<div><p>The control of the size and morphology of Metal-Organic Frameworks is a challenge that must be overcome to ensure the use of these materials in advanced applications. Mixed Lanthanide-Organic Frameworks (MLOFs) were synthesized via solvo(hydro)thermal method and then characterized by PXRD, IR, TG/DTA, SEM and PL spectroscopy. The effect of the modulator (acetic acid) on the morphological characteristics of the obtained powders was investigated. Trivalent terbium ions were successfully incorporated into La-framework conferring green luminescence to the prepared samples. It was observed that a gradual increase in acetic acid concentration led to the morphology change from micro-rods to flower-like small particle agglomerates. Moreover, a higher concentration of the acetic acid prevented the crystallization of secondary phases.</p></div