Production of biocompatible and stable porous materials, e.g., boron nitride, exhibiting tunable and enhanced porosity is a prerequisite if they are to be employed to address challenges such as drug delivery, molecular separations, or catalysis. However, there is currently very limited understanding of the formation mechanisms of porous boron nitride and the parameters controlling its porosity, which ultimately prevents exploiting the material's full potential. Herein, we produce boron nitride with high and tunable surface area and micro/mesoporosity via a facile template-free method using multiple readily available N-containing precursors with different thermal decomposition patterns. The gases are gradually released, creating hierarchical pores, high surface areas (>1900 m/g), and micropore volumes. We use 3D tomography techniques to reconstruct the pore structure, allowing direct visualization of the mesopore network. Additional imaging and analytical tools are employed to characterize the materials from the micro- down to the nanoscale. The CO uptake of the materials rivals or surpasses those of commercial benchmarks or other boron nitride materials reported to date (up to 4 times higher), even after pelletizing. Overall, the approach provides a scalable route to porous boron nitride production as well as fundamental insights into the material's formation, which can be used to design a variety of boron nitride structures.

Porous boron nitride is gaining significant attention for applications in molecular separations, photocatalysis, and drug delivery. All these areas call for a high degree of stability (or a controlled stability) over a range of chemical environments, and particularly under humid conditions. The hydrolytic stability of the various forms of boron nitride, including porous boron nitride, has been sparingly addressed in the literature. Here, we map the physical-chemical properties of the material to its hydrolytic stability for a range of conditions. Using analytical, imaging and spectroscopic techniques, we identify the links between the hydrolytic instability of porous boron nitride and its limited crystallinity, high porosity as well as the presence of oxygen atoms. To address this instability issue, we demonstrate that subjecting the material to a thermal treatment leads to the formation of crystalline domains of h-BN exhibiting a hydrophobic character. The heat-treated sample exhibits enhanced hydrolytic stability, while maintaining a high porosity. This work provides an effective and simple approach to producing stable porous boron nitride structures, and will progress the implementation of the material in applications involving interfacial phenomena.

Boron nitride (BN) has applications in a number of areas: it can be used as lubricant, as insulating thermoconductive filler or UV-light emitter. BN can also capture large amounts of hydrocarbons and gaseous molecules, provided that it exhibits a porous structure. This porous structure also enables its application as a drug-delivery nanocarrier. Little if anything is known on controlling the porosity of BN, even though it has tremendous implications in terms of adsorption performance and drug delivery properties. To address * Corresponding Author: Camille Petit, camille.petit@imperial.ac.uk M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 this aspect, we provide for the first time an in-depth investigation of the effects of the synthesis conditions on the formation of porous BN. The material was also tested for CO 2 capture. We found that the intermediate preparation is of paramount importance and can in fact be used to tune the porosity of BN. Owing to a combination of spectroscopic and thermal analyses, we attributed this phenomenon to the variation of the thermal decomposition pattern of the intermediates. The most microporous BN produced was able to capture CO 2 while not retaining N 2 . Overall, this study opens the route for the design of well-controlled porous BN structures to be applied as adsorbents and drug-delivery carriers.

Hierarchically porous carbon foams were produced by carbonization of hypercrosslinked polymerized high internal phase water-in-styrene/divinylbenzene emulsions (HIPEs). The hypercrosslinking of these poly(ST-co-DVB)HIPEs was achieved using a dimethoxymethane external crosslinker to ‘knit’ together aromatic groups within the polymers using FriedelCrafts alkylation. By varying the amount of divinylbenzene (DVB) in the HIPE templates and subsequent polymers, the BET surface area and micropore volume of the hypercrosslinked analogues can be varied systematically, allowing for the production of carbon foams, or ‘carboHIPEs’, with varied surface areas, micropore volumes and pore-size distributions. The carboHIPEs retain the emulsion-templated macropores of the original polyHIPE, display excellent electrical conductivities and have surface areas of up to 417 m2/g, all the while eliminating the need for inorganic templates. The use of emulsion templates allows for pourable, mouldable precursors to designable carbonaceous materials

Porous boron nitride (BN) is structurally analogous to activated carbon. This material is gaining increasing attention for its potential in a range of adsorption and chemical separation applications, with a number of recent proof-of-concept studies on the removal of organics from water. Today though, the properties of porous BN—i.e., surface area, pore network, chemistry—that dictate adsorption of specific organics remain vastly unknown. Yet, they will need to be optimized to realize the full potential of the material in the envisioned applications. Here, a selection of porous BN materials with varied pore structures and chemistries were studied for the adsorption of different organic molecules, either directly, through vapor sorption analyses or as part of a water/organic mixture in the liquid phase. These separations are relevant to the industrial and environmental sectors and are envisioned to take advantage of the hydrophobic character of the BN sheets. The materials were tested and regenerated and their physical and chemical features were characterized before and after testing. This study allowed identifying the adsorption mechanisms, assessing the performance of porous BN compared to benchmarks in the field and outlining ways to improve the adsorption performance further.