A magnetically-separable H3PW12O40@Fe3O4/EN-MIL-101 catalyst for the one-pot solventless synthesis of 2H-indazolo[2,1-b] phthalazine-triones

A magnetic inorganic-organic catalyst, PTA@Fe3O4/EN-MIL-101 (EN = ethylenediamine, PTA = phosphotungstic acid) was fabricated and characterized by XRD, HRTEM, FESEM, UV–vis, TGA-DTA, FT-IR, XPS and porosimetry. PTA retained the parent Keggin structure upon dispersion throughout the amine-functionalized chromium terephthalate metal-organic framework, over which magnetic Fe3O4 nanoparticles were previously introduced. The resulting composite heterogeneous solid acid was an active catalyst for the one-pot synthesis of diverse 2H-indazolo[2,1-b] phthalazine-triones in good → excellent yields under mild, solventless condition, and offers facile separation and excellent recyclability.