Luminescent Porphyrinic Metal–Organic Frameworks for Oxygen Sensing: Correlation of Nanostructure and Sensitivity

Oxygen sensing capabilities of a series luminescent zirconium-based porphyrinic metal–organic frameworks (MOFs) (PCN-222, PCN-223, and PCN-224) have been investigated. Design experiments allowed identification the most sensitive material, PCN-224 MOF. In this luminescence in air is quenched by up to 7.3-fold with bimolecular quenching constant kq 56,000 Pa–1 s–1, which significantly above previously reported benchmark material same MOF type (kq 34,000 s–1). The oxygen sensitivity increases order PCN-222 < PCN-223 effective Stern–Volmer (SV) constants range 0.13 kPa–1 for PCN-222, 0.18 0.45 PCN-224-type materials. This effect attributed increase porphyrin–porphyrin separation these nanostructured materials that results fluorescence decay time thus probability event. Defects nanostructure also are important explain variations within MOFs type. Among investigated materials, those belonging were found be robust terms only little variation SV constants. analogues PCN utilize Pt(II) porphyrin as building block prepared. It shown synthetic protocols established metal-free systems can used metal complex. Analogous based on porphyrin, from Pt(II)PCN-222 (KSV 30 kPa–1) via Pt(II)PCN-223 40 Pt(II)PCN-224 87 kPa–1).