Layered potassium tetratitanate is synthesized via a solid-state synthesis of TiO2 and K2CO3 at 800 °C, yielding monoclinic K2Ti4O9 (KTO) with a rod-like morphology (Fig. ). The confined interlayer potassium is subsequently exchanged by protons and water via treatment in HCl according to earlier work of Izawa et al. . The resulting hydrogen tetratitanate H2Ti4O9 . H2O (HTO) retains the rod-like morphology of KTO as indicated by scanning electron microscopy (SEM, Fig. ). The rods measure up to several microns in lengths and several hundreds of nanometers in diameter, in agreement with previous reports. The chemical composition of the nanoconfined interlayer environment of HTO can be further modified with organic aminebased molecular pillars replacing interlayer water without leading to any visible modification of the macroscopic rod-like morphology as shown by SEM micrographs (Fig. ). Propylamine (PA) and 1,6-hexanediamine (HDA) are selected as molecular pillars with one or two anchoring amine groups, respectively. The reason is the assumption that monofunctional PA bonds to one layer of the titanate host resulting in a separated HTO structure, while bifunctional HDA interacts with two adjacent titanate layers leading to a cross-linked HTO structure. Hence the pillar choice allows to compare the influence of interconnectivity of the pillared structure on the volumetric expansion behavior when used as electrochemical ion intercalation hosts.