Abstract:Hexagonal boron nitride (h‐BN) is regarded as a graphene analogue and exhibits important characteristics and vast application potentials. However, discovering a facile method for the preparation of nanoporous crystalline h‐BN nanosheets (h‐BNNS) is still a challenge. Herein, a novel and simple route for the conversion of amorphous h‐BN precursors into highly crystalline h‐BNNS was achieved through a successive dissolution–precipitation/crystallization process in the presence of magnesium. The h‐BNNS has high c… Show more
“…840 o C), 28 high bandgap (5-6 eV), 8,25,[29][30] catalytic activity, [31][32][33][34][35] and low cost. Recently, h-BN/h-BNNS 31,[34][35][36] and h-BN hybrids [37][38][39] have been shown to be promising metal-free catalysts for a variety of reactions. Notably, h-BN was recently shown to be an excellent catalyst for the selective oxidative dehydrogenation (ODH) of propane to propene, a critical feedstock chemical.…”
Hexagonal boron nitride nanosheets (h-BNNS), the isoelectronic analog to graphene, have received interest over the past decade due to their high thermal oxidative resistance, high bandgap, catalytic activity, and low cost. The functional groups that terminate boron and nitrogen zigzag and/or armchair edges directly affect their chemical, physical, and electronic properties. However, an understanding of the molecular edge termination present in h-BNNS is lacking. Here, high-resolution magic-angle spinning (MAS) solid-state NMR (SSNMR) spectroscopy, and plane-wave density-functional theory (DFT) calculations are used to determine the molecular edge termination in exfoliated h-BNNS. 1H → 11B crosspolarization MAS (CPMAS) SSNMR spectra of h-BNNS revealed multiple hydroxyl/oxygen coordinated boron edge sites that were not detectable in direct excitation experiments. A dynamic nuclear polarization (DNP)-enhanced 1H → 15N CPMAS spectrum of h-BNNS displayed four distinct 15N resonances while a 2D 1H{14N} dipolar-HMQC spectrum acquired with fast MAS revealed three distinct 14N environments. Plane-wave DFT calculations were used to construct model edge structures and predict the corresponding 11B, 14N and 15N SSNMR spectra. Comparison of the experimental and predicted SSNMR spectra confirms that zigzag and armchair edges with both amine and boron hydroxide/oxide termination are present. The detailed characterization of h-BNNS molecular edge termination will prove useful for many material science applications. The techniques outlined here should also be applicable to understand the molecular edge terminations in other 2D materials.
“…840 o C), 28 high bandgap (5-6 eV), 8,25,[29][30] catalytic activity, [31][32][33][34][35] and low cost. Recently, h-BN/h-BNNS 31,[34][35][36] and h-BN hybrids [37][38][39] have been shown to be promising metal-free catalysts for a variety of reactions. Notably, h-BN was recently shown to be an excellent catalyst for the selective oxidative dehydrogenation (ODH) of propane to propene, a critical feedstock chemical.…”
Hexagonal boron nitride nanosheets (h-BNNS), the isoelectronic analog to graphene, have received interest over the past decade due to their high thermal oxidative resistance, high bandgap, catalytic activity, and low cost. The functional groups that terminate boron and nitrogen zigzag and/or armchair edges directly affect their chemical, physical, and electronic properties. However, an understanding of the molecular edge termination present in h-BNNS is lacking. Here, high-resolution magic-angle spinning (MAS) solid-state NMR (SSNMR) spectroscopy, and plane-wave density-functional theory (DFT) calculations are used to determine the molecular edge termination in exfoliated h-BNNS. 1H → 11B crosspolarization MAS (CPMAS) SSNMR spectra of h-BNNS revealed multiple hydroxyl/oxygen coordinated boron edge sites that were not detectable in direct excitation experiments. A dynamic nuclear polarization (DNP)-enhanced 1H → 15N CPMAS spectrum of h-BNNS displayed four distinct 15N resonances while a 2D 1H{14N} dipolar-HMQC spectrum acquired with fast MAS revealed three distinct 14N environments. Plane-wave DFT calculations were used to construct model edge structures and predict the corresponding 11B, 14N and 15N SSNMR spectra. Comparison of the experimental and predicted SSNMR spectra confirms that zigzag and armchair edges with both amine and boron hydroxide/oxide termination are present. The detailed characterization of h-BNNS molecular edge termination will prove useful for many material science applications. The techniques outlined here should also be applicable to understand the molecular edge terminations in other 2D materials.
“…7 ) 28 . The yield of quinoline for F-ND catalysts is also higher than ND catalysts, illustrating that F-ND catalysts have better dehydrogenation activity, indicating a broad application in dehydrogenation reaction fields 29 . Fig.…”
Styrene is one of the most important industrial monomers and is traditionally synthesized via the dehydrogenation of ethylbenzene. Here, we report a photo-induced fluorination technique to generate an oxidative dehydrogenation catalyst through the controlled grafting of fluorine atoms on nanodiamonds. The obtained catalyst has a fabulous performance with ethylbenzene conversion reaching 70% as well as styrene yields of 63% and selectivity over 90% on a stream of 400 °C, which outperforms other equivalent benchmarks as well as the industrial K−Fe catalysts (with a styrene yield of 50% even at a much higher temperature of ca. 600 °C). Moreover, the yield of styrene remains above 50% after a 500 h test. Experimental characterizations and density functional theory calculations reveal that the fluorine functionalization not only promotes the conversion of sp3 to sp2 carbon to generate graphitic layers but also stimulates and increases the active sites (ketonic C=O). This photo-induced surface fluorination strategy facilitates innovative breakthroughs on the carbocatalysis for the oxidative dehydrogenation of other arenes.
“…The h-BN nanosheets were highly crystalline with an interlayer distance of 3.6 Å, which was in accordance with the previous reports. 47 , 49 In addition, the interlayer distance of Au NPs was 2.2 Å ( Figure 4 C). The elemental mapping analysis of the obtained h-BN/Au/SiO 2 -850, including Au center, B and N from h-BN layer, and Si and O from the silica support, exhibited that both the original silica support and the post-encapsulated h-BN layer were uniformly distributed at the position of Au NPs ( Figure 4 D–I).…”
Section: Resultsmentioning
confidence: 95%
“… 43 (2) When used as a support, h-BN possesses the ability to modulate the interfacial electronic effect on metal NPs, leading to enhanced catalytic activity. 44 − 47 (3) h-BN exhibits nanoporous architecture with high surface areas. 48 , 49 However, as a nonredox active support, h-BN-derived SMSI materials cannot be fabricated through the traditional impregnation/high-temperature treatment pathway.…”
Strong
metal–support interaction (SMSI) is recognized as
a pivotal strategy in hetereogeneous catalysis to prevent the sintering
of metal nanoparticles (NPs), but issues including restriction of
supports to reducible metal oxides, nonporous architecture, sintering
by thermal treatment at >800 °C, and unstable nature limit
their
practical application. Herein, the construction of non-oxide-derived
SMSI nanocatalysts based on highly crystalline and nanoporous hexagonal
boron nitride (h-BN) 2D materials was demonstrated via in situ encapsulation
and reduction using NaBH
4
, NaNH
2
, and noble
metal salts as precursors. The as-prepared nanocatalysts exhibited
robust thermal stability and sintering resistance to withstand thermal
treatment at up to 950 °C, rendering them with high catalytic
efficiency and durability in CO oxidation even in the presence of
H
2
O and hydrocarbon simulated to realistic exhaust systems.
More importantly, our generic strategy offers a novel and efficient
avenue to design ultrastable hetereogeneous catalysts with diverse
metal and support compositions and architectures.
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