Lanthanum(III) triflate supported on nanomagnetic γ-Fe2O3 was synthesized and characterized by HRTEM, XRD, ICP, FT-IR, TGA and VSM. It was applied as a magnetically recyclable heterogeneous Lewis acid catalyst for the efficient one-pot synthesis of β-phosphonomalonates via tandem Knoevenagel–phospha-Michael reaction. The catalyst was easily separated from the reaction mixture by magnetic decantation using an external magnet and reused ten times.
