Crystalline structural intermediates of a breathing metal-organic framework that functions as a luminescent sensor and gas reservoir.

A rod-packing, breathing MOF (1), with two crystalline structural intermediates (1 a and 1 b; H(2) btca = benzotriazole-5-carboxylic acid) has been investigated. An underlying net approach for analyzing possible breathing MOFs, and a set of geometric parameters that can quantitatively describe such a breathing structural feature, are suggested. The 3D luminescent MOF is a promising candidate for specific sensors with exceptional sorption capacity.