Cobalt MOF–Starbon Hybrids for Synergistic Chemosensing and Adsorption of Tetracycline

Pervasive tetracycline (TC) residues underscore the necessity
for
precise monitoring and efficient remediation. Starbon features a hierarchical
architecture and rich surface functionality to support sensing and
adsorption applications. Starbon has been extensively studied with
metal oxides, but its integration with metal–organic frameworks
(MOFs) for chemosensing and adsorption remains largely unexplored.
The current study reports the synthesis of a novel MOF (PUC-13) and
its composite with an S-350 starbon designated as SPU-10. SPU-10 was
employed as a dual-functional chemosensor for tetracycline recognition
and capture. A comprehensive suite of characterization methods was
used to meticulously examine and validate the structural framework,
surface characteristics, and thermal resilience of the composite.
Mechanistic understanding of sensing and adsorption behaviors was
reinforced through integrated spectroscopic analyses and surface characterization
techniques. The developed system showcases adaptive capabilities in
detecting tetracycline, reflected by a high Stern–Volmer quenching
constant (Ksv = 0.62 × 106 M–1) along with excellent adsorption performance
(98.2% removal efficiency). It exhibits a substantially maximum capacity
of adsorption (qmax) of 112.21 mg g–1. A notably low limit of detection, i.e., 0.35 μM,
underscores the remarkable sensitivity and selectivity of the SPU-10
nanocomposite. Smartphone-assisted on-site monitoring was also carried
out to validate the detection limit (LOD) for tetracycline. Pertaining
to a surface area of 39.53 m2 g–1, the
material exhibits a pseudo-second-order kinetic profile and aligns
closely with the Langmuir adsorption isotherm, indicating monolayer
coverage of tetracycline molecules. Mechanistic exploration through
X-ray Photoelectron Spectroscopy (XPS), time-resolved fluorescence
spectroscopy, and ζ-potential analysis provided crucial insight
into both detection and adsorption pathways. Initially, tetracycline
binds to the adsorbent via chemisorption followed by multilayer physisorption.
Static interactions and the inner filter effect (IFE) primarily govern
the fluorescence quenching of SPU-10. Recyclability was retained over
four successive cycles, and the real-world applicability was validated
in milk and water matrices.