Co single-atom sites on boroncarbonitride surface (BCN-OH2/Co1) is constructed. The experimental and theoretical prediction results confirm that the hydroxyl group on the surface and the electronic band structure of BCN-OH2/Co1 are the key factor in regulating the O2 reduction pathway. In addition, the hydroxyl-bonded Co single-atom sites can further enrich O2 molecules with more electrons, which can avoid the one-electron reduction of O2 to •O2 -, thus promoting the direct two-electron activation hydrogenation of O2. Consequently, BCN-OH2/Co1 exhibits a high H2O2 evolution apparent quantum efficiency of 0.8% at 850 nm, better than most of the previously reported photocatalysts. This study reveals an important reaction pathway for the generation of H2O2, emphasizing that precise control of the active site structure of the photocatalyst is essential for achieving efficient conversion of solar-to-chemical.

Investigating the Catalytic Influence of Boron on Ni-Co/Ca Catalysts for Improved Syngas Generation from Rice Straw Pyrolysis

A series of boron-promoted Ni-Co/Ca catalysts were synthesized by the sol-gel method to enhance syngas generation from biomass pyrolysis. The efficiency of these catalysts was evaluated during the pyrolysis of rice straw in a fixed-bed reactor, varying the Ni/Co ratio, boron addition, calcination temperature, and residence time. The catalysts underwent comprehensive characterization using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), and hydrogen temperature-programmed reduction (H2-TPR). The results indicated that the Ni-Co/Ca catalysts yielded superior syngas compared to singular Ni or Co catalysts, suggesting a synergistic interplay between nickel and cobalt. The incorporation of 4% boron significantly decreased the particle size of the active metals, enhancing both the catalytic activity and stability. Optimal syngas production was achieved under the following conditions: a biomass-to-catalyst mass ratio of 2:1, a Ni-Co ratio of 1:1, a calcination temperature of 400 °C, a pyrolysis temperature of 800 °C, and a 20 min residence time. These conditions led to a syngas yield of 431.8 mL/g, a 131.28% increase over the non-catalytic pyrolysis yield of 188.6 mL/g. This study not only demonstrates the potential of Ni-Co/Ca catalysts in biomass pyrolysis for syngas production but also provides a foundation for future catalyst performance optimization.

Cu-Catalyzed Divergent Transformations of Allenylethylene Carbonates with Diboron Reagents

Divergent transformations of allenylethylene carbonates with diboron reagents catalyzed by copper are disclosed. By using CuCl/IPr·HCl as the catalyst, the allenylethylene carbonates react with B2hex2 to afford 2,4-dien-1-ols as the product in the presence of Cs2CO3 as the base, iPrOH as the additive, and 1,4-dioxane as the solvent. And they react with B2pin2 to form boronic half acids in the presence of NaOtBu as the base, water as the additive, and THF as the solvent. The reactions afford corresponding products in good stereoselectivities and yields, and further derivatizations of boronic half acids and study of the mechanism are also demonstrated.

Metal-Free Heterogeneous Photocatalysis for Carbocarboxylation of Alkenes: Efficient Synthesis of γ-Amino Carboxylic Derivatives

A metal-free heterogeneous protocol is established herein for the synthesis of value-added γ-amino acid scaffolds via carbocarboxylation of alkenes with CO2 and alkylamines under visible light irradiation. The protocol shows broad substrate scope under mild reaction conditions and good stability of the catalyst for recycle tests. Moreover, the methodology could be feasible to the late-stage derivatization of several natural products, enriching the chemical arsenal for practical application.

A metal-free photoactive nitrogen-doped carbon nanosolenoid with broad absorption in visible region for efficient photocatalysis

Riemann surfaces inspired chemists to design and synthesize such multidimensional curved carbon architectures. It has been predicted that carbon nanosolenoid materials with Riemann surfaces have unique structures and novel physical properties. Here we report the first synthesis of a nitrogen-doped carbon nanosolenoid (N-CNS) using bottom-up approach with a well-defined structure. N-CNS was obtained by a rational Suzuki polymerization, followed by oxidative cyclodehydrogenation. The successful synthesis of N-CNS was fully characterized by GPC, FTIR, solid-state 13C NMR and Raman techniques. The intrinsic single-strand molecular structures of N-CNS helices can be clearly resolved using low-dose integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM) technique. Possessing unique structural and physical properties, this long π-extended polymer N-CNS can provide new insight towards bottom-up syntheses of curved nanoribbons and potential applications as a metal-free photocatalyst for visible-light-driven H2 evolution and highly efficient photocatalyst for photoredox organic transformations.

Balancing Mass Transfer and Active Sites to Improve Electrocatalytic Oxygen Reduction by B,N Codoped C Nanoreactors

Mass transfer is critical in catalytic processes, especially when the reactions are facilitated by nanostructured catalysts. Strong efforts have been devoted to improving the efficacy and quantity of active sites, but often, mass transfer has not been well studied. Herein, we demonstrate the importance of mass transfer in the electrocatalytic oxygen reduction reaction (ORR) by tailoring the pore sizes. Using a confined-etching strategy, we fabricate boron- and nitrogen-doped carbon (B,N@C) electrocatalysts featuring abundant active sites but different porous structures. The ORR performance of these catalysts is found to correlate with diffusion of the reactant. The optimized B,N@C with trimodal-porous structures feature enhanced O₂ diffusion and better activity per heteroatomic site toward the ORR process. This work demonstrates the significance of the nanoarchitecture engineering of catalysts and sheds light on how to optimize structures featuring abundant active sites and enhanced mass transfer.

Highly efficient metal-free borocarbonitride catalysts for electrochemical reduction of N2 to NH3

The electrocatalytic nitrogen reduction reaction (NRR) for ammonia (NH₃) under ambient conditions is emerging as a potentially sustainable alternative to the traditional, energy-intensive Haber-Bosch process for ammonia production. Currently, metal-based electrocatalysts constitute the majority of reported NRR catalysts. However, they often suffer from the shortcomings of competitive reactions of nitrogen adsorption/activation and hydrogen generation. Therefore, there is an urgent need to develop more environmentally friendly, low energy consumption, and non-polluting high-performance metal-free electrocatalysts. In this study, borocarbonitride (BCN) materials derived from boron imidazolate framework (BIF-20) were used to boost efficient electrochemical nitrogen conversion to ammonia under ambient conditions. The BCN catalyst demonstrated excellent performance in 0.1 M KOH, with an ammonia yield of 21.62 μg h^-1 mg_cat^-1 and a Faradaic efficiency of 9.88% at -0.3 V (Reversible Hydrogen Electrode, RHE). This performance is superior to most metal-free catalysts and even some metal catalysts for NRR. The ¹⁵N₂/¹⁴N₂ isotope labeling experiments and density functional theory (DFT) calculations showed that N₂ can be adsorbed and converted to NH₃ on the surface of BCN, and that the energy barrier can be significantly reduced by structural design for BCN. This work highlights the important role played by the presence of Lewis acid-base pairs in metal-free catalysts for enhancing electrochemical NRR performance.

Hexagonal-borocarbonitride (h-BCN) based heterostructure photocatalyst for energy and environmental applications: A review

Formulation of heterojunction with remarkable high efficiency by utilizing solar light is promising to synchronously overcome energy and environmental crises. In this concern, hexagonal-borocarbonitride (h-BCN) based Z-schemes have proved potential candidates due to their spatially separated oxidation and reduction sites, robust light-harvesting ability, high charge pair migration and separation, and strong redox ability. H-BCN has emerged as a hotspot in the research field as a metal-free photocatalyst with a tunable bandgap range of 0-5.5 eV. The BCN photocatalyst displayed synergistic benefits of both graphene and boron nitride. Herein, the review demonstrates the current state-of-the-art in the Z-scheme photocatalytic application with a special emphasis on the predominant features of their photoactivity. Initially, fundamental aspects and various synthesis techniques are discussed, including thermal polymerization, template-assisted, and template-free methods. Afterward, the reaction mechanism of direct Z-scheme photocatalysts and indirect Z-scheme (all-solid-state) are highlighted. Moreover, the emerging Step-scheme (S-scheme) systems are briefly deliberated to understand the charge transfer pathway mechanism with an induced internal electric field. This review critically aims to comprehensively summarize the photo-redox applications of various h-BCN-based heterojunction photocatalysts including CO₂ photoreduction, H₂ evolution, and pollutants degradation. Finally, some challenges and future direction of h-BCN-based Z-scheme photocatalyst in environmental remediation are also proposed.

Green synthesis of propylene oxide directly from propane

The chemical industry faces the challenge of bringing emissions of climate-damaging CO₂ to zero. However, the synthesis of important intermediates, such as olefins or epoxides, is still associated with the release of large amounts of greenhouse gases. This is due to both a high energy input for many process steps and insufficient selectivity of the underlying catalyzed reactions. Surprisingly, we find that in the oxidation of propane at elevated temperature over apparently inert materials such as boron nitride and silicon dioxide not only propylene but also significant amounts of propylene oxide are formed, with unexpectedly small amounts of CO₂. Process simulations reveal that the combined synthesis of these two important chemical building blocks is technologically feasible. Our discovery leads the ways towards an environmentally friendly production of propylene oxide and propylene in one step. We demonstrate that complex catalyst development is not necessary for this reaction.

In-situ synthesis of non-phase-separated boron carbon nitride for photocatalytic reduction of CO2

Non-phase-separated hexagonal boron carbon nitride (h-BCN) is an emerging type of promising metal-free photocatalyst, but the synthesis of this material remains quite challenging. Here, h-BCN without phase separation was obtained through a novel organic-inorganic hybrid precursor pyrolysis method using boric acid and ethylenediamine as raw materials. The resultant BCN-1 exhibited excellent photocatalytic activity for CO₂ reduction, as confirmed by a CO generation rate of 13.97 μmol g^-1 h^-1 under visible light illumination with no co-catalyst or sacrificial agent. This rate was 9.4 times higher than that of g-C₃N₄ (2.1 μmol g^-1 h^-1) under the same experimental condition. The pre-existing C-N-B bond is essential for mediating the growth kinetics and diminishing the thermodynamically preferred C and BN phase-segregation structure, while ammonia is crucial for C-N-B bond fixation and pore formation during the pyrolysis process. This finding of a facile method for synthesizing non-phase-separated BCN has positive effects on the study of photocatalytic CO₂ reduction by sustainable metal-free catalysts.

COF-5/CoAl-LDH Nanocomposite Heterojunction for Enhanced Visible-Light-Driven CO2 Reduction

Photocatalytic conversion of CO₂ into value-added chemical fuels is an attractive route to mitigate global warming and the energy crisis. Reasonable design of optical properties and electronic behavior of the photocatalyst are essential to improve their catalytic activity. Herein, the 1D/2D heterojunction by direct in-situ synthesis of the covalent organic framework (COF)-5 colloid on the surface of CoAl layered double hydroxide (LDH) was used as the prospective photocatalyst for CO₂ reduction. COF-5/CoAl-LDH nanocomposite achieved 265.4 μmol g^-1 of CO with 94.6 % selectivity over CH₄ evolution in 5 h under visible light irradiation, which was 4.8 and 2.3 times higher than those of COF-5 colloid and CoAl-LDH, respectively. The enhanced catalytic activity was derived from the increased visible-light activity and the construction of type II-2 heterojunction, which greatly optimized visible light harvesting and accelerated the efficient separation of the photoinduced holes and electrons. This work paves the way for rational design of heterojunction catalysts in photocatalytic CO₂ reduction.

Semiconducting Polymers for Oxygen Evolution Reaction under Light Illumination

Sunlight-driven water splitting to produce hydrogen fuel has stimulated intensive scientific interest, as this technology has the potential to revolutionize fossil fuel-based energy systems in modern society. The oxygen evolution reaction (OER) determines the performance of overall water splitting owing to its sluggish kinetics with multielectron transfer processing. Polymeric photocatalysts have recently been developed for the OER, and substantial progress has been realized in this emerging research field. In this Review, the focus is on the photocatalytic technologies and materials of polymeric photocatalysts for the OER. Two practical systems, namely, particle suspension systems and film-based photoelectrochemical systems, form two main sections. The concept is reviewed in terms of thermodynamics and kinetics, and polymeric photocatalysts are discussed based on three key characteristics, namely, light absorption, charge separation and transfer, and surface oxidation reactions. A satisfactory OER performance by polymeric photocatalysts will eventually offer a platform to achieve overall water splitting and other advanced applications in a cost-effective, sustainable, and renewable manner using solar energy.

High-performance potassium poly(heptazine imide) films for photoelectrochemical water splitting

Potassium poly(heptazine imide) photoanode is synthesized, and owing to the improved crystallinity, it has presented a remarkable performance for solar-driven water splitting.

Understanding Single-Atom Catalysis in View of Theory

In the past decade, isolated single atoms have been successfully dispersed on various substrates, with their potential applications being intensively investigated in different reactions. While the essential target of research in single-atom catalysis is the precise synthesis of stable single-atom catalysts (SACs) with clear configurations and impressive catalytic performance, theoretical investigations have also played important roles in identifying active sites, revealing catalytic mechanisms, and establishing structure-activity relationships. Nevertheless, special attention should still be paid in theoretical works to the particularity of SACs. In this Perspective, we will summarize the theoretical progress made on the understanding of the rich phenomena in single-atom catalysis. We focus on the determination of local structures of SACs via comparison between experiments and simulations, the discovery of distinctive catalytic mechanisms induced by multiadsorption, synergetic effects, and dynamic evolutions, to name a few, the proposal of criteria for theoretically designing SACs, and the extension of original concepts of single-atom catalysis. We hope that this Perspective will inspire more in-depth thinking on future theoretical studies of SACs.

Boron Carbon Oxynitride as a Novel Metal-Free Photocatalyst

Boron-based nanomaterials are emerging as non-toxic, earth-abundant (photo)electrocatalyst materials in solar energy conversion for the production of solar hydrogen fuel and environmental remediation. Boron carbon oxynitride (BCNO) is a quaternary semiconductor with electronic, optical, and physicochemical properties that can be tuned by varying the composition of boron, nitrogen, carbon, and oxygen. However, the relationship between BCNO's structure and -photocatalytic activity relationship has yet to be explored. We performed an in-depth spectroscopic analysis to elucidate the effect of using two different nitrogen precursors and the effect of annealing temperatures in the preparation of BCNO. BCNO nanodisks (D = 6.7 ± 1.1 nm) with turbostratic boron nitride diffraction patterns were prepared using guanidine hydrochloride as the nitrogen source precursor upon thermal annealing at 800°C. The X-ray photoelectron spectroscopy (XPS) surface elemental analysis of the BCNO nanodisks revealed the B, C, N, and O compositions to be 40.6%, 7.95%, 37.7%, and 13.8%, respectively. According to the solid-state 11B NMR analyses, the guanidine hydrochloride-derived BCNO nanodisks showed the formation of various tricoordinate BNx(OH)3-x species, which also served as one of the photocatalytic active sites. The XRD and in-depth spectroscopic analyses corroborated the preparation of BCNO-doped hexagonal boron nitride nanodisks. In contrast, the BCNO annealed at 600 °C using melamine as the nitrogen precursor consisted of layered nanosheets composed of B, C, N, and O atoms covalently bonded in a honeycomb lattice as evidence by the XRD, XPS, and solid-state NMR analysis (11B and 13C) analyses. The XPS surface elemental composition of the melamine-derived BCNO layered structures consisted of a high carbon composition (75.1%) with a relatively low boron (5.24%) and nitrogen (7.27%) composition, which indicated the formation of BCNO-doped graphene oxides layered sheet structures. This series of melamine-derived BCNO-doped graphene oxide layered structures were found to exhibit the highest photocatalytic activity, exceeding the photocatalytic activity of graphitic carbon nitride. In this layered structure, the formation of the tetracoordinate BNx(OH)3-x(CO) species and the rich graphitic domains were proposed to play an important role in the photocatalytic activity of the BCNO-doped graphene oxides layered structures. The optical band gap energies were measured to be 5.7 eV and 4.2 eV for BCNO-doped hexagonal boron nitride nanodisks and BCNO-doped graphene oxides layered structures, respectively. Finally, BCNO exhibited an ultralong photoluminescence with an average decay lifetime of 1.58, 2.10, 5.18, and 8.14 µs for BGH01, BGH03, BMH01, BMH03, respectively. This study provides a novel metal-free photocatalytic system and provides the first structural analysis regarding the origin of BCNO-based photocatalyst.

Highly Efficient Oxidative Cyanation of Aldehydes to Nitriles over Se,S,N-tri-Doped Hierarchically Porous Carbon Nanosheets

Oxidative cyanation of aldehydes provides a promising strategy for the cyanide-free synthesis of organic nitriles. Design of robust and cost-effective catalysts is the key for this route. Herein, we designed a series of Se,S,N-tri-doped carbon nanosheets with a hierarchical porous structure (denoted as Se,S,N-CNs-x, x represents the pyrolysis temperature). It was found that the obtained Se,S,N-CNs-1000 was very selective and efficient for oxidative cyanation of various aldehydes including those containing other oxidizable groups into the corresponding nitriles using ammonia as the nitrogen resource below 100 °C. Detailed investigations revealed that the excellent performance of Se,S,N-CNs-1000 originated mainly from the graphitic-N species with lower electron density and synergistic effect between the Se, S, N, and C in the catalyst. Besides, the hierarchically porous structure could also promote the reaction. Notably, the unique feature of this metal-free catalyst is that it tolerated other oxidizable groups, and showed no activity on further reaction of the products, thereby resulting in high selectivity. As far as we know, this is the first work for the synthesis of nitriles via oxidative cyanation of aldehydes over heterogeneous metal-free catalysts.

Copper-Catalyzed Three-Component Carboboronation of Allenes Using Highly Strained Cyclic Ketimines as Electrophiles

A diastereoselective copper and NHC-ligand-catalyzed three-component difunctionalization of allenes with bis(pinacolato)diboron and 2H-azirines to afford borylated allylaziridines is described. The reaction exhibits complete diastereoselectivity and good yields, and the further chlorination of the corresponding borylated products was also performed. It is believed that the high ring-strain force of 2H-azirines facilitates the reaction. More chemical transformations of borylated allylaziridines are also reported.

Conformal Macroporous Inverse Opal Oxynitride-Based Photoanode for Robust Photoelectrochemical Water Splitting

Direct photoelectrochemical (PEC) water splitting is of prime importance in sustainable energy conversion systems; however, it is a big challenge to simultaneously control light harvesting and charge transport for the improvement of PEC performance. Herein, we report a three-dimensional ordered macroporous (3DOM) CsTaWO_6-xN_x inverse opal array as a promising candidate for the first time. To address the critical challenge, an ultrathin carbon-nitride-based layer-intercalated 3DOM CsTaWO_6-xN_x architecture as a conformal heterojunction photoanode was assembled. This state-of-the-art conformal heterojunction photoanode with carrier-separation efficiency up to 88% achieves a high current density of 4.59 mA cm^-2 at 1.6 V versus a reversible hydrogen electrode (vs RHE) under simulated AM 1.5G illumination, which is approximately 3.4 and 17 times larger than that of pristine CsTaWO_6-xN_x inverse opals and powers photoelectrodes in alkaline media, corresponding to an incident photon-to-current efficiency of 32% at 400 nm and outstanding stability for PEC water splitting. Density functional theory calculations propose that the intimate interface of a conformal photoanode optimizes the charge separation and transfer, thus enhancing the intrinsic water oxidation performance. This work enables us to elucidate the pivotal importance of 3DOM architectures and conformal heterostructures and the promising contributions to excellent PEC water-splitting applications.

Ceramic boron carbonitrides for unlocking organic halides with visible light

Photochemistry provides a sustainable pathway for organic transformations by inducing radical intermediates from substrates through electron transfer process. However, progress is limited by heterogeneous photocatalysts that are required to be efficient, stable, and inexpensive for long-term operation with easy recyclability and product separation. Here, we report that boron carbonitride (BCN) ceramics are such a system and can reduce organic halides, including (het)aryl and alkyl halides, with visible light irradiation. Cross-coupling of halides to afford new C-H, C-C, and C-S bonds can proceed at ambient reaction conditions. Hydrogen, (het)aryl, and sulfonyl groups were introduced into the arenes and heteroarenes at the designed positions by means of mesolytic C-X (carbon-halogen) bond cleavage in the absence of any metal-based catalysts or ligands. BCN can be used not only for half reactions, like reduction reactions with a sacrificial agent, but also redox reactions through oxidative and reductive interfacial electron transfer. The BCN photocatalyst shows tolerance to different substituents and conserved activity after five recycles. The apparent metal-free system opens new opportunities for a wide range of organic catalysts using light energy and sustainable materials, which are metal-free, inexpensive and stable.

Asymmetric Acceptor-Donor-Acceptor Polymers with Fast Charge Carrier Transfer for Solar Hydrogen Production

Construction of local donor-acceptor architecture is one of the valid means for facilitating the intramolecular charge transfer in organic semiconductors. To further accelerate the interface charge transfer, a ternary acceptor-donor-acceptor (A₁ -D-A₂ ) molecular junction is established via gradient nitrogen substituting into the polymer skeleton. Accordingly, the exciton splitting and interface charge transfer could be promptly liberated because of the strong attracting ability of the two different electron acceptors. Both DFT calculations and photoluminescence spectra elucidate the swift charge transfer at the donor-acceptor interface. Consequently, the optimum polymer, N₃ -CP, undergoes a remarkable photocatalytic property in terms of hydrogen production with AQY_405 nm =26.6 % by the rational design of asymmetric molecular junctions on organic semiconductors.

An efficient broad spectrum-driven carbon and oxygen co-doped g-C3N4 for the photodegradation of endocrine disrupting: Mechanism, degradation pathway, DFT calculation and toluene selective oxidation

In this study, a new type of carbon and oxygen co-doped g-C₃N₄ (PACN) was successfully synthesized by a one-step thermal polymerization method for the photodegradation of Bisphenol A (BPA) and selective oxidation of toluene to benzaldehyde. The degradation rate of BPA was 23.58 times higher than that of pristine g-C₃N₄ and the efficiency benzaldehyde formation rate without the need of any solvent increased to 5.43 times that of g-C₃N₄. At the same time, the band structure calculation of its simulated structure is performed by DFT, which shows that the introduction of oxygen linking band can adjust its band structure and obtain a smaller band gap. In addition, the PACN displays an enhanced photocatalytic degradation of BPA under the long wavelength (λ ≥ 550 nm) and NIR light irradiation (λ ≥ 760 nm), which indicates that the synthesized materials have a broad spectrum of photocatalytic activity. According to the results of secondary ion mass spectrometry (SIMS) and nuclear magnetic resonance spectroscopy (NMR), C atoms and O atoms were introduced into the original g-C₃N₄ skeleton. In addition, the intermediate products were detected by mass spectrometry (HPLC-MS), and the BPA degradation pathway was proposed. A feasible photocatalytic reaction mechanism was also proposed.

Transesterification of rapeseed oil and waste corn oil toward the production of biodiesel over a basic high surface area magnetic nanocatalyst: application of the response surface methodology in process optimization

A new, green, and recoverable catalyst is prepared for the synthesis of biodiesel.

In situ growth of metal-free snowflake-like 1D/2D phosphorus element heterostructures for photocatalytic overall pure-water splitting

In this work, we report a novel phosphorus element heterostructure with a snowflake-like morphology consisting of 1D rod-like black phosphorus (BP) and 2D flake-like red phosphorus (RP).

Highly efficient photothermal heating via distorted edge-defects in boron quantum dots

Quantum dots (QDs) are increasingly being utilized as near infrared (NIR) active photothermal agents for cancer diagnosis and therapy, with the main emphasis of current research being the enhancement of photothermal conversion efficiencies. Herein, we report the facile synthesis of 2-3 nm boron quantum dots (B QDs), which demonstrated a remarkable photothermal conversion efficiency of 57% under NIR excitation. This outstanding performance can be attributed to the alteration of the electronic structure, which was a result from the distorted edge-effect induced by the unique empty orbit of B atoms in the B QDs. These results can be verified by B K-edge near edge X-ray absorption fine structure (NEXAFS), high-resolution transmission electron microscopy (HR-TEM) and density functional theory (DFT) calculations. The results demonstrate that B QDs represent a promising new and non-toxic agent for both multimodal NIR-driven cancer imaging and photothermal therapy. This work thus identifies B QDs as an exciting new and theranostic agent for cancer therapy. Furthermore, the synthetic strategy used here to synthesize the B QDs was simple and easily scalable.

Desulfurization on Boron Nitride and Boron Nitride-based Materials

Combustion of liquid fuels containing sulfur compounds is highly unfavorable due to the adverse effects caused by the resultant SO_x emission. Consequently, catalytic and adsorptive materials having the capacity to eliminate the sulfur compounds from liquid fuels are very attractive. Hexagonal boron nitride (BN), with its interesting chemical and physical properties, finds applications in diverse fields, especially in energy and environmental applications. Recently, BN and BN-based materials have gained significant interest in emerging desulfurization processes such as oxidative desulfurization and adsorptive desulfurization. In this review, BN and BN-based materials are elaborately discussed in the context of their use in various desulfurization techniques. A brief description about the different desulfurization processes is provided at the outset. The relationship between the characteristics (the defects, morphology, porosity and surface area) of BN and desulfurization efficiency is also summarized. Furthermore, the mechanistic insights regarding the action of BN materials in the desulfurization processes are discussed. With this review, the synthetic strategies for designing the novel BN-based catalysts/adsorbents for the effective desulfurization of liquid fuels can be grasped.

Facile synthesis of a BCN nanofiber and its ultrafast adsorption performance

Boron carbonitride (BCN) nanofibers with rapid and efficient adsorption performance were prepared by electrospinning technology. TEM, XRD, XPS and N₂ adsorption–desorption isotherms were performed to study the microstructure of the nanofibers. The results showed that the BCN fibers synthesized at 1000 °C (BCN-1000) have good crystallinity and high specific surface areas (403 m² g⁻¹). BCN-1000 nanofibers adsorb 70% of amino black 10B (AB-10B) within 10 minutes and reach adsorption equilibrium within 60 minutes. Compared with previous reports, it is found that the adsorption rate of BCN-1000 nanofibers to amino black (AB-10B) is much higher than that of other adsorbents. And BCN nanofibers exhibit a large adsorption capacity (625 mg g⁻¹). In addition, the process of AB-10B adsorption on BCN nanofibers was systematically investigated, which was in accordance with the pseudo-second-order kinetics model and Langmuir isotherm model.

Boron carbonitride (BCN) nanofibers with rapid and efficient adsorption performance were prepared by electrospinning technology.

Simultaneous Recovery of Display Panel Waste Glass and Wastewater Boron by Chemical Oxo-precipitation with Fluidized-Bed Heterogeneous Crystallization

Silica-based carrier is a promising material for recovery of metal and nonmetal contaminants in chemical oxo-precipitation-fluidized bed crystallization (COP-FBC) system. Boron species are an essential element for plant growth and can cause health concerns in human beings at high concentrations in water environments. The composition of thin-film transistor liquid crystal display (TFT-LCD) contains a wide variety of metal oxides and can be tailored as promising functional mesoporous carriers for boron crystallization recovery in the presence of barium ions and hydrogen peroxide. In this study, waste-derived mesoporous aluminosilicate (MAS) nanomaterial in the presence of barium ions and hydrogen peroxide was used as a carrier for sustainable recovery of crystallized boron, a priority wastewaters pollutant. The MAS shows the hierarchically homogeneous distribution of nanostructured aluminosilicate particles with an average size of 12.8 ± 3.6 nm on the surface after the activation with Na₂CO₃ at 1000 °C. Moreover, the negatively charged surface and the mesoporous structure of MAS enhance the adsorption of Ba²⁺ onto MAS, and the Langmuir adsorption capacity of 105 mg/g is achieved, which is conducive to the enhancement of the recovery of boron species. Moreover, the recovery efficiency and crystallization ratio of boron by MAS can be up to 84.5 and 93.4%, respectively. The cross-sectional scanning electron microscopy images and the high-temperature X-ray diffraction results confirm the boron recovery mechanism that the negatively charged functional group as well as the mesoporosity of MAS triggers the rapid formation of needle-shaped precipitates of barium peroxoborate, and then converted to barium borate after calcination at 1050 °C. Results obtained in this study clearly demonstrate the possibility of fabricating environmentally benign mesoporous aluminosilicate adsorbents from TFT-LCD waste to sustainably recover and crystallize boron species from water and wastewater in COP-FBC.

Modulation of Polymeric Carbon Nitrides through Supramolecular Preorganization for Efficient Photocatalytic Hydrogen Generation

Supramolecular pre-assembly by design is an effective strategy to adapt the physicochemical properties of polymeric carbon nitrides (PCNs) to improve their solar conversion performance. A new supramolecular preorganization protocol, which employs H₂ O as the self-assembly medium and sodium persulfate as a modifier, is proposed to modulate the textural and photoelectronic features of PCNs for efficient visible-light H₂ evolution. Sodium persulfate is revealed to precisely tailor the final carbon nitride polymers with unusual porous layered structures and promoted charge separation and migration kinetics. As a result, the modulated PCNs with optimized structures show a greatly enriched activity for photocatalytic H₂ generation compared to the analogous materials derived from melamine without the modifier.

Phosphorylation of Polymeric Carbon Nitride Photoanodes with Increased Surface Valence Electrons for Solar Water Splitting

Overcoming the sluggish kinetics of the water oxidation is the key to a high performance for solar water splitting. Herein, phosphorylated polymeric carbon nitride (PCN) photoanodes were developed and showed enhanced photocurrent densities for solar water splitting. A photocatalytic efficiency of 120 μA cm^-2 was achieved in the basic solution (1.0 m NaOH) without sacrificial agents. In this system, phosphates were ionically anchored on the surface of PCN, and the modified films showed significantly increased density of valence electrons, and thus promoting photocatalytic efficiency.

Propane oxidative dehydrogenation over highly selective hexagonal boron nitride catalysts: The role of oxidative coupling of methyl

Hexagonal boron nitride (h-BN) catalyst has recently been reported to be highly selective in oxidative dehydrogenation of propane (ODHP) for olefin production. In addition to propene, ethylene also forms with much higher overall selectivities to C2-products than to C1-products. In this work, we report that the reaction pathways over the h-BN catalyst are different from the V-based catalysts in ODHP. Oxidative coupling reaction of methyl, an intermediate from the cleavage of C─C bond of propane, contributes to the high selectivities to C2-products, leading to more C2-products than C1-products over the h-BN catalyst. This work not only provides insight into the reaction mechanisms involved in ODHP over the boron-based catalysts but also sheds light on the selective oxidation of alkanes such as direct upgrading of methane via oxidative upgrading to ethylene or CH _x O _y on boron-based catalysts.

Effects of ball-milling treatment on physicochemical properties and solid base activity of hexagonal boron nitrides

Hexagonal boron nitride solid base catalysts were prepared by simple ball-milling at various rotation speeds of a commercial low-surface area boron nitride.

Palladium immobilized on functionalized hypercrosslinked polymers: a highly active and recyclable catalyst for Suzuki–Miyaura coupling reactions in water

Three palladium complexes were synthesized via an external cross-linking reaction and found to be effective heterogeneous catalysts for the Suzuki–Miyaura reaction.

In Situ-Fabricated 2D/2D Heterojunctions of Ultrathin SiC/Reduced Graphene Oxide Nanosheets for Efficient CO2 Photoreduction with High CH4 Selectivity

Photoreduction of CO₂ into fuel molecules such as CH₄ represents a promising route to simultaneously explore renewable energy and alleviate global warming. However, the implementation of such a process is hampered by low product yields and poor selectivity. A 2D/2D heterojunction of ultrathin SiC and reduced graphene oxide (RGO) nanosheets was fabricated in situ for efficient and selective photoreduction of CO₂ . Ultrathin SiC suppresses significant charge recombination in the bulk phase, thus providing more energetic electrons. The robust 2D/2D heterojunction allows fast transfer of energetic electrons from SiC to RGO. Combining the vital role of RGO in facilitating CO₂ activation, the optimized SiC/RGO exhibits an electron-transfer rate of 58.17 μmol h^-1  g^-1 towards CO₂ reduction, 2.7 times that of pure SiC (20.25 μmol h^-1  g^-1 ). About 92 % of the transferred electrons from SiC are devoted to generating CH₄ (6.72 μmol h^-1  g^-1 ). Such high efficiency and selectivity are mainly a result of the densely accumulated energetic electrons within RGO, which facilitate the eight-electron process to produce CH₄ . This work will inspire the design of catalyst/cocatalyst systems for efficient and selective photoreduction of CO₂ .