Synergistic Lewis acid-base sites of ultrathin porous Co3O4 nanosheets with enhanced peroxidase-like activity

Abstract

Surface Lewis acid-base sites in crystal structure may influence the physicochemical properties and the catalytic performances in nanozymes. Understanding the synergistic effect mechanism of Co 3 O 4 nanozymes towards substances (3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H 2 O 2 )) induced by surface Lewis acid-base sites is important to enhance the efficiency for peroxidase-like reaction. Herein, ultrathin porous Co 3 O 4 nanosheets with abundant Lewis acid-base sites were prepared by sodium borohydride (NaBH 4 ) reduction treatment, which exhibited high-efficiency peroxidase-like activity compared with original Co 3 O 4 nanosheets. The Lewis acid-base sites for ultrathin porous Co 3 O 4 nanosheets nanozyme were owing to the coordination unsaturation of Co ions and the formation of defect structure. Ultrathin porous Co 3 O 4 nanosheets had 18.26-fold higher catalytic efficiency (1.27 × 10 −2 s −1 •mM −1 ) than that of original Co 3 O 4 (6.95 × 10 −4 s −1 •mM −1 ) in oxidizing TMB substrate. The synergistic effect of surface acid and base sites can enhance the interfacial electron transfer process of Co 3 O 4 nanosheets, which can be a favor of absorption substrates and the generation of reactive intermediates such as radicals. Furthermore, the limit of detection of hydroquinol was 0.58 μM for ultrathin porous Co 3 O 4 nanosheets, 965-fold lower than original Co 3 O 4 (560 μM). Besides, the linear range of ultrathin porous Co 3 O 4 nanosheets was widely with the concentration of 5.0-1,000 μM. Colorimetric detection of hydroquinol by agarose-based hydrogel membrane was provided based on excellent peroxidase-like properties. This study provided insights into designing high-performance nanozymes for peroxidase-like catalysis via a strategy of solid surface acid-base sites engineering.

Bimetallic Metal–Organic Frameworks MIL-53(xAl–yFe) as Efficient Catalysts for H2S Selective Oxidation

“… , Notably, the NMR spectrum of MIL-53­(1Al–5Fe) has a slight blue shift, suggesting the generation of unsaturated coordination sites (CUS). It should be noted that the CUS and structural defect sites in MOFs can be used as LAS to increase the absorption of the reactants, thereby facilitating the transfer of electrons and the generation of reactive intermediates. − Importantly, such bimetallic MIL-53­( x Al– y Fe) catalysts with surface-isolated CUS active sites can enhance the absorption and activation of H 2 S, which can accelerate the dissociation and oxidation of H 2 S to HS* or S*, thus increasing the oxidative desulfurization efficiency. In this regard, bimetallic MIL-53­( x Al– y Fe) catalysts with an increased number of LAS on the surface can achieve the effective catalytic elimination of H 2 S.…”

Insights on catalytic mechanism of CeO2 as multiple nanozymes

“…The concept of nanozymes is an interdisciplinary field, which bridges the disciplines of enzymology and heterogeneous catalysis. To date, the catalytic performance of nanozymes is generally analyzed by the Michaelis-Menten equation, in which two parameters of k cat and K m are used to describe the catalytic reaction rate and adsorption affinity of substrates on the surfaces of nanozymes, respectively [7,[26][27][28][29][30]. This method is practically adopted to understand the catalytic kinetics of natural enzymes, which cannot accurately reflect the catalytic mechanism of nanozymes.…”

Confinement chemistry of FeOx centers for activating molecular oxygen under ambient conditions

“…We propose that pore-confined FeO x centers in porous Pt/ CeO 2 nanospheres could be prototype catalysts with general impacts on effective activation of O 2 , which is based on the following considerations pertinent to the confinement chemistry: (i) key roles of the compositions. FeO x has a relatively strong redox ability that allows the creation of active oxygen species for catalytic uses, [2][3][4][5] while CeO 2 is a known support with excellent oxygen mobile and oxidation abilities. Pt usually acts as an active site, [6][7][8] over which there exists competitive adsorption of CO and O 2 .…”