Porous boron nitride nanosheets via pyrolysis of melamine phosphate and borate assembly for water purification

Development of porous micro-nanomaterials with excellent physical and chemical stability as adsorbents for effective water cleanup still has huge practical implications. Here, hierarchically porous boron nitride nanosheets (BNNSs) with abundant active groups (-OH and –NH 2 ) and defective structures were prepared via the incorporation of phosphoric acid into melamine borate (M·2B) to form a melamine phosphate and borate assembly and subsequent pyrolysis . Phosphoric acid can interact with melamine through hydrogen bonding , which not only changes the micromorphology of porous BN materials but also regulates their chemical compositions and bonding states. The resulting porous BNNSs show a specific surface area as high as 1477.923 m 2 /g and a large pore volume . Encouraged by these characteristics, the resulting porous BNNSs exhibit remarkable adsorption capabilities for methylene blue (MB) in alkaline solution up to 750 mg/g and oxytetracycline (OTC) in acidic solution up to 128 mg/g. Additionally, they have excellent cyclic adsorption performance, suggesting a high practical value in wastewater purification. Therefore, this work not only presents the practical application of porous BNNSs in sewage treatment but also provides a designing scheme for preparing variety micro- and nano-BN materials by regulating and controlling the transformation of melamine salts.