The
successful discovery of novel multifunctional metal phosphonate
framework materials that incorporate newer organoamines and their
utilization as a potential electroactive material for energy storage
applications (supercapacitors) and as efficient heterogeneous catalysts
are the most enduring challenges at present. From this perspective,
herein, four new inorganic–organic hybrid zinc organodiphosphonate
materials, namely, [C5H14N2]2[Zn6(hedp)4] (I), [C5H14N2]0.5[Zn3(Hhedp)
(hedp)]·2H2O (II), [C6H16N2][Zn3(hedp)2] (III), and [C10H24N4][Zn6(Hhedp)2(hedp)2] (IV) (H4hedp = 1-hydroxyethane 1,1-diphosphonic acid), have been synthesized
through the introduction of different organoamines and then structurally
analyzed using various techniques. The compounds (I–IV) possess a three-dimensional network through alternate
connectivity of zinc ions and diphosphonate ligands, as confirmed
using single-crystal X-ray diffraction. The investigations of electrochemical
charge storage behaviors of the present compounds indicate that compound III exhibits a high specific capacitance of 190 F g–1 (76 C g–1) at 1 A g–1, while
compound II shows an excellent cycling stability of 90.11%
even after 5000 cycles at 5 A g–1 in the 6 M KOH
solution. Further, the present materials have also been utilized as
active heterogeneous Lewis acid catalysts in the ketalization reaction.
The screening of various substrate scopes during the catalytic process
confirms the size-selective heterogeneous catalytic nature of the
framework compounds. To our utmost knowledge, such a size-selective
heterogeneous Lewis acid catalytic behavior has been observed for
the first time in the amine templated inorganic–organic hybrid
framework family. Moreover, the excellent size-selective catalytic
efficiencies with the d10 metal system and recyclability
performances make the compounds (I–IV) more efficient and promising Lewis acid heterogeneous catalysts.