Carbon nitride materials include functional materials, and their chemical diversity and complexity are becoming increasingly appreciated. Heating of NH 4 SCN leads to a range of new carbon nitride compounds, which have been structurally characterized by single-crystal X-ray diffraction. Heating at ambient pressure to 175°C leads to guanidinium thiocyanate, H 6 CN 3 SCN (1), and when maintaining that temperature for about 12h a water-insoluble carbon nitride product is formed, which is a co-crystal between melamine and melamium thiocyanate, [H 6 C 3 N 6 ]·[H 10 C 6 N 11 ] + ·[SCN] - (2). In situ powder X-ray diffraction measurements of this material reveal a gradual transformation from (2), via two intermediate products, to a final melon-like end product. The first of these forms between 350 and 400°C, and is an adduct of melam and melamium thiocyanate, [H 9 C 6 N 11 ]·2[H 10 C 6 N 11 ] + ·2[SCN] - (3). The second forms between 400 and 480°C, and is identified as melem, 2,5,8-triamino-tri-s-triazine, H 6 C 6 N 10 (4). On heating of (2) in a sealed ampoule to 600°C, various crystals were obtained and six crystal structures were determined from the batch: 1,3,5-triazine-2,4,6-triamino, H 6 C 3 N 6 (5), 1,3,5-triazine-2,4-diamino, H 5 C 3 N 5 (6), 1,1′,3,3′,5,5′-triazine-2,2′,4,4′-tetraamino, H 8 C 6 N 10 (7), 2[H 6 C 3 N 6 ]·[H 10 C 6 N 11 ] + ·[SCN] - (8) and 2[H 6 C 3 N 6 ]·[H 7 C 3 N 6 ] + ·[SCN] - (9). Finally, a recrystallized decomposition product was found to be [H 6 C 3 N 6 ]·[H 7 C 3 N 6 ] + ·[SCN] - ·[H 2 O] (10).