Formation of graphene oxide nanocomposites from carbon dioxide using ammonia borane

To efficiently recycle CO ₂ to economically viable products such as liquid fuels and carbon nanomaterials, the reactivity of CO ₂ is required to be fully understood. We have investigated the reaction of CO ₂ with ammonia borane (AB), both molecules being able to function as either an acid or a base, to obtain more insight into the amphoteric activity of CO ₂. In the present work, we demonstrate that CO ₂ can be converted to graphene oxide (GO) using AB at moderate conditions. The conversion consists of two consecutive steps: CO ₂ fixation (CO ₂ pressure <3 MPa and temperature <100 °C) and graphenization (600-750 °C under 0.1 MPa of N ₂). The first step generates a solid compound that contains methoxy (OCH ₃), formate (HCOO), and aliphatic groups, while the second graphenization is the pyrolysis of the solid compound to produce graphene oxide-boron oxide nanocomposites, which have been confirmed by micro-Raman spectroscopy, solid-state ¹³C and ¹¹B magic angle spinning-nuclear magnetic resonance (MAS NMR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Our observations also show that the mass of solid product in CO ₂ fixation process and raw graphene oxide nanocomposites is twice and 1.2 times that of AB initially charged, respectively. The formation of aliphatic groups without using metal-containing compounds at mild conditions is of great interest to the synthesis of various organic products starting from CO ₂.