Efficient heterogeneous catalysis by dual ligand Zn(ii)/Cd(ii) MOFs for the Knoevenagel condensation reaction: adaptable synthetic routes, characterization, crystal structures and luminescence studies

Abstract

Dual ligand MOFs {[Zn(ADA)(L)]·2H₂O}_n (1) and {[Cd(ADA)(L)]·2H₂O}_n (2) involving Zn(II)/Cd(II) metal centres and flexible 1,3-adamantanediacetic acid (H₂ADA)/pyridyl based Schiff base ligand, 4-pyridylcarboxaldehydeisonicotinoylhydrazone (L) as linkers have been efficiently synthesized including green mechanochemical methods and characterised using various analytical methods. Crystal structures of both MOFs, and luminescence and semiconducting properties have also been investigated. Both materials were exploited for efficient catalytic activity in the Knoevenagel condensation reaction for a variety of substrates with good yields and recyclability under ambient reaction conditions in aqueous media. Probably the Lewis acidic metal centre and the presence of amide functionality in the L of the MOFs are cooperatively involved in the efficient condensation reaction by these catalytic materials.