Amine-rich Nickel(II)-Xerogel as a Highly Active Bifunctional Metallo-organo Catalyst for Aqueous Knoevenagel Condensation and Solvent-free CO2 Cycloaddition

Ekata Saha; Hiren Jungi; Shilpa Dabas; Abra Mathew; Rositha Kuniyil; Saravanan Subramanian; Joyee Mitra

doi:10.1021/acs.inorgchem.3c01669

Amine-rich Nickel(II)-Xerogel as a Highly Active Bifunctional Metallo-organo Catalyst for Aqueous Knoevenagel Condensation and Solvent-free CO₂ Cycloaddition

Inorg Chem. 2023 Sep 18;62(37):14959-14970. doi: 10.1021/acs.inorgchem.3c01669. Epub 2023 Sep 6.

Authors

Ekata Saha^{1

2}, Hiren Jungi^{1

2}, Shilpa Dabas^{1

2}, Abra Mathew³, Rositha Kuniyil³, Saravanan Subramanian^{1

2}, Joyee Mitra^{1

2}

Affiliations

¹ Inorganic Materials & Catalysis (IMC) Division, CSIR-Central Salt & Marine Chemicals Research Institute, Gijubhai Badheka Marg, Bhavnagar 364002, Gujarat, India.
² Academy of Scientific and Innovative Research (AcSIR), AcSIR Headquarters, CSIR-HRDC Campus, Sector-19, Kamla Nehru Nagar, Ghaziabad 201002, India.
³ Department of Chemistry, Indian Institute of Technology Palakkad (IIT Palakkad), Palakkad 678623, Kerala, India.

PMID: 37672483
DOI: 10.1021/acs.inorgchem.3c01669

Abstract

Metallogels formed from supramolecular interactions of low-molecular-weight gelators (LMWGs) combine the qualities of heterogeneous catalysts and offer the advantages of multifunctionality owing to the facile installation of desired task-specific moieties on the surface and along the channels of the gels. We discuss the applications of a triazole-based Ni(II) gel-derived xerogel (NiXero) having a high density of Ni(II)-nodes and appended primary amines as a recyclable heterogeneous catalyst for Knoevenagel condensation of aldehyde and malononitrile in water and the solvent-free cycloaddition of CO₂ to form a series of cyclic carbonates with near-quantitative conversion of the respective epoxides, with low catalyst loading (0.59 mol %), high catalyst stability, and recyclability. The structural advantages of NiXero, due to the concurrent presence of bifunctional Lewis acid-base sites on the channels, open Ni(II) nodes, N_triazole, pendant -NH₂ and its chemical stability, are conducive to the cooperative heterogeneous catalytic activity under mild conditions. This work emphasizes the effective amalgamation of metals with purpose-built ligand systems for the construction of metallogels and their utility as heterogeneous catalysts for desired organic transformations.