Mechanistic Insight into H 2 S‐Induced Fluorescence Quenching in a Robust Metal–Organic Framework

ABSTRACT The development of chemically robust sorbents capable of integrating capture and optical sensing of toxic gas remains a major challenge. Herein, the ultramicroporous Zn(II)‐based metal‐organic framework, MFM‐520, has been investigated for the adsorption and luminescent detection of H 2 S. Breakthrough measurements at 298 K and 1 bar show a reversible H 2 S uptake of 3.91 mmol g −1 , while powder X‐ray diffraction confirms full retention of crystallinity after adsorption. Solid‐state photoluminescence experiments reveal a pronounced, selective fluorescence turn‐off response to H 2 S in the gas phase, with a limit of detection of 6.13 ppm. Time‐resolved spectroscopy shows a decrease in the excited‐state lifetime upon H 2 S adsorption, indicating enhanced non‐radiative decay pathways. In situ DRIFTS measurements indicate that H 2 S interacts with MFM‐520 through supramolecular interactions. The combined adsorption, structural, and spectroscopic analyses establish that fluorescence quenching arises from reversible, confinement‐amplified modulation of ligand‐centered excited‐state dynamics. These results highlight how coordinatively saturated Zn(II) nodes within ultramicroporous environments can couple chemical stability with selective luminescent gas sensing.