A Cd-based crystalline network material: catalytic properties and post-synthetic metal-ion metathesis with enhanced stability and gas sorption behaviour.

This study presents the synthesis of a Cd(II) based hydrophobic three dimensional crystalline network material (CNM), [Cd(L)(LH)(bpe)], {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). Subsequently, 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 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 a tenfold increase in N 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.