A Cellulose-Based Aerogel Prepared via a Zero-Waste Route as a Recyclable Heterogeneous Base Catalyst for Organic Transformation Reactions

The exploitation of green and renewable resources for the development of sustainable catalysts is an ideal concept toward eco-friendly chemical transformations. In this regard, we have designed and synthesized a 3D sodium carboxymethyl cellulose-based biopolymer aerogel (CGH) under a catalyst-free condition in an aqueous medium using hydroxyethyl cellulose (HEC) as the structural reinforcing agent and ethylene glycol tetraacetic acid (EGTA) as the cross-linker. The synthesized aerogel exhibits a porous, mechanically robust, and thermally stable architecture, characterized using various state-of-the-art physicochemical techniques including FT-IR, 13 C CPMAS, PXRD, TGA, DSC, BET, SEM, and XPS analyses. Owing to the presence of basic sites, CGH was utilized as a heterogeneous catalyst in the Knoevenagel condensation reaction and Biginelli reaction under mild and eco-friendly conditions to produce desired compounds in high yields at room temperature. Furthermore, the catalyst preparation and the catalyst’s use in these transformations resulted in minimal waste generation, achieving an excellent E-factor of 0 for the synthesis of CGH with the process mass intensity value of 1.10 for the gram-scale Biginelli reaction, thereby demonstrating catalyst’s remarkable environmental friendliness and efficiency. Additionally, CGH exhibited excellent recoverability and recyclability without any appreciable decrease in its catalytic activity for at least eight cycles. This study establishes CGH as a biodegradable, zero-waste cellulose-based aerogel as a sustainable heterogeneous catalyst, opening new paradigms for the development of environmentally friendly catalytic approaches.