Metal-organic frameworks (MOFs) are a chemically and topologically diverse family of materials composed of inorganic nodes and organic linkers bound together by coordination bonds. Presented here are two significant innovations in this field. The first is the use of a new coordination group, phenylene-1,4-bis(methylphosphinic acid) (PBPA), a phosphinic acid analogue of the commonly used terephtalic acid. Use of this new linker group leads to the formation of a hydrothermally stable and permanently porous MOF structure. The second innovation is the application of electron-diffraction tomography, coupled with dynamic refinement of the EDT data, to the elucidation of the structure of the new material, including the localization of hydrogen atoms.

Microbial colonization of biomedical devices is a recognized complication contributing to healthcare-associated infections. One of the possible approaches to prevent surfaces from the biofilm formation is antimicrobial photodynamic inactivation based on the cytotoxic effect of singlet oxygen, O(Δ), a short-lived, highly oxidative species, produced by energy transfer between excited photosensitizers and molecular oxygen. We synthesized porphyrin-based covalent organic frameworks (COFs) by Schiff-base chemistry. These novel COFs have a three-dimensional, diamond-like structure. The detailed analysis of their photophysical and photochemical properties shows that the COFs effectively produce O(Δ) under visible light irradiation, and especially three-dimensional structures have strong antibacterial effects toward Pseudomonas aeruginosa and Enterococcus faecalis biofilms. The COFs exhibit high photostability and broad spectral efficiency. Hence, the porphyrinic COFs are suitable candidates for the design of antibacterial coating for indoor applications.

Recent studies have unraveled the potential of octahedral molybdenum cluster complexes (Mo 6 ) as relevant red phosphors and photosensitizers of singlet oxygen, O 2 ( 1 Δ g ), for photobiological applications. However, these complexes tend to hydrolyze in an aqueous environment, which deteriorates their properties and limits their applications. To address this issue, we show that phenylphosphinates are extraordinary apical ligands for the construction of Mo 6 complexes. These new complexes display unmatched luminescence quantum yields and singlet oxygen production in aqueous solutions. More importantly, the complex with diphenylphosphinate ligands is the only stable complex of these types in aqueous media. These complexes internalize in lysosomes of HeLa cells, have no dark toxicity, and yet are phototoxic in the submicromolar concentration range. The superior hydrolytic stability of the diphenylphosphinate complex allows for conservation of its photophysical properties and biological activity over a long period, making it a promising compound for photobiological applications.

A zirconium metal-organic framework (MOF) PCN-222 was postsynthetically modified with diphenylphosphinic acid, resulting in an increased stability when activated from water and 4 times higher photosensitizing properties for singlet oxygen production. The phosphinic acid did not compromise the crystallinity of the MOF but made strong bonds with the zirconia secondary building units.