Amine-Templated N,O-Linked Co(II)-MOF with hxl Topology for “Turn-On” Detection of Tumor Biomarker GSH and Industrial Toxicant HCHO: A Dual-Target Approach

Fluorescent functional materials, particularly luminescent metal–organic frameworks (LMOFs), have been central to material science research over the past decade. Herein, we report a Co-MOF [Co(phen)(5-aipa)]_∞ (phen: 1,10-phenanthroline, 5-aipa: 5-aminoisophthalic acid), synthesized solvothermally, for luminescence-based, recyclable, “turn-on” detection of “tumor biomarker” glutathione (GSH), and industrial pollutant formaldehyde (FA). Sophisticated characterizations, including XRD, XPS, TGA, FESEM, FT-IR, and Hirshfeld analysis, demonstrate high phase purity, thermal stability, robustness, presence of π–π stacking, and weak H-bonding in the framework. The MOF shows low detection limits for GSH (60.37 nM) and FA (9.77 μM) with fast response times (25 s for GSH, <2 min for FA). Biomarker GSH was detected in complex biological samples, including fetal bovine serum, vegetable, and human urine, with recovery rates between 81% and 89%. A smartphone-assisted GSH-sensing platform was proposed via RGB color variations of several sensor-analyte adducts. A 5-input, 4-output molecular logic gate was also demonstrated based on the sensor's spectroscopic response to varying GSH concentrations. FA detection was extended to fish, meat, and wastewater samples, with recoveries of 91–107%. DFT calculations revealed that analyte interactions restricted photo-induced electron transfer in the MOF, enhancing fluorescence phenomenon. These findings open new possibilities for MOF-based sensor technologies.