Cd-Based Crystalline Network Material: Catalytic Properties and Post Synthetic Metal-Ion Metathesis with Enhanced Stability and Gas Sorption Behaviour

Abstract

This study presents the synthesis of a Cd(II) based hydrophobic three dimensional crystalline network material (CNM), [Cd3(L)2(LH)2(bpe)2], {L= {4,4'-(hexafluroisopropylidine)bis(benzoate)} and 1,2-di(4-pyridyl) ethylene (bpe)}, 1(Cd), by employing the slow-diffusion method. The three-dimensional structure of 1(Cd) was determined by single crystal X-ray diffraction and characterized by powder X-ray diffraction (PXRD), FT-IR spectroscopy and thermogravimetric analysis (TGA). Subsequent, post-synthetic modification of 1(Cd) with Cu(II) at room temperature led to the formation of isostructural 1(Cu) with partial substitution. This transformation, unattainable through de-novo synthesis, was monitored using energy dispersive X-ray analysis (EDX), PXRD, FT-IR spectroscopy, and through visual observation confirming a single crystal to single crystal metal exchange. The modified material, 1(Cu), exhibited red-shifted emission with enhanced thermal stability and tenfold increase in N2 uptake. Furthermore, the catalytic potential of 1(Cd) in aza-Michael addition reactions of α, β-unsaturated olefins to nucleophilic aromatic/aliphatic amines was demonstrated successfully under ambient conditions. This approach employed a heterogeneous and acid-base free methodology showcasing the versatility and effectiveness of 1(Cd) as a catalyst.