A boron nitride–carbon composite derived from ammonia borane and ZIF-8 with promises for the adsorption of carbon dioxide

Abstract

In the present study, we report the synthesis, characterization and assessment of the carbon dioxide adsorption capacity of a composite made of boron nitride and carbon. The material is obtained through a two-step process. In the initial step, ammonia borane is introduced into the pores of a zeolitic imidazolate framework (ZIF-8) using a novel one-pot synthesis method. The ZIF-8 is formed in situ around the ammonia borane molecules, eliminating the need for an infiltration step. The successful confinement of ammonia borane within the ZIF-8 structure is verified through different characterization techniques (IR, XRD, TGA-DSC, and ¹¹B MAS NMR). In the second step, ZIF-8 containing confined ammonia borane is pyrolyzed. Ammonia borane acts as a precursor of boron nitride and the process results in a composite comprising carbon, boron and nitrogen. The composite was subsequently characterized and evaluated as a potential adsorbent for carbon dioxide. With a specific surface area of 56 m² g⁻¹, the composite demonstrates a CO₂ uptake of 1.94 mmol g⁻¹ (or 85.4 mg g⁻¹) when exposed to 1.5 bar of CO₂ at 30 °C. This value surpasses reported capacities of other boron nitride-based materials as CO₂ adsorbents. When comparing the CO₂ adsorption capacity in terms of the specific surface area, a significant enhancement is observed (34 × 10⁻³ mmol m⁻²). This suggests that the material provides more active sites for CO₂ adsorption, such as polarized B–C, B–N, and C–N bonds. This key factor may be even more important than having a large specific surface area. Therefore, the potential for developing new boron-based materials with enhanced CO₂ adsorption capacities lies in increasing both specific surface area and active sites.