Here,
the effect of morphology on the electrocatalytic activity
of metal–organic framework (MOF) was investigated. Post synthetic
gold (Au) insertion was done into hollow PCN-222 (HPCN-222) and solid
PCN-222 (SPCN-222) frameworks by a simple hydrothermal method. The
crystalline nature, chemical composition, and morphologies of the
synthesized MOFs were characterized by PXRD, XPS, and TEM. Electrochemical
characterizations were done by cyclic voltammetry and electrochemical
impedance spectroscopy. The excellent electrocatalytic activity of
highly small-sized Au(0) with the enhancement of electrical conductivity
through a hopping mechanism combined with a hollow structure and high
surface area in the HPCN-222 MOF hugely alters the electrochemical
properties. Overall, a better electrocatalytic surface area, charge
transfer coefficient, and catalytic activity were generated at the
modified electrode. The hollow structure MOF showed better electrocatalytic
activity than solid structured MOF. The AuHPCN-222 modified glassy
carbon electrode (AuHPCN-222/GCE) electrochemical sensor was employed
for the analytical analysis of estradiol (ED) in an optimum experimental
condition. AuHPCN-222 showed selective and better electrocatalytic
activity toward ED than GCE. The differential pulse voltammetric measurements
by the fabricated sensor showed two linear determination ranges for
ED; those are 0.01–1 and 1–220 μM. The measured
limit of detection (m-LOD) was found to be 0.5 nM with the highest
sensitivity of 2.2 μA μM cm–2. The analytical
performances for the detection of ED in human urine and serum samples
were done with reasonable recoveries (98%–103%) using the standard
addition method. Also, the sensor showed better reproducibility and
repeatability with stability.