Rational
design of metal–organic frameworks (MOFs) into
ultrathin two-dimensional (2D) nanosheets with controllable thickness
is significantly attractive but is also a significant challenge. Herein,
the authors report, for the first time, the synthesis of ultrathin
2D nickel-based MOF nanosheets with a thickness of only about 2 nm
via a ligand-assisted controllable growth strategy, which cannot be
acquired from the exfoliation of their bulky counterparts or the conventional
hydrothermal method. The correlation between 2D nanosheets and crystal
growth preference was demonstrated through a judicious choice of a
specific [Ni(BIP)(p-BDC)(H2O)2]
n
framework (BIP = (3,5-bis(1-imidazoly)pyridine), p-H2BDC = terephthalic acid) to underlie the
geometry of the resultant morphology. Under the modulation by the
dosage of terephthalic acid through a corrosion–dissolution–coordination
process, the nanosheets of Ni-MOFs with a controllable thickness can
be tuned to 50 and 100 nm. Ultrathin 2D Ni-MOF nanosheet-derived N-doped
Ni@carbon exhibits a satisfactory electrocatalytic performance with
a small overpotential of 170 mV to achieve a current density of 10
mA cm–2, much outperforming the bulk Ni-MOF and
the most reported non-noble-metal oxygen evolution reaction electrocatalysts
to date. It is believed that this ligand-assisted controllable growth
strategy represents a novel and simple path to prepare high-performance
MOF-based electrocatalysts for wide applications.