## 2 Experimental Section
Figure 6: HRXRD pattern of HAP-Pd catalysts. hydrogenation of nitro compounds in water. Based on the obtained results (Table 1), the reduction of nitroarenes possessing electron donating or withdrawing functions was fulfilled successfully in high yields. Although predicting the exact mechanism of the reactions is rather challenging, we propose the following mechanistic pathway for the formation of aminoaromatics from nitroarenes in this work (Scheme 1). As shown in Scheme 1, the reduction of nitroarenes was carried out using NaBH4 as the reducing agent, which entails two stages in the hydrogenation of nitroarenes to aminoaromatics: (i) Absorption of nitroarene and hydrogen to the metal surfaces, and (ii) electron transfer assisted by metal surfaces from BH4- to nitroarene and then desorption of the amino compound. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & & \\ \hline
**Entry** & **Substrate** & **Product** & **Yield (\%) b** \\ \hline
**1** & & & \\
**2** & & & \\
**3** & & & \\
**4** & & & \\
**5** & & & \\
**6** & & & \\
**7** & & & \\ \hline \hline \end{tabular}  
* Substituted nitroaramatics (1 mmol), NaBH4 (1.2 equiv.), HAP-Pd catalyst (1 mol%), H2O (30 mL), r.t., 2 h. b The yields were determined by GC-MS. c 2.5 equiv. NaBH4 was used.  
\end{table} 
Table 1: Heterogeneous reduction of substituted nitroaroomatics catalyzed by the HAP-Pd catalyst a. Then, we compared the synthesis procedure and the catalytic activity of the HAP-Pd catalyst with the previously published catalysts in the reduction of nitrobenzene (Table S1). A facile synthetic method introduced in this study provided competitive catalytic conversion in mild reaction conditions, as compared to the complicated prepared catalysts [42; 43]. To verify the advantages of the heterogeneous catalytic system, we carried out the reduction of nitrobenzene under homogeneous catalytic conditions using the water-soluble K\({}_{2}\)PdCl\({}_{4}\) catalyst, which did not show reasonable catalytic activity under the reduction conditions (entry 1, Table S1). When NaBH\({}_{4}\) was added to the reaction mixture, K\({}_{2}\)PdCl\({}_{4}\) immediately aggregated forming large-sized particles. The reduction in the absence of the catalyst using NaBH\({}_{4}\) also did not yield the expected product (entry 2, Table S1). Consequently, the friendly reaction medium containing HAP-Pd is an efficient catalytic tool for several important industrial organic transformations with numerous advantages such as benign catalytic system, high yield of products, and the deployment of nontoxic solvent. In addition, the utilization of water soluble reductant and oxidant (e.g., NaBH\({}_{4}\) and H\({}_{2}\)O\({}_{2}\)) in the absence of gas pressure provides less expensive, safer, and more environmentally-benign protocols. Although dehydrogenation of primary and secondary alcohols using solid-supported Pd NPs, including HAP, has been profoundly investigated, they are generally attained under oxygen pressure using hazardous and toxic organic solvents [44]. Therefore, developing mild oxidation processes using H\({}_{2}\)O\({}_{2}\) in a greener oxidant is decidedly important for heterogeneous Pd catalysts [45]. To expand the greener potential application of the synthesized HAP-Pd catalyst, we examined the oxidation of primary and secondary alcohols in water using H\({}_{2}\)O\({}_{2}\) as an oxidant; Table 2 summarizes the results of the dehydrogenative oxidation of benzyl alcohols catalyzed by HAP-Pd. Several primary and secondary alcohols were oxidized affording the desired products in good to excellent yields in water. It should be noted that the alcohol oxidation could not be achieved when we examined the oxidation of cycloheptanol under the identical reaction conditions but in the absence of the HAP-Pd catalyst; this catalytic system shows a marked ability to operate for a wide range of substrates under such optimized conditions.