Recent Advances in 1,8-Naphthalimide-Based Supramolecular Gels (2020–2026)

Naphthalimide (NI) derivatives constitute attractive building blocks for the construction of fluorescent supramolecular gels owing to their structural versatility, remarkable photophysical properties, and ability to participate in non-covalent interactions. These properties prompted us to write this review, that provides a focused overview of the representative advances reported between 2020 and 2026 in NI-based supramolecular gels, covering the evolution from low-molecular-weight organogelators and metallogels to peptide-based and water-compatible hydrogels. Particular attention is paid to the influence of molecular design on self-assembly and gelation, including the contribution of hydrogen bonding, π–π stacking, metal coordination, and other intermolecular interactions to the formation of fibrillar supramolecular networks. The close relationship between aggregation and the photophysical response of the NI chromophore is also discussed, highlighting phenomena such as aggregation-induced and aggregation-enhanced emission and gelation-induced fluorescence enhancement. These properties have enabled the development of stimuli-responsive materials displaying fluorescence modulation and gel–sol or gel–gel transitions, particularly in response to metal ions and chemical stimuli. Recent studies also further demonstrate a transition toward more complex functional systems, including fluorescent peptide hydrogels and thixotropic materials with potential biomedical applications. The main applications developed during this period, ranging from chemical sensing to smart fluorescent materials, bioimaging, and biomedical systems, are critically analyzed. Finally, current limitations and future opportunities for NI-based gels are discussed, with particular emphasis on the development of red and near-infrared emissive systems and advanced soft photonic materials.