Boron Nitride Catalysts Research Articles

An efficient multi-path to active peroxymonosulfate by carbon and sulfur co-doped boron nitride for antibiotics degradation: An emerging electron-transfer pathway at activated-S sites

Metal-free catalysis is considered promising for the green degradation of aqueous organic pollutants. Herein, a novel non-metallic heteroatom-doped boron nitride (h-BN) catalyst with carbon and sulfur doping, named SC-BN, was successfully prepared. Under optimal conditions, the SC-BN/peroxymonosulfate (PMS) system can achieve an impressive 99.4 % levofloxacin removal within 90 min (kobs = 0.0531 min−1). In-depth physicochemical characterizations have identified B-N-C and C-S-C as co-active functional groups. The electrochemical characterization and density functional theory (DFT) calculations further verified the enhanced electron transfer pathway (ETP) at S sites, which was activated by an emerging electric field. h-BN as a highly electroactive material also plays a positive role in regulation. Besides, the electrical energy per order (EE/O = 6.65 kWh/m3) and toxicity evaluation results exhibited the practical potential for eco-friendly detoxification and degradation of various refractory contaminants. In summary, this study puts forth a novel metal-free PMS activation process with an efficient multi-path mechanism and provides a theoretical foundation for future research.

Oxygen-Activated Boron Nitride for Selective Photocatalytic Coupling of Methanol to Ethylene Glycol.

The controllable photocatalytic C-C coupling of methanol to produce ethylene glycol (EG) is a highly desirable but challenging objective for replacing the current energy-intensive thermocatalytic process. Here, we develop a metal-free porous boron nitride catalyst that demonstrates exceptional selectivity in the photocatalytic production of EG from methanol under mild conditions. Comprehensive experiments and calculations are conducted to thoroughly investigate the reaction mechanism, revealing that the OB3 unit in the porous BN plays a critical role in the preferential activation of C-H bond in methanol to form ⋅CH2OH via a concerted proton-electron transfer mechanism. More prominent energy barriers are observed for the further dehydrogenation of the ⋅CH2OH intermediate on the OB3 unit, inhibiting the formation of some other by-products during the catalytic process. Additionally, a small downhill energy barrier for the coupling of ⋅CH2OH in the OB3 unit promotes the selective generation of EG. This study provides valuable insights into the underlying mechanisms and can serve as a guide for the design and optimization of photocatalysts for efficient and selective EG production under mild conditions.

Oxygen‐Activated Boron Nitride for Selective Photocatalytic Coupling of Methanol to Ethylene Glycol

AbstractThe controllable photocatalytic C−C coupling of methanol to produce ethylene glycol (EG) is a highly desirable but challenging objective for replacing the current energy‐intensive thermocatalytic process. Here, we develop a metal‐free porous boron nitride catalyst that demonstrates exceptional selectivity in the photocatalytic production of EG from methanol under mild conditions. Comprehensive experiments and calculations are conducted to thoroughly investigate the reaction mechanism, revealing that the OB3 unit in the porous BN plays a critical role in the preferential activation of C−H bond in methanol to form ⋅CH2OH via a concerted proton‐electron transfer mechanism. More prominent energy barriers are observed for the further dehydrogenation of the ⋅CH2OH intermediate on the OB3 unit, inhibiting the formation of some other by‐products during the catalytic process. Additionally, a small downhill energy barrier for the coupling of ⋅CH2OH in the OB3 unit promotes the selective generation of EG. This study provides valuable insights into the underlying mechanisms and can serve as a guide for the design and optimization of photocatalysts for efficient and selective EG production under mild conditions.

Enhanced PMS activation by Mn2O3-loaded h-BN for levofloxacin removal: Unveiling the dominant influence of non-free radical pathway and N-Mn-mediated promotion of stable, long-lived Mn(IV) species

The Mn2O3-loaded hexagonal boron nitride (h-BN-Mn) catalyst for peroxymonosulfate (PMS) activation was successfully synthesized using a one-step calcination process. The h-BN-Mn/PMS system achieved an impressive 97 % levofloxacin removal within a mere 90-minute timeframe. This catalyst, h-BN-Mn, effectively addresses the challenge of elevated manganese leaching rates and exhibits a broad pH degradation spectrum spanning from 3 to 11. Notably, it maintained robust degradation performance over five cycles, showcasing the potential for large-capacity water treatment when integrated with a polyvinylidene fluoride (PVDF) membrane (h-BN-Mn@PVDF), resulting in an 83.8 % removal rate over 6 h. In-depth analysis revealed three distinct degradation pathways. Primarily, the generation of reactive oxygen species (ROS), including singlet oxygen (1O2), played a pivotal role. This was complemented by direct electron transfer from the contaminant to the catalyst-PMS complex, augmented by contributions from Mn(IV) species derived from the complex. This study not only presents a compelling instance of antibiotic degradation through multi-pathway activated PMS but also sheds light on the remarkable synergistic effects achieved by combining manganese oxide with boron and nitrogen compounds.

Adsorption and activation of small molecules on boron nitride catalysts.

Hexagonal boron nitride possesses a unique layered structure, high specific surface area and similar electronic properties as graphene, which makes it not only a promising catalyst support, but also a highly effective metal-free catalyst in the booming field of green chemistry. Reactions involving small molecules (e.g., oxygen, low carbon alkanes, nitrogen and carbon dioxide) have always been a hot topic in catalytic research, especially associated with the adsorption and activation regime of different forms of small molecules on catalysts. In this review, we have investigated the adsorption of different small molecules and the relevant activation mechanisms of four typical chemical bonds (OO, C-H, NN, CO) on hexagonal boron nitride. Recent progress on approaches adopted to enhance the activation capacity such as doping, defect engineering and heterostructuring are summarized, highlighting the potential applications of nonmetallic hexagonal boron nitride catalysts in various reactions. This comprehensive investigation offers a reference point for the enhanced mechanistic understanding and future design of effective and sustainable catalytic systems based on boron nitride.

Highly Porous Boron Nitride as a Metal-Free Heterogeneous Catalyst for Cycloaddition of CO2 to Epoxides

Boron nitride has received much attention as an emerging heterogeneous catalyst. Porous boron nitride catalysts were synthesized using boric acid (B) and urea (U) at various molar ratio via pyrolysis...

Insights into reaction pathway induced by d orbital occupancy on cobalt supported boron nitride for N2O catalytic decomposition

Nitrous oxide (N2O), as a typical greenhouse gas, is urgent to be eliminated to address the global climate issue. Developing low-temperature N2O decomposition catalysts is crucial for mitigating greenhouse gas emissions. Herein, we propose a Cobalt-supported boron nitride (Co-BN) catalyst with a low reaction energy barrier (1.37 eV) using density functional theory calculations. The coordination environment is critical to the reaction mechanism and energy barrier, where the CoN3 configuration (Co coordinated with three N atoms) triggers the Eley-Rideal (E-R) mechanism, but the CoB3 configuration (Co coordinated with three B atoms) engenders the Langmuir-Hinshelwood (L-H) mechanism. Fundamentally, the reaction mechanism is dominated by d orbital occupancy. Following the adsorption of *O intermediate, a fully filled d orbital is realized on *O-CoN3, which prevents N2O from bonding with Co, thus following the E-R mechanism through directly interacting with *O specie. Conversely, the partially unoccupied d orbital is identified on *O-CoB3, provinding the bonding site on Co for N2O molecule, thereby leading to the L-H mechanism. Our work provides a novel N2O decomposition catalyst theoretically, and the insights into the relationship between d orbital occupancy and the reaction mechanism, would pave a new avenue for the design of N2O decomposition catalysts.

Efficient and Selective Hydrogenolysis of 5‐Hydroxymethylfurfural to 2,5‐Dimethylfuran by a Bimetallic Copper‐Palladium Catalyst on a Carbon‐Doped Boron Nitride Support

AbstractIn the present world, 2,5‐dimethylfuran (DMF), as a renewable liquid fuel, is valuable for maintaining ecological stability. Therefore, it is quite necessary to enhance the selectivity of DMF during the hydrodeoxygenation (HDO) of 5‐hydroxymethylfurfural (HMF) to DMF. In this paper, a copper‐palladium bimetal supported on carbon‐doped boron nitride (BCN) catalyst was prepared as a class of catalyst for HDO. Notably, under the combined action of Cu−Pd alloy and support, the catalyst of 10Cu3Pd/BCN showed remarkable activity with high selectivity (99.2 %) for DMF. In addition, the packing and dispersion of the alloy particles by the carrier improved the cycling performance of the catalyst. Therefore, the selection of 10Cu3Pd/BCN as a catalyst for HDO has excellent application prospects.

Mechanistic Insights into Radical-Induced Selective Oxidation of Methane over Nonmetallic Boron Nitride Catalysts

Boron-based nonmetallic materials (such as B2O3 and BN) emerge as promising catalysts for selective oxidation of light alkanes by O2 to form value-added products, resulting from their unique advantage in suppressing CO2 formation. However, the site requirements and reaction mechanism of these boron-based catalysts are still in vigorous debate, especially for methane (the most stable and abundant alkane). Here, we show that hexagonal BN (h-BN) exhibits high selectivities to formaldehyde and CO in catalyzing aerobic oxidation of methane, similar to Al2O3-supported B2O3 catalysts, while h-BN requires an extra induction period to reach a steady state. According to various structural characterizations, we find that active boron oxide species are gradually formed in situ on the surface of h-BN, which accounts for the observed induction period. Unexpectedly, kinetic studies on the effects of void space, catalyst loading, and methane conversion all indicate that h-BN merely acts as a radical generator to induce gas-phase radical reactions of methane oxidation, in contrast to the predominant surface reactions on B2O3/Al2O3 catalysts. Consequently, a revised kinetic model is developed to accurately describe the gas-phase radical feature of methane oxidation over h-BN. With the aid of in situ synchrotron vacuum ultraviolet photoionization mass spectroscopy, the methyl radical (CH3•) is further verified as the primary reactive species that triggers the gas-phase methane oxidation network. Theoretical calculations elucidate that the moderate H-abstraction ability of predominant CH3• and CH3OO• radicals renders an easier control of the methane oxidation selectivity compared to other oxygen-containing radicals generally proposed for such processes, bringing deeper understanding of the excellent anti-overoxidation ability of boron-based catalysts.

Unraveling Radical and Oxygenate Routes in the Oxidative Dehydrogenation of Propane over Boron Nitride.

Oxidative dehydrogenation of propane (ODHP) is an emerging technology to meet the global propylene demand with boron nitride (BN) catalysts likely to play a pivotal role. It is widely accepted that gas-phase chemistry plays a fundamental role in the BN-catalyzed ODHP. However, the mechanism remains elusive because short-lived intermediates are difficult to capture. We detect short-lived free radicals (CH3•, C3H5•) and reactive oxygenates, C2-4 ketenes and C2-3 enols, in ODHP over BN by operando synchrotron photoelectron photoion coincidence spectroscopy. In addition to a surface-catalyzed channel, we identify a gas-phase H-acceptor radical- and H-donor oxygenate-driven route, leading to olefin production. In this route, partially oxidized enols propagate into the gas phase, followed by dehydrogenation (and methylation) to form ketenes and finally yield olefins by decarbonylation. Quantum chemical calculations predict the >BO dangling site to be the source of free radicals in the process. More importantly, the easy desorption of oxygenates from the catalyst surface is key to prevent deep oxidation to CO2.

Auto-accelerated dehydrogenation of alkane assisted by in-situ formed olefins over boron nitride under aerobic conditions

Oxidative dehydrogenation (ODH) of alkane over boron nitride (BN) catalyst exhibits high olefin selectivity as well as a small ecological carbon footprint. Here we report an unusual phenomenon that the in-situ formed olefins under reactions are in turn actively accelerating parent alkane conversion over BN by interacting with hydroperoxyl and alkoxyl radicals and generating reactive species which promote oxidation of alkane and olefin formation, through feeding a mixture of alkane and olefin and DFT calculations. The isotope tracer studies reveal the cleavage of C-C bond in propylene when co-existing with propane, directly evidencing the deep-oxidation of olefins occur in the ODH reaction over BN. Furthermore, enhancing the activation of ethane by the in-situ formed olefins from propane is successfully realized at lower temperature by co-feeding alkane mixture strategy. This work unveils the realistic ODH reaction pathway over BN and provides an insight into efficiently producing olefins.

Exploring hexagonal boron nitride as an efficient visible light induced catalyst for the remediation of recalcitrant antibiotic from aqueous media

Hexagonal boron nitride (h-BN) is a novel non-metallic material which is newly discovered in the field of photocatalysis due to its high surface area, excellent optical features and high electrical conductivity. Herein, hexagonal boron nitride whiskers were fabricated by using the polymeric precursor method and, the photocatalytic degradation performance was measured towards tetracycline antibiotic under visible-light-illumination. The morphological, physical, and optical features of the catalyst were identified by several characterization analyses. The characteristic peaks associated with the hexagonal phase of boron nitride were determined and high crystallinity of h-BN was confirmed by X-ray diffraction analysis. The characteristic B−N absorption peaks were detected in the Fourier transfer infrared spectrum. Brunauer− Emmet−Teller specific surface area of the boron nitride catalyst was calculated as 1019 m2/g which was relatively high, supplying abundant active regions to interact with the target pol- lutant. In photocatalytic degradation experiments, 91.9% of tetracycline decomposition was achieved within 180 min with a catalyst dosage of 0.2 g/L and initial concentration of 10 mg/L. The outstanding catalytic activity of the h-BN catalyst was attributed to the high surface area and negatively charged groups on the surface which captured the photo-induced holes and inhibited the recombination rate of charge carriers. These findings highlight the potential ap- plication of h-BN in the field of photocatalytic processes.

Green synthesis of benzimidazole derivatives by using zinc boron nitride catalyst and their application from DFT (B3LYP) study

A new zinc-based boron nitride (Zn-BNT) material was synthesized from boron nitride and zinc acetate in 95% yield. The morphological and spectroscopic properties of Zn-BNT were elucidated by SEM, XRD, BET, DSC-TGA, and FT-IR. Zn-BNT catalyzed the synthesis of benzimidazoles (3a–3h) through a reaction between o-phenylenediamine and different aromatic aldehydes under microwave conditions for 15 min. The compounds were purified by silica-gel chromatography. The synthesized compounds were characterized by FT-IR, 1H-NMR, 13C-NMR, and elemental analysis. Zn-BNT was reused eight times with only a 5% loss of catalytic activity. Furthermore, 2-(4-fluorophenyl)-1H-benzo[d]imidazole (3f) was selected for a computational study of the IR and NMR spectrum, which matched the experimentally generated spectra. The HOMO-LUMO gap was 4.48, and the Fukui function analysis showed high activity in the reactive sites.

Mixing nitrogen-containing compounds for synthesis of porous boron nitride for improved porosity, surface functionality, and solid base catalytic activity

Porous boron nitride was synthesized using boric acid with urea and/or hexamethylenetetramine (HMTA) via pyrolysis method. X-ray diffraction and Fourier transform infrared measurements indicated that the synthesized boron nitride has a turbostratic structure with both amino and hydroxyl group on the surface. The synthesis using a mixture of two nitrogen-containing precursors was found to not only significantly increase the porosity, but also improve the surface functionality. X-ray photoelectron spectroscopy and B K-edge and O K-edge X-ray absorption fine structure measurements revealed that the proportion of amino and hydroxyl groups on the surface increased with increasing concentration of HMTA during synthesis. Solid-state 11B nuclear magnetic resonance spectroscopy indicated that all samples contained trigonal B-N, trigonal B-O and tetrahedral B-O sites, and that samples prepared with high concentrations of HMTA had less tetrahedral B-O sites, suppressing the formation of BOx species as byproducts. Solid base catalytic activity was evaluated through Knoevenagel condensation, and the catalytic performance was significantly improved by synthesizing boron nitride catalyst using a mixture of the two nitrogen-containing precursors. The enhancement of the activity was influenced by the development of the pore structure as well as the emergence of functional groups on the surface.

Understanding the effect of transition metals and vacancy boron nitride catalysts on activity and selectivity for CO2 reduction reaction to valuable products: A DFT-D3 study

Single-atom catalysts have recently emerged as a promising approach for catalyzing the electrochemical CO2 reduction reaction (CRR). Transition metal (TM) atom doping to 2-dimensional layer material has been studied for CRR, but compared to studies on TM doped single vacancy (TM-SV) sites, those on double vacancies (TM-DV) sites are minor. In this research, we investigated the doping of 26 (3d-, 4d-, and 5d-groups) TM atoms to the DV of boron nitride nanosheets (BN) using the dispersion-corrected density functional theory method for the complete CRR mechanism. We analyzed the limiting potential of the reactions of different TM-DVBN using the integrated crystal orbital Hamiltonian partition (ICOHP) of TM–O binding, universal descriptor, charge, and the number of valence electrons. We found the volcano plot model which suggests that a moderate OH binding energy of around −0.50 eV, the universal descriptor value around 9.40, and the ICOHP descriptor around −0.20 will provide the lowest limiting potential for CRR. From these studies, we find Ni-DVBN is the most reactive and can produce CH3OH at −0.48 V. This is much better than Ni-SVBN, which requires −1.0 V to produce HCOOH also lower than Fe-SVBN (−0.52 V), which was the best catalyst in the previous study of TM-SVBN. This shows that Ni doping to DVBN is more effective for CRR compared to doping to SVBN.

Cobalt Supported on BN Catalyst with High B‐O Defects and Its Efficient Hydrodeoxygenation Performance of HMF to DMF**

AbstractIn this paper, a non‐noble catalyst was prepared by a simple homogeneous precipitation method and could be applied for 5‐hydroxymethylfurfural (HMF) hydrodeoxygenation (HDO) to 2, 5‐dimethylfuran (DMF). The catalyst was characterized by SEM, TEM, XRD, FT‐IR, BET, XPS, ICP and H2‐TPR. The cobalt species in the catalysts dispersed on the surface of boron nitride (BN) evenly. There is a strong interaction between BN and cobalt species in the Co/BN catalysts with vast B−O defects. Under the optimal conditions, HMF can be completely converted and the selectivity of Co/BN catalyst for DMF can reach as high as 91.67 %. It is crucial that the stability of the catalyst was maintained after five cycles by simple centrifugation. Due to its simple preparation process, low cost and high selectivity, the catalyst will be applied widely in the area of industrial catalysis.

Green Synthesis of Benzimidazole Derivatives by Using Zinc Boron Nitride Catalyst and Their Application of DFT (B3LYP) Study

Green Synthesis of Benzimidazole Derivatives by Using Zinc Boron Nitride Catalyst and Their Application of DFT (B3LYP) Study

Binary molten salts mediated defect engineering on hexagonal boron nitride catalyst with long-term stability for aerobic oxidative desulfurization

Molten salts mediation is a potential strategy for the development of functional materials. Herein, a controllable defect engineering on the hexagonal boron nitride (h-BN) was approached via the binary molten salts (BMS) mediated strategy. The as-synthesized h-BN catalyst had a high crystalline structure with adequate nitrogen-terminated defects, which can work as the reactive sites for the adsorption and activation of molecular oxygen in the aerobic oxidative desulfurization of fuel. These reactive sites on the high crystalline h-BN catalyst showed outstanding stability with only a 1% loss of activity after continuous operation for 120 h. Moreover, the induced number of defects in the high-crystalline h-BN varied with the melting point of BMS, which could be simply modulated by adjusting its binary composition. Thus, via adjusting the melting temperature of BMS close to the eutectic point, a defective high-crystalline h-BN was optimized as the high-performance catalyst, achieving 96% of sulfur conversion in the aerobic oxidation of refractory aromatic sulfur compounds, and remaining active after 15 times of the recycling experiment. This work provides a new approach for the controllable synthesis of high-performance h-BN in the mediation of molten salts.

Defect Engineering on Boron Nitride for O2 Activation and Subsequent Oxidative Desulfurization.

The rational design of highly active hexagonal boron nitride (h-BN) catalysts at the atomic level is urgent for aerobic reactions. Herein, a doping impurity atom strategy is adopted to increase its catalytic activities. A series of doping systems involving O, C impurities and B, N antisites are constructed and their catalytic activities for molecular O2 have been studied by density functional theory (DFT) calculations. It is demonstrated that O2 is highly activated on ON and BN defects, and moderately activated on CB and CN defects, however, it is not stable on NB and OB defects. The subsequent application in oxidative desulfurization (ODS) reactions proves the ON and C-doped (CB , CN ) systems to be good choice for sulfocompounds oxidization, especially for dibenzothiophene (DBT). While the BN antisite is not suitable for such aerobic reaction due to the extremely stable B-O* -B species formed during the oxidation process.

High-performance and stable Ru-Pd nanosphere catalyst supported on two-dimensional boron nitride nanosheets for the hydrogenation of furfural via water-mediated protonation

Bimetallic Ru-Pd catalysts are increasingly being investigated for applications in the upgrading of bio-oils to biofuels, owing to their high catalytic activities. Similarly, the recent development of Ru-Pd alloyed nanoparticle (NP) incorporated into hexagonal boron nitride (h-BN) catalysts that can be utilized for tuning the selectivity of desired products has also received considerable attention. In the present study, nanoclusters of Ru0-Pd0 that self-assemble into spherical-like Ru-Pd bimetallic catalytic sites were successfully grown on the surfaces of BN nanosheets (Ru-Pd/BN NCs) via microwave irradiation for 30 s. HR-TEM investigations revealed the formation of 25 nm sized Ru-Pd nanoparticles comprising ≤ 2 nm hexagonal closed-pack (hcp) Ru-Pd clusters with Ru crystallites on the BN nanosheets. Further, furfural was effectively converted into furfural alcohol at a lower temperature (150 °C) and valuable cyclopentanone was obtained at a higher temperature (>250 °C) over the Ru-Pd/BN catalyst through the protonation of water molecules. Furthermore, various solvents namely 2-propanol, toluene, and cyclohexane were also used to achieve the production of furan and tetrahydrofuran over the Ru-Pd/BN catalyst via the decarbonylation of furfural under mild reaction conditions. Moreover, for real-time upgrading, furfural-rich bio-oil produced by the pyrolysis of date-tree biomass was processed over the Ru-Pd/BN catalyst to obtain a maximum of 97% furfural conversion with a 71% FFA yield at 150 °C. The stability and reusability of the catalyst were also determined. The results demonstrated that the Ru-Pd/BN catalyst is highly active and chemically stable, and is therefore suitable for industrial applications.