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Herein, we report a novel carbothermal welding strategy to prepare atomically dispersed Pd sites anchored on a three-dimensional (3D) ZrO2 nanonet (Pd1@ZrO2) via two-step pyrolysis, which were evolved from isolated Pd sites anchored on linker-derived nitrogen-doped carbon (Pd1@NC/ZrO2). First, the NH2–H2BDC linkers and Zr6-based [Zr6(μ3-O)4(μ3-OH)4]12+ nodes of UiO-66-NH2 were transformed into amorphous N-doped carbon skeletons (NC) and ZrO2 nanoclusters under an argon atmosphere, respectively. The NC supports can simultaneously reduce and anchor the Pd sites, forming isolated Pd1–N/C sites. Then, switching the argon to air, the carbonaceous skeletons are gasified and the ZrO2 nanoclusters are welded into a rigid and porous nanonet. Moreover, the reductive carbon will result in abundant oxygen (O*) defects, which could help to capture the migratory Pd1 species, leaving a sintering-resistant Pd1@ZrO2 catalyst via atom trapping. This Pd1@ZrO2 nanonet can act as a semi-homogeneous catalyst to boost the direct synthesis of indole through hydrogenation and intramolecular condensation processes, with an excellent turnover frequency (1109.2 h–1) and 94% selectivity.

Nanomaterials with enzyme‐mimicking characteristics have engaged great awareness in various fields owing to their comparative low cost, high stability, and large‐scale preparation. However, the wide application of nanozymes is seriously restricted by the relatively low catalytic activity and poor specificity, primarily because of the inhomogeneous catalytic sites and unclear catalytic mechanisms. Herein, a support‐sacrificed strategy is demonstrated to prepare a single iron site nanozyme (Fe SSN) dispersed on the porous N‐doped carbon. With well‐defined coordination structure and high density of active sites, the Fe SSN performs prominent peroxidase‐like activity by efficiently activating H2O2 into hydroxyl radical (•OH) species. Furthermore, the Fe SSN is applied in colorimetric detection of glucose through a multienzyme biocatalytic cascade platform. Moreover, a low‐cost integrated agarose‐based hydrogel colorimetric biosensor is designed and successfully achieves the visualization evaluation and quantitative detection of glucose. This work expands the application of single‐site catalysts in the fields of nanozyme‐based biosensors and personal biomedical diagnosis.

Searching for low-cost, environmentally friendly, and highly active catalysts for C−H bond activation in propane dehydrogenation (PDH) reaction remains a great challenge. Herein, SiO 2 nanomeshes (NMs) with ultrashort three-dimensional (3D) channels were constructed to effectively confine the Co single atoms (Co SAs/ SiO 2 NMs). The ultrashort 3D channels were formed by gasifying carbon in the self-assembled SiO 2 @polymer composites under the air atmosphere. The carbon removal process resulted in abundant oxygen (O*) defects in the channel windowsill that immobilized the dissociative Co 1 species to afford the sintering-resistant Co SAs/SiO 2 NMs catalyst. The as-obtained Co SAs/SiO 2 NMs with unsaturated Co−O 3 sites exhibited an outstanding PDH catalytic behavior (95% selectivity and 196 h −1 turnover frequency), superior to Co SAs/SiO 2 commerce (83%, 49 h −1 ), Co NPs/SiO 2 NMs (87%, 13 h −1 ), and most non-noble metal-based catalysts. Furthermore, Co SAs/SiO 2 NMs showed high long-term stability with no significant deactivation during 24 h of reaction. Theoretical and experimental analysis indicated that these unsaturated Co−O 3 sites could selectively activate the first and second C−H bonds and limit the further splitting of C−H (C) bonds during PDH. This work paves a way for designing high-efficiency single-atom catalysts for PDH.

Rationally constructing single-atom enzymes (SAEs) with superior activity, robust stability, and good biocompatibility is crucial for tumor therapy but still remains a substantial challenge. In this work, we adopt biocompatible carbon dots as the carrier material to load Ru single atoms, achieving Ru SAEs with superior multiple enzyme-like activity and stability. Ru SAEs behave as oxidase, peroxidase, and glutathione oxidase mimics to synchronously catalyze the generation of reactive oxygen species (ROS) and the depletion of glutathione, thus amplifying the ROS damage and finally causing the death of cancer cells. Notably, Ru SAEs exhibit excellent peroxidaselike activity with a specific activity of 7.5 U/mg, which surpasses most of the reported SAEs and is 20 times higher than that of Ru/C. Theoretical results reveal that the electrons of the Ru 4d orbital in Ru SAEs are transferred to O atoms in H 2 O 2 and then efficiently activate H 2 O 2 to produce • OH. Our work may provide some inspiration for the design of SAEs for cancer therapy.

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