Direct conversion of N₂ and O₂: status, challenge and perspective

As key components of air, nitrogen (N₂) and oxygen (O₂) are the vital constituents of lives. Synthesis of NO₂, and C-N-O organics direct from N₂ and O₂, rather than from an intermediate NH₃ (known as the Haber-Bosch process), is tantalizing. However, the extremely strong N≡N triple bond (945 kJ mol^-1) and the nonpolar stable electron configuration of dinitrogen lead to its conversion being extensively energy demanding. The further selective synthesis of high-value C-N-O organics directly from N₂, O₂ and C-containing molecules is attractive yet greatly challenging from both scientific and engineering perspectives. Enormous efforts have been dedicated to the direct conversion of N₂ and O₂ via traditional and novel techniques, including thermochemical, plasma, electrochemical, ultrasonic and photochemical conversion. In this review, we aim to provide a thorough comprehension of the status and challenge of the direct conversion of N₂, O₂ and C-containing molecules (particularly N₂ and O₂). Moreover, we will propose some future perspectives to stimulate more inspiration from the scientific community to tackle the scientific and engineering challenges.