Creatinine-based Cu(II) pincer complex immobilized on UiO-66-NH 2 as an efficient catalyst for the synthesis of 1,4-dihydropyridine and 3,4- dihydropyrimidinone derivatives

An advantageous aspect of anchoring functional groups onto metal-organic frameworks is to provide available active sites within the framework structure, thereby enhancing their catalytic efficiency. The presented study synthesized the pincer ligand using cheap and readily available materials cyanuric chloride and creatinine as the core and side arms, respectively and subsequently reacted with Cu(OAc) ₂ to yield the copper(II) complex. Finally, the UiO-66-NH ₂ framework is modified by the synthesized Cu(II) complex via a covalent post-synthetic modification approach. The functionalized MOF was characterized by different techniques such as FTIR, FE-SEM, EDX, XRD, TGA, and N ₂ adsorption-desorption. The modified MOF, taking advantage of the synergistic effect between copper and zirconium, produces 1,4-dihydropyridine and 3,4-dihydropyrimidinone derivatives. Comparing the prepared nanocatalyst with copper(II) complex and pristine UiO-66-NH ₂ showed that the enhanced catalytic activity of UiO-66-NH ₂ -CC@Cu(II) mainly stems from the presence of the copper(II) complex. This nanocatalyst exhibits high stability and can be recycled for several consecutive cycles without significantly reducing its performance, which is one of the essential parameters for catalyst design in industry.