For each of the well-known co-crystal formers, isonicotinamide and nicotinamide, a new polymorph, obtained during attempted co-crystallisation experiments, has been fully characterized and its stability relationship with previously reported forms established.

This paper examines chromic metal–organic frameworks, an important class of materials owing to their applications in several technological fields. These materials change their absorption spectra upon application of an external stimuli such as heat, pressure, light etc. This review explores recent advancements in photochromic, thermochromic, solvatochromic, and piezochromic metal–organic frameworks (MOFs). Emphasis is directed towards the design of chromic MOFs as well as the mechanisms associated with the colour change upon application of an external stimulus. Compared to traditional organic and inorganic materials, MOFs show exceptional chromic behavior as they can be fine-tuned to tailor the desired properties.