This study employs NMR for the first time to study the nature of the interaction between organic electrolytes and a conductive layered MOF, and how these interactions impact the charging mechanism. Solid-state NMR reveals separate in-pore and ex-pore electrolyte environments in Ni3(HITP)2, enabling the study of the electrochemical double layer separately from bulk electrolyte. Our experimental spectra alongside the QM/MM and density functional theory (DFT) calculations reveal that specific interactions between the MOF and the electrolyte dominate the observed chemical shifts and we further find a correlation between measured in-pore ion populations and supercapacitor performance in different MOF batches. Finally, ex-situ NMR and operando EQCM experiments reveal the cation-dominated charging mechanism of the conductive MOF supercapacitor device. We suggest that exploring the interplay between MOF-electrolyte interactions, charging mechanisms, and performance could lead to the design of improved supercapacitor systems.