No abstract

The amalgamation of different disciplines is at the heart of reticular chemistry and has broadened the boundaries of chemistry by opening up an infinite space of chemical composition, structure, and material properties. Reticular design has enabled the precise prediction of crystalline framework structures, tunability of chemical composition, incorporation of various functionalities onto the framework backbone, and as a consequence, fine‐tuning of metal–organic framework (MOF) and covalent organic framework (COF) properties beyond that of any other material class. Leveraging the unique properties of reticular materials has resulted in significant advances from both a fundamental and an applied perspective. Here, we wish to review the milestones in MOF and COF research and give a critical view on progress in their real‐world applications. Finally, we briefly discuss the major challenges in the field that need to be addressed to pave the way for industrial applications.

Selective functionalization of the external surface of porous nanoparticles is of great interest for numerous potential applications in the field of nanotechnology. Regarding metal–organic frameworks (MOFs), few methods for such modifications have been reported in the literature. Herein, we focus on the covalent attachment of functional polymers on the external surface of MIL-100­(Fe) nanoparticles in order to implement properties such as increased chemical and colloidal stability or dye-labeling for the investigation of the particles by fluorescence based techniques. We prove covalent nanoparticles-polymer bond formation by liquid NMR after dissolution of the functionalized MOF under mild conditions and estimate the amount of covalently attached polymer by UV–vis spectroscopy. The functionalization of the MOF nanoparticles with fluorescently labeled polymers enables the investigation of nanoparticle uptake into tumor cells by fluorescence microscopy. Furthermore, the influence of the polymer shell on the magnetic resonance imaging activity of MIL-100­(Fe) is investigated in detail. The functionalization approach presented here is expected to enable the fabrication of hybrid nanomaterials, extending the enormous chemical space of MOFs into polymer materials.

Green chemistry, in particular, the principle of atom economy, has defined new criteria for the efficient and sustainable production of synthetic compounds. In complex nanomaterials, the number of embedded functional entities and the energy expenditure of the assembly process represent additional compound-associated parameters that can be evaluated from an economic viewpoint. In this Perspective, we extend the principle of atom economy to the study and characterization of multifunctionality in nanocarriers, which we define as "multifunctional efficiency". This concept focuses on the design of highly active nanomaterials by maximizing integrated functional building units while minimizing inactive components. Furthermore, synthetic strategies aim to minimize the number of steps and unique reagents required to make multifunctional nanocarriers. The ultimate goal is to synthesize a nanocarrier that is highly specialized but practical and simple to make. Owing to straightforward crystal engineering, metal-organic framework (MOF) nanoparticles are an excellent example to illustrate the idea behind this concept and have the potential to emerge as next-generation drug delivery systems. Here, we highlight examples showing how the combination of the properties of MOFs ( e.g., their organic-inorganic hybrid nature, high surface area, and biodegradability) and induced systematic modifications and functionalizations of the MOF's scaffold itself lead to a nanocarrier with high multifunctional efficiency.