Flexible, Luminescent Metal–Organic Frameworks Showing Synergistic Solid‐Solution Effects on Porosity and Sensitivity

Mixing molecular building blocks in the solid solution manner is a valuable strategy to obtain structures and properties in between the isostructural parent metal–organic frameworks (MOFs). We report nonlinear/synergistic solid‐solution effects using highly related yet non‐isostructural, phosphorescent Cu I triazolate frameworks as parent phases. Near the phase boundaries associated with conformational diversity and ligand heterogeneity, the porosity (+150 %) and optical O 2 sensitivity (410 times, limit of detection 0.07 ppm) can be drastically improved from the best‐performing parent MOFs and even exceeds the records hold by precious‐metal complexes (3 ppm) and C 70 (0.2 ppm).