On‐Demand Preparation of Boron Nitride Nanosheets for Functional Nanocomposites

Abstract Boron nitride nanosheets (BNNSs) have garnered significant attention across diverse fields; however, accomplishing on‐demand, large‐scale, and highly efficient preparation of BNNSs remains a challenge. Here, an on‐demand preparation (OdP) method combining high‐pressure homogenization and short‐time ultrasonication is presented; it enables a highly efficient and controllable preparation of BNNSs from bulk hexagonal boron nitride ( h ‐BN). The homogenization pressure and number of cycles are adjusted, and the production efficiency and yield of BNNSs reach 0.95 g g −1 h −1 and 82.8%, respectively, which significantly exceed those attained by using existing methods. The universality of the OdP method is demonstrated on h ‐BN raw materials of various bulk sizes from various producers. Furthermore, this method allows the preparation of BNNSs having specific sizes based on the final requirements. Both simulation and experimental results indicate that large BNNSs are particularly suitable for enhancing the thermal conductivity and electrical insulation properties of dielectric polymer nanocomposites. Interestingly, the small BNNS‐filled photonic nanocomposite films fabricated via the OdP method exhibit superior daytime radiative cooling properties. Additionally, the OdP method offers the benefits of low energy consumption and reduced greenhouse gas emissions and fossil energy use. These findings underscore the unique advantages of the OdP method over other techniques for a high‐efficiency and controllable preparation of large BNNSs.