Template-free synthesis of water-vapor stable porous 3D boron nitride

Abstract

Due to its high thermal stability, dipolar structure, and easy synthesis porous boron nitride is a promising material in adsorption, catalysis, and gas storage. However, recent investigations showed that micro-mesoporous boron nitride is highly water-susceptible and reacts quickly with water to boron oxide and ammonia. Key parameters such as boron oxide content, crystallinity, and porosity primarily influence the water stability. Previous studies indicate that the synthesis of boron nitride without any microporosity could lead to a water-vapor stable product. Thus, this work pursues the template-free synthesis of solely meso-macroporous boron nitride. In order to achieve this, the influence of different nitrogen flow rates on the porosity of boron nitride was investigated. In addition, a pre-heating step was introduced which led to the successful synthesis of a meso-macroporous material. By varying the precursor ratio up to urea to boric acid 4–1, the porosity of the product was increased up to a BET surface area of 361 m2 g-1. To analyse the water stability, water-vapor adsorption was used. This enabled us to demonstrate the successful synthesis of highly water-vapor stable porous boron nitride.