<p>This work uncovers an insufficiently addressed relationship between hydrothermal synthesis parameters and the resulting physico-chemical properties, surface acidity and catalytic performance of Zn–Fe based nanocatalysts in the production of 3,4-dihydropyrimidinone (DHPM) via the Biginelli reaction under solvent-free conditions, using benzaldehyde, ethyl acetoacetate and urea as reactants. A series of Zn-Fe mixed oxide (Zn/Fe = 1:2) nanomaterials was prepared via the hydrothermal method under various synthesis conditions involving different temperatures and durations (T = 150 and 180&#xa0;°C; t = 24 and 48&#xa0;h). The physicochemical properties and catalytic activity were found to be strongly influenced by the synthesis temperature, while the effect of synthesis duration was less pronounced. Textural characterization revealed mesoporous structures and high specific surface areas. Structural and spectroscopic analyses indicated the formation of a predominant ZnFe₂O₄ phase, accompanied by traces of α-Fe₂O₃. Morphological analysis confirmed the nanoscale size of the Zn-Fe particles. The magnetic properties of the Zn-Fe samples were found to be independent of the hydrothermal synthesis conditions. The samples hydrothermally prepared at 180&#xa0;°C exhibited the highest DHPM yields (exceeding 80% at 100&#xa0;°C after 120&#xa0;min), which is attributed to their higher surface acidity. Reusability tests conducted on the most active catalyst demonstrated its stability, with no significant loss in catalytic performance even after three successive reaction cycles.</p> Graphical Abstract <p></p>