Unlocking the Potential\nof Acidic–Basic Catalytic\nSites in Nitrogen-Rich Multifunctional Zirconium Phosphate-Based Hybrid\nMaterial for Selective CO<sub>2</sub> Chemical Transformation

Rational\ndesign and development of an acid–base\nmultifunctional\ncatalyst is a difficult task. Here, a multifunctional zirconium phosphate-based\ninorganic–organic hybrid catalyst (ZPCC), incorporating both\nacidic and basic sites, was synthesized by exfoliating α-ZrP\nand subsequently functionalizing it with 3-aminopropyltriethoxysilane\n(APTES) and cyanuric chloride. The as-synthesized catalyst exhibits\noutstanding catalytic performance for the transformation of carbon\ndioxide into cyclic carbonates with high selectivity using a low cocatalyst\ndose under solvent-free conditions. The catalyst ZPCC features Zr<sup>4+</sup> and P–OH groups as acidic sites, and N-containing\nmoieties [secondary amine (−NH−) and triazine ring (−CN−)]\nimpart basic nature to the catalyst. This combination of acid and\nbase sites enacts a synergetic effect on the activation of epoxide\nand CO<sub>2</sub>, respectively, and also increases the cocatalyst\nactivity to open or close the epoxide ring. The functionalized catalyst,\nZPCC, exhibited 50% conversion, 49% yield, and 95% selectivity toward\ncyclic carbonate without any cocatalyst, and it shows almost 100%\nconversion, 99% yield, and 99% selectivity at optimized conditions\n(including a minimal amount of cocatalyst and short reaction period).\nNuclear magnetic resonance and GC–MS techniques were used to\nfind a plausible mechanism and reveal the direct preparation of cyclic\ncarbonates without any byproduct formation. The characterization of\nthe used catalyst, easy recoverability, and the ability to be recycled\nover five times with more than 90% conversion demonstrate its ability\nto be used as a suitable catalyst for industrial purposes.