Suppressing Room-Temperature Carrier Self-Trapping by an Ultrastable Lead Iodide Ortho-Dicarboxylate Hybrid

Lead
halide hybrids are a potentially promising class of photocatalysts
due to their excellent photophysical properties. However, carrier
self-trapping and intrinsic instability remain two significant challenges
for their widespread application. Herein, to address both issues,
we employ the coordination chemistry strategy to utilize an ortho-dicarboxylate
ligand for the synthesis of a layered coordination architecture consisting
of flat two-dimensional (2D) [Pb2I]3+ sheets.
The resultant planar and coordinative configuration effectively mitigates
carrier self-trapping at room temperature while exhibiting high structural
robustness to (photo)chemical conditions. Variable-temperature and
ultrafast transient photophysical studies elucidate the thermally
activated carrier detrapping dynamics, achieving a remarkable carrier
mobility of approximately 2.77 cm2 V–1 s–1. Notably, our material demonstrates substantially
enhanced photocatalytic efficiency in benzylic C(sp3)-H
oxidation compared with both the (001) layered perovskite and the
coordination polymer with self-trapped carriers. Density functional
theory calculations further confirm our experimental findings, indicating
that the adsorption and activation of ethylbenzene favor in-sheet
I– sites over out-of-sheet I– sites.
This study reveals the key importance of coordination chemistry in
structural-property modulation of lead halide hybrids while retaining
high stability.