## 3 Applications of Magnetically Recyclable Nanocatalysis (MRNCs) in Water
The TEM images (10-35 nm) of the fresh catalyst and recovered catalyst after fifth cycle are depicted in Figure 4, indicating no change in the morphology of the \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/HAP nanocatalyst. **Scheme 25. **\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/HAP\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/HAP, was deployed in the synthesis of disubstituted 1,2,3-triazolees from terminal alkynes and _in situ_ generated organic azide in aqueous media; this greener methodology emerges as a new approach for one-pot synthesis of 1,2,3-triazolees in water without the addition of any reagent/base (Scheme 15). The use of an iron-based heterogeneous catalyst instead of the commonly used copper or ruthenium ones renders this methodology comparatively more economical, experimentally simple, and, therefore appealing for industrial use. Fe\({}_{3}\)O\({}_{4}\)-Pd nanocomposite having core-satellite heterostructure, has been used for decarboxylative coupling reactions in aqueous media by [PERSON] and co-workers [57]. The catalyst, Fe\({}_{3}\)O\({}_{4}\)-Pd nanocomposite having core-satellite heterostructure, was prepared by reactions of Pluronic polymer (P123, PEO19-PPO69-PEO19)-coated Fe\({}_{3}\)O\({}_{4}\) nanoparticle and Na\({}_{2}\)PdCl\({}_{4}\) as palladium source (Scheme 16). **Scheme 16. ** Synthesis of Fe\({}_{3}\)O\({}_{4}\)-Pd nanocomposite. Notably, the nanoparticle surface stabilized by Pluronic copolymer would act as nanoreactors to help the solubility of organic reactants and permit the reactants to interact more intimately with the Pd nanoparticles. The activity and selectivity of Fe\({}_{3}\)O\({}_{4}\)-Pd MNPs (Pd nanoparticles having 2:1 \(\pm\) 0:4 nm in average size around Fe\({}_{3}\)O\({}_{4}\) nanoparticle and core-satellites heterostructure) were then investigated for the decarboxylic coupling reaction of allyl alkynoate, in aqueous media (Table 1). \begin{table}
\begin{tabular}{c c c c c} \hline
**Entry** & **Catalyst** & **_T_\({}^{\infty}\)C** & **_t_/**h** & **Isolated Yield (\%)** \\ \hline
1 & 5 mol\% Fe\({}_{3}\)O\({}_{4}\)–Pd & 85 & 2 & 25(3)(70) 1  \\
2 & 5 mol\% Fe\({}_{3}\)O\({}_{4}\)–Pd & 85 & 12 & 95(3) \\
3 & Recovered from entry 2 & 85 & 12 & 88(3) \\
4 & 5 mol\% Pd/C & 85 & 12 & 20(4(2):1(3)) 2  \\
5 & 5 mol\% Pd(PPh)\({}_{4}\) & 85 & 6 & 92(4(2):1(3)) 2  \\ \end{tabular}
\end{table} 
Table 1: Catalytic decarboxylic coupling reaction of allyl alkynoate, in aqueous media. The reaction was performed by addition of a sparingly water-soluble substrate into an aqueous suspension of Pd-Fe\({}_{3}\)O\({}_{4}\), which showed good catalytic activity for 3-phenyl-2-propynoic acid 2-propenyl ester (**3**), providing 95% yield of the decarboxylated product; commercially available Pd on charcoal afforded 20% yield, under the similar reaction condition. The treatment of 1 with Pd(PPh\({}_{3}\))\({}_{4}\) and Pd on charcoal gave a mixture of products 2 and 3 (Table 1). The activity and selectivity of the Pd-Fe\({}_{3}\)O\({}_{4}\) for catalyzing aqueous decarboxylative coupling reactions, avoids the use of hazardous organic solvent and ensure its easy reusability and recovery via magnetic separation. [PERSON] and co-workers have reported the catalytic activity of the FecorePtshell NPs capped with \(\gamma\)-cyclodextrintrin (CD) for hydrogenation reactions in aqueous medium [58]. The magnetically separable catalyst capped with \(\gamma\)-CD was synthesized from iron and Pt precursors to generate FePt NPs with Fe-rich core and Pt-rich shell, which renders them water-dispersible, rather than in organic solvents. The catalytic activity of FecorePtshell NPs capped with \(\gamma\)-CD was investigated for the aqueous hydrogenation reaction of \(p\)-nitrophenol and the corresponding \(p\)-aminophenols were obtained in excellent yield (Scheme 17). **Scheme 17. ** Reduction of p-nitrophenol in aqueous medium.