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 -NH2) and defective structures were prepared via the incorporation of phosphoric acid into melamine borate (M & sdot;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 m2/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 nanoBN materials by regulating and controlling the transformation of melamine salts.