Nanocasting nanoporous nickel oxides from mesoporous silicas and their comparative catalytic applications for the reduction of p-nitrophenol

• Nanoporous nickel oxides were fabricatied by nanocasting. • MCM-41 and KCC-1 were used as the mesoporous silica templates. • The resulting nanoporous nickel oxides resembled a replica of each template's inner architecture. • Nanoporous nickel oxides are used for the reduction of p- nitrophenol. • NiO-MCM presents higher catalytic properties than NiO-KCC due to a better improved molecular diffusion. Herein, nanoporous nickel oxides were prepared through nanocasting using ordered- and less-ordered mesoporous silica templates, i.e., MCM-41 and KCC-1, respectively. The products resembled the replica of the inner architecture of each template. NiO-MCM-41 (nanocasted in MCM-41) possessed a highly ordered structure originating from the arrangement of nanorods resulting in a large specific surface area of 53 m 2 g −1 . On the other hand, NiO-KCC-1 (nanocasted in KCC-1) exhibited the combination of ordered nanorod and non-ordered foam-like structures with a less specific surface area of 23 m 2 g −1 . Ultimately, the catalytic tests in the reduction of p -nitrophenol ( p -NP) with sodium borohydride (NaBH 4 ) demonstrated that NiO-MCM-41 had significantly higher activity ( k obs = 0.25 min −1 ) and better reusability ( p -NP conversion of 92% after 3 times reactions) than those of NiO-KCC-1 ( k obs = 0.14 min −1 and a 35% p -NP conversion after 3 times reactions) due to the more improved molecular diffusion within a highly ordered structure. The preferred mechanism was found to follow the Langmuir–Hinshelwood route in which both reactants ( p -NP and [BH 4 ] − ) were initially adsorbed onto the surface of the catalyst.