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Abstract The development of large pore single‐crystalline covalently linked organic frameworks is critical in revealing the detailed structure‐property relationship with substrates. One emergent approach is to photo‐crosslink hydrogen‐bonded molecular crystals. Introducing complementary hydrogen‐bonded carboxylic acid building blocks is promising to construct large pore networks, but these molecules often form interpenetrated networks or non‐porous solids. Herein, we introduced heteromeric carboxylic acid dimers to construct a non‐interpenetrated molecular crystal. Crosslinking this crystal precursor with dithiols afforded a large pore single‐crystalline hydrogen‐bonded crosslinked organic framework H_COF‐101. X‐ray diffraction analysis revealed H_COF‐101 as an interlayer connected hexagonal network, which possesses flexible linkages and large porous channels to host a hydrazone photoswitch. Multicycle Z/E‐isomerization of the hydrazone took place reversibly within H_COF‐101, showcasing the potential use of H_COF‐101 for optical information storage. 

BF 2 -based fluorophores, such as the well-known BODIPY (4,4-difluoro-4-bora-3 a ,4 a -diaza- s -indacene) dye, are prevalently used in diverse research areas ( e.g. , bioimaging and chemosensing) as they exhibit promising features including high quantum yields, fine-tuned absorption and emission spectra as well as good photostability and biocompatibility. While BODIPY dyes are most commonly used in such applications, other BF 2 -based fluorophores, such as BOPHY (bis(difluoroboron)-1,2-bis((1 H -pyrrol-2-yl)methylene)hydrazine – which possess their own characteristic features – are rising in popularity and are being used in a range of applications spanning from molecular sensors to photosensitizers for solar cells. This review examines select examples of BOPHY dyes to highlight the progression of their development while detailing their syntheses and photophysical properties including structure–property relationships. Applications of a number of substituted BOPHYs made by the methods described in this review are also presented. 

The spatiotemporal control over the structure of nanoparticles while monitoring their localization in tumor cells can improve the precision of controlled drug release, thus enhancing the efficiency of drug delivery. Here, we report on a photochromic nanoparticle system ( LSNP ), assembled from fluorescent bistable hydrazone photoswitch-modified amphiphilic copolymers. The intrinsic emission of the hydrazone switch allows for the visualization of particle uptake, as well as their intracellular distribution. The Z → E photoswitching of the hydrazone switch within the nanoparticle leads to the expansion of the nanoparticles ( i.e. , drug release) accompanied by emission quenching, the degree of which can function as an internal indicator for the amount of drug released. The bistability of the switch enables the kinetic trapping of particles of different sizes as a function of irradiation time, and allows for the exhibition of light-dependent cell cytotoxicity in MDA-MB-231 cells using LSNP loaded with doxorubicin.