Single-atom catalysts (SACs) show expressively enhanced activity toward diverse reactions due to maximized atomic utilization of metal sites, while their facile, universal, and massive preparation remains a pronounced challenge. Here we report a facile strategy for the preparation of SACs by use of the inherent confined space between the template and silica walls in template-occupied mesoporous silica SBA-15 (TOS). Different transition metal precursors can be introduced into the confined space readily by grinding, and during succeeding calcination single atoms are constructed in the form of M−O− Si (M = Cu, Co, Ni, and Zn). In addition to the generality, the present strategy is easy to scale up and can allow the synthesis of 10 g of SACs in one pot through ball milling. The Cu SAC has been applied for CO 2 cycloaddition of epichlorohydrin, and the activity is obviously higher than the counterpart prepared without confined space and various reported Cu-containing catalysts.
Solid superbases can catalyze diverse reactions under mild conditions, while they suffer from aggregation of basic sites and poor stability during recycling.Here we report a new generation of solid superbases derived from K single atoms (SAs) prepared by a tandem redox strategy. The initial redox reaction takes place between base precursor KNO 3 and graphene support, producing K 2 O at 400 °C. Further increasing the temperature to 800 °C, the graphene reduces K 2 O to K anchored by its vacancies, leading to the generation of K SAs (denoted as K 1 /G). The source of basicity in the K 1 / G is K SAs, and neighboring single atoms (NSAs) possess superbasicity, which is different from conventional basicity originated from oxygen and nitrogen atoms. Due to the superbasicity as well as high dispersion and anchoring of basic sites, the K 1 /G shows excellent catalytic activity and stability in transesterification reaction, which is much superior to the reported catalysts.
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