Luminescent MOFs constructed by using butterfly-like AIE ligands

In this work, a series of butterfly-like isomers named oxacalix[2]naphthalene[2]pyrazine (ONP) were conveniently synthesized by a one-step catalyst-free reaction in a facile manner, and they exhibit typical characteristics of aggregation-induced emission (AIE). The mechanism study shows that restriction of intramolecular vibration (RIV) is the reason for their AIE properties. The pyrazine groups endow ONP molecules with good coordination ability, which makes them ideal ligands for constructing metal-organic frameworks (MOFs). Thus, three ONP-based luminescent MOFs were constructed, and they exhibit intense emission with lifetimes in the order of microseconds. More importantly, different ONP isomers have different binding capacities, and thus only one kind of MOF can be obtained even when using an isomer mixture of ONP ligands. This result suggested that the conformation of ONPs is an important determining factor for their application as bridging ligands. This work not only reports a series of new RIV-type AIEgens, but also offers a new platform for the construction of luminescent MOFs.