SummaryActive and highly stable electrocatalysts for oxygen evolution reaction (OER) in acidic media are currently in high demand as a cleaner alternative to the combustion of fossil fuels. Herein, we report a Co-doped nanorod-like RuO2 electrocatalyst with an abundance of oxygen vacancies achieved through the facile, one-step annealing of a Ru-exchanged ZIF-67 derivative. The compound exhibits ultra-high OER performance in acidic media, with a low overpotential of 169 mV at 10 mA cm−2 while maintaining excellent activity, even when exposed to a 50-h galvanostatic stability test at a constant current of 10 mA cm−2. The dramatic enhancement in OER performance is mainly attributed to the abundance of oxygen vacancies and modulated electronic structure of the Co-doped RuO2 that rely on a vacancy-related lattice oxygen oxidation mechanism (LOM) rather than adsorbate evolution reaction mechanism (AEM), as revealed and supported by experimental characterizations as well as density functional theory (DFT) calculations.

Pt SAC, [3] Au SAC, [4] and Co SAC, [5] have been reported. A few strategies have thus been proposed to fabricate metal SACs, including wet impregnation, [6] metal (hydr) oxides@polymer core−shell strategy, [7] atomic layer deposition, [8] and photochemical strategy. [6] However, the construction of metal SACs remains challenging because of the high surface energy of single atoms. Thus, to further promote the wide application of metal SACs, it is urgent to develop new, advanced, and universal synthetic methodology.Metal-organic frameworks (MOFs), are a unique type of porous materials with ultrahigh porosity, tunable pore sizes, and wellcharacterized crystalline architectures. [9] MOFs are composed of metal ions and organic linkers, serving as excellent templates for the preparation of composite materials with functional species, such as nitrogen-doped carbon and transition metal carbides/nitrides. [10] Recently, MOFs have been employed as templates to fabricate SACs, through adding metal precursors into the synthetic solution of MOFs. It was proposed that the metal precursors were trapped in the cage of the resultant MOF, anchored to the functional group, or incorporated as In the present study, a highly efficient strategy is reported using open framework platforms with abundant chelating ligands to fabricate a series of stable metal single-atom catalysts (SACs). Here, the metal ions are initially anchored onto the active bipyridine sites through postsynthetic modification, followed by pyrolysis and acid leaching. The resulting single metal atoms are uniformly distributed on a nitrogen-doped carbon (N-C) matrix. Interestingly, each metal atom is found to be coordinated with five N atoms, in contrast to the average coordination number of four as previously reported. The as-prepared Fe SAC/N-C catalyst exhibits excellent oxygen reduction reaction (ORR) activity (with a half-wave potential of 0.89 V), outstanding stability, and good methanol tolerance. The density functional calculations reveal that the coordinated pyridine can favorably modulate the interaction strength of oxygen on the Fe ion and thus improve the ORR activity. More importantly, it is demonstrated that this strategy can be successfully extended to the preparation of other transition metal SACs, simply by altering the metal precursors used in the metalation step. Single-Atom CatalystsMetal single-atom catalysts (SACs) with atomically distributed active metal centers have emerged as a new research frontier in the catalytic community because of their maximum atom efficiency and high selectivity in a wide variety of catalytic reactions. [1] To date, quite a few metal SACs, such as Fe SAC, [2] The ORCID identification number(s) for the author(s) of this article can be found under https://doi.

The defect concentration in the prototypical metal–organic framework UiO-66 can be well controlled during synthesis, leading to precisely tunable physicochemical properties for this structure. However, there has been a long-standing debate regarding the nature of the compensating species present at the defective sites. Here, we present unambiguous spectroscopic evidence that the missing-linker defect sites in an ambient environment are compensated with both carboxylate and water (bound through intermolecular hydrogen bonding), which is further supported by ab initio calculations. In contrast to the prevailing assumption that the monocarboxylate groups (COO–) of the modulators form bidentate bonding with two Zr4+ sites, COO– is found to coordinate to an open Zr4+ site in an unidentate mode. The neighboring Zr4+ site is terminated by a coordinating H2O molecule, which helps to stabilize the COO– group. This finding not only provides a new understanding of defect termination in UiO-66, but also sheds light on the origin of its catalytic activity.

Clean separation of linear, monobranched, and dibranched alkanes is achieved using a flexible, microporous metal–organic framework (MOF).