Metal–Organic frameworks (MOFs) are increasingly
being investigated
for the synthesis of carbon-supported metal-based ultrafine nanoparticles
(UNPs). However, the collapse of the carbon framework and aggregation
of metal particles in the pyrolysis process have severely hindered
their stability and applications. Here, we report the synchronous
nucleation pseudopyrolysis of MOFs to confine Fe/FeOx UNPs in intact porous carbon nanorods (IPCNs), revealed by
in situ transmission electron microscopy experiments and ex situ structure
analysis. The pseudopyrolysis mechanism enables strong physical and
chemical confinement effects between UNPs and carbon by moderate thermal
kinetics and abundant oxygen defects. Further, this strong confinement
is greatly beneficial for subsequent chemical transformations to obtain
different Fe-based UNPs and excellent electrochemical performance.
As a proof of concept, the as-prepared FeSe UNPs in IPCNs show superior
lithium storage performance with an ultrahigh and stable capacity
of 815.1 mAh g–1 at 0.1 A g –1 and 379.7 mAh g–1 at 5 A g–1 for 1000 cycles.