Simultaneous Production and Functionalization of Boron Nitride Nanosheets by Sugar‐Assisted Mechanochemical Exfoliation

Abstract

Due to their extraordinary properties, boron nitride nanosheets (BNNSs) have great promise for many applications. However, the difficulty of their efficient preparation and their poor dispersibility in liquids are the current factors that limit this. A simple yet efficient sugar‐assisted mechanochemical exfoliation (SAMCE) method is developed here to simultaneously achieve their exfoliation and functionalization. This method has a high actual exfoliation yield of 87.3%, and the resultant BNNSs are covalently grafted with sugar (sucrose) molecules, and are well dispersed in both water and organic liquids. A new mechanical force–induced exfoliation and chemical grafting mechanism is proposed based on experimental and density functional theory investigations. Thanks to the good dispersibility of the nanosheets, flexible and transparent BNNS/poly(vinyl alcohol) (PVA) composite films with multifunctionality is fabricated. Compared to pure PVA films, the composite films have a remarkably improved tensile strength and thermal dissipation capability. Noteworthy, they are flame retardant and can effectively block light from the deep blue to the UV region. This SAMCE production method has proven to be highly efficient, green, low cost, and scalable, and is extended to the exfoliation and functionalization of other two‐dimensional (2D) materials including MoS2, WS2, and graphite.

Construction of a Nanoporous Highly Crystalline Hexagonal Boron Nitride from an Amorphous Precursor for Catalytic Dehydrogenation

“…In the h-BN precursor,t he main peaks with abinding energy (BE) of 190.8 eV in the B1s and 398.5 eV in the N1s correspond to B À Nbonds.Inaddition, the B À Obond with BE = 192.3 eV and NÀCb ond with BE = 400.1 eV are also exhibited within the h-BN framework, and are in close agreement with the reported data. [13] Comparatively,t he crystalline h-BNNS after treatment by Mg powder only showed asignal of B À Nbonds with BE = 190.3 eV in B1s and BE = 397.9 eV in N1s,i ndicating that most of the residual carbon and oxygen elements from the starting materials were further removed during the heating process through combination with Mg, resulting in high-purity h-BN.The removal of oxygen atoms during the recrystallization process is also evidenced by the magic angle spinning (MAS) 11 Bsolid-state NMR spectroscopy ( Figure S3). In the 11 Bspectra of the h-BN precursor,a no bvious signal for BO 3 is shown at À0.72 ppm, which disappears in the crystalline h-BNNS.B oth the h-BN precursor and the crystalline h-BNNS exhibited 11 Bsignals at 10.2 ppm and 26.1 ppm, which is attributed to the BN 3 structure.…”

“…[2,6,7] Generally,t heir properties/ functionality can vary tremendously depending on their different structural characteristics,s uch as size,s urface area, thickness,crystal phase,defects,vacancies,e tc. Thet hickness of the h-BN materials (bulk vs.f ew layered) also had asignificant effect on their properties.Generally,few layered h-BNNS are preferred, which are mostly prepared via either as olid-phase mechanical method [13] or liquid-phase exfoliation. [11,12] Although both bulk h-BN and BNNT exhibited analogous product distributions,B NNT showed ar ate of propane consumption more than one order of magnitude higher than that of h-BN,p artially because of the higher surface area of BNNT (97 m 2 g À1 )relative to bulk h-BN (16 m 2 g À1 ), and thus as uperior mass transfer effect during the catalytic process.…”

“…[11,12] Although both bulk h-BN and BNNT exhibited analogous product distributions,B NNT showed ar ate of propane consumption more than one order of magnitude higher than that of h-BN,p artially because of the higher surface area of BNNT (97 m 2 g À1 )relative to bulk h-BN (16 m 2 g À1 ), and thus as uperior mass transfer effect during the catalytic process. Thet hickness of the h-BN materials (bulk vs.f ew layered) also had asignificant effect on their properties.Generally,few layered h-BNNS are preferred, which are mostly prepared via either as olid-phase mechanical method [13] or liquid-phase exfoliation. [14,15] Our group previously presented an efficient strategy for the scalable synthesis of few-layered h-BNNS using agas exfoliation of bulk h-BN in liquid N 2 .…”

2D Crystal–Based Fibers: Status and Challenges

“…Chen et al mixed cheap sucrose with h‐BN powder and then prepared 2D h‐BN crystals grafted with sucrose molecule by dry ball milling. The 2D crystals of functionalized h‐BN can be dispersed stably and uniformly in water and organic solvents by ultrasonication, which are suitable for further preparation of aerogel blocks, composite films and other macromaterials . The ball milling method is simple, robust, and efficient, however, it is not suitable for preparing 2D crystals with high activity, such as black phosphorus.…”

Construction of a Nanoporous Highly Crystalline Hexagonal Boron Nitride from an Amorphous Precursor for Catalytic Dehydrogenation

“…The thickness of the h‐BN materials (bulk vs. few layered) also had a significant effect on their properties. Generally, few layered h‐BNNS are preferred, which are mostly prepared via either a solid‐phase mechanical method or liquid‐phase exfoliation . Our group previously presented an efficient strategy for the scalable synthesis of few‐layered h‐BNNS using a gas exfoliation of bulk h‐BN in liquid N 2 .…”