Strong Second-Harmonic Generation Induced by a Triphenylamine-Based Bismuth–Organic Framework for Photocatalytic Activity Enhancement

Taking
advantage of the well-defined geometry of metal centers
and highly directional metal–ligand coordination bonds, metal–organic
frameworks (MOFs) have emerged as promising candidates for nonlinear
optical (NLO) materials. In this work, taking a photoresponsive carboxylate
triphenylamine derivative as an organic ligand, a bismuth-based MOF,
Bi-NBC, NBC = 4′,4‴,4‴″-nitrilotris(([1,1′-biphenyl]-4-carboxylic
acid)) is obtained. Structure determination reveals that it is a potential
NLO material derived from its noncentrosymmetric structure, which
is finally confirmed by its rarely strong second harmonic generation
(SHG) effect. Theoretical calculations reveal that the potential difference
around Bi atoms is large; therefore, it leads to a strong local built-in
electric field, which greatly facilitates the charge separation and
transfer and finally improves the photocatalytic performance. Our
results provide a reference for the exploration of MOFs with NLO properties.