Hierarchically porous boron nitride foams for multifunctional bulk adsorbents.

[Display omitted] • The formation mechanism of porous BN foams (BNFs) is studied in-depth. • BNFs exhibit hierarchical pore structures and robust mechanical integrity. • BNFs possess high adsorption capacities for CO 2 , liquid nitrogen and naphthalene. • BNFs are designed as permeation-separation and filtration-adsorption columns. Boron nitride (BN) bulk adsorbents replace their powder ones, which indeed make up for many shortcomings of BN's powders in practical adsorption application and become the most promising BN-based multifunctional adsorption materials. However, the difficulty of synthesis greatly limits their development. Here, we prepare a series of highly porous BN foams (BNFs), via a facile compression forming and controllable high-temperature nitriding method. The BNFs have hierarchical pore characteristics, including abundant micropores (~40 vt.%), and various mesopores and macropores (~60 vt.%), while they possess a robust three-dimensional integrality with maximum compression strength up to ~ 2.2 MPa. These properties make the BNFs kinds of desired bulk adsorbents for application in advanced multifunctional adsorption. Firstly, they can capture various gas molecules, including ultrahigh CO 2 capacities of ~ 3.05 mmol/g (0 °C) and ~ 1.75 mmol/g (25 °C), naphthalene of ~ 155 wt% (80 °C) and 89 wt% (20 °C), and liquid nitrogen quantity of ~6.6-times weight of their own weight. In addition, the BNFs with a well hydrophobic-lipophilic surface exhibit remarkable adsorption for a wide range of organic reagents and oils, up to very high capacity of 600–1830 wt%, and show high-end permeation-separation and filtration-adsorption application in oil–water systems. Moreover, as a kind of static block adsorbents, the BNFs also have outstanding pollutant adsorption performances for S 8 and Li 2 S x in organic solvents, and the Ni(II) ions and methylene blue molecules in water. We believe that our new BNFs materials will be of great significance to lead the BN-based bulk adsorbents for continuous application in more sophisticated fields. [ABSTRACT FROM AUTHOR]