Hydrophilic porous polyethersulfone (PES) membranes and microcapsules were prepared via Non-Solvent Induced Phase Separation (NIPS) with the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) as structure control agent, added to the conventionally employed PVPK17 pore former. The introduction of [BMIM][PF6] affects the phase inversion mechanism, resulting in different morphologies of the materials. Optimal conditions for the preparation of membranes (ILMs) were: 10–15 wt.% PES, 0–4 wt.% PVPK17, 5–25 wt.% [BMIM][PF6], while slightly different conditions were applied for the preparation of microcapsules (ILMCs): 10% wt.% PES, 0–4% wt.% PVPK17, and 5–15 wt.% [BMIM][PF6]. Thus, the produced porous spongy microcapsules (average diameter ∼800 μm) and flat sheet ionic liquid membranes (ILMs) were characterized by electronic microscopy (SEM), FTIR and Raman spectroscopy and thermal analysis. [BMIM][PF6] concentration is a key factor for controlling the internal membrane morphology. Indeed, higher concentrations of [BMIM][PF6] additive increases the viscosity of casting solution and reduces solvent exchange speed, thereby altering the membrane morphology from a channelled structures (finger-like) to a spongy type.