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Open metal sites (OMSs) represent a distinctive feature of metal-organic frameworks (MOFs), intertwined with guest accommodation and energy transfer within nanosized pores. Fine-tuning OMSs provide an effective approach to regulating MOF’s responsiveness and binding affinity towards guests, allowing for the construction of luminescent sensors for specific analytes. Such a strategy remains unexplored due to the inherent complexity of the systems and sensing mechanisms. Herein, we delicately regulated the OMSs in PCN-700 through multiple synthetic methodologies, including direct synthesis, linker installation, and linker exchange. The resultant MOFs consist of Zr6-clusters featuring various coordination numbers. Notably, PCN-700-8u with unsaturated 8-coordinated Zr-clusters exhibited the highest sensitivity in detecting a toxic pesticide pentachloronitrobenzene (PCNB) due to the presence of strong coordination interaction, as validated through single crystal X-ray diffraction directly. PCN-700-10u/12u bearing unsaturated 10/12-coordinated clusters perform lower quenching efficiencies than PCN-700-8u, but higher than PCN-700-12s with saturated clusters. In contrast, all these MOFs exhibit similar quenching efficiencies towards hexachlorobenzene for the absence of coordination interaction. This study not only develops a cost-effective and easily attainable material for PCNB detection, but also illuminates the pivotal importance of OMSs in customizing MOF-based sensors for practical applications.

Particle exchange heat engines are a novel class of cyclic heat engines that are all-electrical, contain no moving parts and can therefore be scaled down to nanometer size. At the center of their operation is the manipulation of a particle flow between a hot and a cold reservoir through energy filtering mechanisms, where their efficiency depends primarily on the sharpness of the energy filter. In this study, we investigate the efficiency enhancement of such engines by utilizing ultra-sharp transmission resonances formed by magnetic impurities interacting with superconductors, known as Yu-Shiba-Rusinov bound states. To this end, we couple a neutral and stable diradical molecule to superconducting break-junction electrodes, and study its thermoelectric properties at ultra-low temperatures. By driving the molecular heat engine through a phase transition from a Kondo state into the Yu-Shiba-Rusinov regime, we observe a five fold increase in the thermoelectric power factor. This observation could pave the way for practical applications such as cryogenic waste heat recovery and efficient spot-cooling for future quantum computing architectures.

Trifluoromethylation is a key transformation in drug and agrochemical synthesis, yet current reagents often suffer from high cost, low atom economy, and low scalability. [Discover more...]

Iron photosensitizers represent a holy grail in photochemistry, but their widespread implementation is limited by their short excited-state lifetimes and poor cage escape yields.

The swelling of a polymer matrix by ionic liquids and additional lithium salts may lead to the formation of ionogel electrolytes. However, the introduction of additional ions usually results in a decreased lithium-ion transference number, because of the trapping of the lithium ions in clusters and polymer-ion complexes. [Discover more...]