Using boric acid (H3BO3) as a boron source and zinc acetate [Zn(Ac)(2)] as a release chemical, various boron nitride nanosheets (BNNSs) are synthesized in the presence of ammonia (NH3). The structures of the BNNSs are tuned by changing the preparation procedures and the mole ratios of H3BO3 and Zn(Ac)(2). The results indicate that Zn(Ac)(2) is an excellent template and release agent for the formation of BNNSs owing to the suitable decomposition temperature, the easy reduction of zinc oxide (ZnO) in NH3, and the relatively low boiling point of zinc (Zn). As two-dimensional layered materials, all of the prepared BNNSs can reduce the friction coefficient (FC) of pure water, and the large-area and thick nanosheets show better tribological performances than the small-area and thin nanosheets, possibly as a result of the weakened mechanical strength at the reduced sizes.