Scalable production of high-quality boron nitride nanosheets via a recyclable salt-templating method

Hexagonal boron nitride nanosheets (h-BNNSs) have attracted intensive attention due to their excellent physicochemical properties and potential industrial applications. Numerous studies have been explored for the mass production of h-BNNSs. However, their high energy cost and low efficiency remain huge challenges. Here we demonstrate a recyclable, scalable and green method for h-BNNS production with a high efficiency up to 88.4%. In this strategy, B2O3, the most common but rarely used boron compound, was utilized as a boron precursor and nitrided at relatively low temperatures. In this process, NaCl crystals served as recyclable and sacrificial templates so that hollow-structured h-BNNSs were obtained. DFT calculations revealed that NaCl facilitates the adsorption of B2O3 and benefits the formation of h-BNNSs. The NaCl template could be recycled via a simple rinsing and re-precipitation process. Moreover, we demonstrate the thermal application of the as-synthesized h-BNNSs in PVA-based composite materials, which exhibit high in-plane thermal conductivity up to 8.35 W mK−1 with 15.85 wt% filling while reducing the coefficients of thermal expansion.