High-pressure synthesis of a polymeric N3H2 solid stabilized by hydrogen bonds

Abstract Polymeric nitrogen represents a long-sought class of high energy density materials, in which single-bonded nitrogen networks release large amounts of energy upon decomposition to molecular N 2 . However, polymeric nitrogen allotropes require extreme pressures to synthesize and cannot be recovered at ambient conditions due to surface instabilities. Hydrogen has been proposed as a key element to stabilize such frameworks, yet polymeric nitrogen–hydrogen solids have until now remained the realm of theoretical calculations. Here, we report the high-pressure synthesis of polymeric N 3 H 2 at 134(3)–139(1) GPa from N 2 –H 2 mixtures. Synchrotron single-crystal X-ray diffraction, Raman spectroscopy and first-principles calculations reveal a fully single-bonded framework of 1-dimensional chains of N 6 rings, each decorated by four H atoms. The chains of N 6 H 4 units are cross-linked through hydrogen bonds. Employing modern synchrotron sources, hydrogen positions are directly resolved from diffraction data at 139(1) GPa. At ambient conditions, N 3 H 2 exhibits an estimated energy of decomposition of 7.98 kJ/g, highlighting hydrogen-stabilized polymeric nitrogen as a promising class of energetic materials.