Nano-crystalline HoCrO4: Efficient catalyst for Knoevenagel condensation in water: First catalytic application of Cr(V) species

A novel nanostructured HoCrO4 material with zircon type structure with Cr(+V) species was prepared by fuel deficient combustion method. The prepared material was well characterized by using XRD, TEM, BET and TPD techniques. Wide range of aromatic aldehydes were effectively coupled with malononitrile in an aqueous media over HoCrO4 in merely 15 to 20 min at room temperature. To the best of our knowledge this is the first catalytic application of HoCrO4 material. [Display omitted] •Synthesis and characterization of novel nanostructured HoCrO4 material.•First catalytic application of HoCrO4 having Cr(V) species in liquid phase catalysis.•Wide range of aromatic aldehydes were effectively coupled with malononitrile over HoCrO4 material in merely 15–20 mins.•Shorter reaction time, less amount of catalyst loading, use of aqueous media and comparable yields of products make protocol greener and interesting.