Understanding the Catalytic Sites in Porous Hexagonal Boron Nitride for the Epoxidation of Styrene

Abstract

Porous hexagonal boron nitride (ph-BN) nanosheets were synthesized via the combustion of boric acid and melamine by a pyrolysis method. The as-obtained ph-BN showed a high catalytic activity for the epoxidation of styrene using tert-butyl hydroperoxide as an oxidant. Both experimental and theoretical study demonstrated that the activity originated from the oxygen-containing functional groups at the edges of ph-BN. To further understand the mechanism for this catalytic behavior, in situ Fourier transform infrared spectroscopy in a diffusion reflectance model has been used to monitor the evolution of surface functional groups of ph-BN treated at different temperatures (50–800 °C). In this way, the active functional groups on the ph-BN have been identified. It was revealed that B–OH groups dehydrate to form B–O–B edges and are further oxidized to B–O–O–B type edges. B–OH is the main active site responsible for the epoxidation of styrene, while B–O–O–B edges have a similar activity. Finally, a plausible reaction pathway was proposed for the epoxidation of styrene on this metal-free catalyst based on the density functional theory calculation. A clear understanding of the catalytic sites for this metal-free catalyst and the functional group tuning strategy in this work may expand the BN-based material for various catalytic applications.

In Situ Generated Boron Peroxo as Mild Oxidant in Propane Oxidative Dehydrogenation Revealed by Density Functional Theory Study

“…In an earlier study of the boron-containing ODH catalytic system, we proposed the formation of >B–O–O–B< species at the zigzag edge, which was supported by the recent work of Fu et al that reported the oxidization of >B–OH groups to >B–O–O–B< . Recently Li et al reported boron–oxygen–nitrogen nanotubes (BONNTs) enriched with O–O species exhibited remarkable catalytic activity (a propane conversion of 64.4% with an olefin yield of 48.6% at 525 °C, 2.8 times that on boron nitrogen nanotubes).…”

“…Figure S4a shows the bond length variation of dioxygen O 13 −O 14 , which increased from 1.214 Å (IM1′) to 1.332 Å (IM2), indicating the activation of the dioxygen molecule. In view of the similar bond length of key chemical bonds in TS2 and IM2, e.g., for O 13 −O 14 (1.305 Å in TS2 vs 1.332 Å in IM2) and for O 13 −H 12 (1.043 Å in TS2 vs 0.993 Å in IM2), TS2 is a late transition state. Furthermore, the free-energy change of TS2 and IM2 is 32.66 and 31.44 kcal/mol, respectively, which is consistent with the Hammond postulate.…”

Perovskite LaSrCoFeO6 Oxide Enabled Visible Light Catalytic Aerobic Epoxidation of Styrene

“…This is the first example of employing LSCF oxides as superior visible‐light catalyst for epoxidation of styrene just using molecular oxygen as the oxidant. Relative with these (7.4∼37.5 mmol ⋅ g cat −1 ⋅ h −1 ) of the reported catalysts coupled with either oxygen or TBHP [6,20,33–36] (Table 1, entries 12–16), LSCF catalyst reported in this work shows the highest reaction rate of ∼50 mmol ⋅ g cat −1 ⋅ h −1 (Table 1, entry 7). Additionally, LSCF catalyst even shows the considerable catalytic performance under visible light compared with the activity of LSCF‐1.6 catalyst under ultraviolet light in our previous study [24] .…”

How to Tailor Porous Boron Nitride Properties for Applications in Interfacial Processes

“…Since then, other studies have reported using porous BN or hBN as an intrinsic heterogeneous catalyst or a catalyst support (Table ). , The dominant factor driving catalytic activity is the presence of O-containing groups and more specifically B–OH and B–O–O–B edge groups . For aerobic oxidative desulfurization, zinc (Zn) salt has been used as a template to develop porous BN, and the active site for the oxygen activation is composed of Zn nanoparticles and N-terminated edges …”