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Abstract Nanoparticles of metal‐organic frameworks (nanoMOFs) possess the unusual combination of both internal and external surfaces. While internal surfaces have been the focus of fundamental and applications‐based MOF studies, the chemistry of the external surfaces remains scarcely understood. Herein we report that specific ion interactions with nanoparticles of Cu(1,2,3‐triazolate)₂(Cu(TA)₂) resemble the Hofmeister behavior of proteins and the supramolecular chemistry of synthetic macromolecules. Inspired by these anion‐selective interactions, we tested the performance of Cu(TA)₂nanoparticles as chemical field effect transistor (ChemFET) anion sensors. Rather than size‐based selectivity, the detection limits of the devices exhibit a Hofmeister trend, with the greatest sensitivity towards anions perchlorate, iodide, and nitrate. These results highlight the importance of the pore‐based supramolecular interactions, rather than localized donor‐acceptor pairs, in designing MOF‐based technologies. 

Native ion mobility-mass spectrometry (IM-MS) typically introduces protein ions into the gas phase through nano-elecrospray ionization (nESI). Many nESI setups have mobile stages for tuning the ion signal and extent of co-solute and salt adduction. However, tuning the position of the emitter capillary in nESI can have unintended downstream consequences for collision-induced unfolding or collision-induced dissociation (CIU/D) experiments. Here we show that relatively small variations in the nESI emitter position can shift the midpoint potential of CID breakdown curves and CIU transitions; by as much as 8 V on commercial instruments.