Since the recent discovery of the template-free synthesis of porous boron nitride, research on the synthesis and application of the material has steadily increased. Nevertheless, the formation mechanism of boron nitride is not yet fully understood. Especially for the complex precursor decomposition of urea-based turbostratic boron nitride (t-BN), a profound understanding is still lacking. Therefore, in this publication, we investigate the influence of different common pre-heating temperatures of 100, 200, 300, and 400 degrees C on the subsequent properties of t-BN. We show that the structure and porosity of t-BN can be changed by preheating, where a predominantly mesoporous material can be obtained. Within these investigations, the sample BN-300/2 depicts the highest mesopore surface area of 242 m(2) g(-1) with a low amount of micropores compared to other BNs. By thermal gravimetric analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy, valid details about the formation of intermediates, types of chemical bonds, and the generation of t-BN are delivered. Hence, we conclude that the formation of a mesoporous material arises due to a more complete decomposition of the urea precursor by pre-heating.

Porous boron nitrides possess beneficial properties such as high thermal and chemical stability which are critical for applications in adsorption processes. In order to assess possible fields of applications, trace-level adsorption isotherms of different hydrocarbons on two synthesized porous boron nitrides and two commercial activated carbons are compared. By normalizing the adsorptive loadings on the micropore surface area, superior adsorption performances of the BN materials on polar and aromatic adsorptives with up to 50% higher loadings compared to the activated carbons can be shown. Nonpolar adsorptives, on the other hand, feature higher specific loadings on the activated carbon. Consequently, the size of the micropore surface appears to be decisive for nonpolar adsorptives, while the higher polarity of the boron nitrides is the dominant influencing factor for the adsorption of polar and aromatic components. For an energetic study of the adsorbents, calorimetric experiments were performed to identify and discuss adsorbent-adsorptive interactions. While the initial heat of adsorption of the nonpolar n-hexane is lower on the boron nitride than on the activated carbon due to a less favorable spatial arrangement, toluene shows comparable values on both adsorbent classes and the polar acetone shows higher values on the polar boron nitride. Considering technical applications in adsorption technology, the thermal stability of the boron nitrides is investigated using spontaneous ignition temperatures and points of initial oxidation. Here, the porous boron nitrides with oxidation temperatures above 900 °C show about 400 °C higher values and thus a significantly higher thermal stability.

Porous boron nitride is promoted as a promising material for the removal of dyes, antibiotics, and metal ions from wastewater, despite its known hydrolytic instability. This review discusses its application in water critically.

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 m ² 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.