MBC-Guanidine-Ni: A Stable Magnetic Biochar-Based Nanocatalyst for Optimization and Control of A 3 Coupling in the Propargylamine Synthesis

Synthesis of guanidine-functionalized and nickel-functionalized magnetic biochar nanoparticles (MBC-guanidine-Ni) was done through a multi-step protocol, including pyrolysis, precipitation of Fe 3 O 4 , silane grafting, guanidine modification, and coordination of nickel to magnetic biochar nanoparticles using olive kernel waste. The catalyst that was obtained had a nickel content of 4.14 wt% (EDX) and saturation magnetization of 42.01 emu/g, making it possible to separate the catalyst within less than 20 s. Successful functionalization, high dispersion of nickel species, and good thermal stability up to 300 °C were determined by structural characterization (XRD, FT-IR, TEM, BET, XPS, and TGA). A3 model coupling (benzaldehyde, morpholine, phenylacetylene) reaction optimization studies indicated that in solvent-free conditions at 90 °C with 15 mg catalyst, propargylamines were produced in a yield of up to 98% within 30-55 min. The catalyst was reused seven times, successively, with insignificant loss of activity (98% to 94%). Hot filtration and ICP-OES analysis showed very low nickel leaching (<0.5%). The combined activities of guanidine and nickel were necessary to achieve better catalytic activity, as demonstrated by control experiments verifying the dual-activation mechanism of synergy. The decrease in the E-factor relative to the former systems, the solvent-free protocol, and the biomass-based base is a factor in favor of better sustainability metrics and supports the system's environmental friendliness and cost savings.