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Regulating the coordination environment of single‐atom sites is of high necessity to promote the catalytic performances of the photocatalysts. Herein, the preparation of atomically dispersed Co‐Ag dual‐metal sites anchored on P‐doped carbon nitride (Co1Ag1‐PCN) via supramolecular and solvothermal approaches is reported, which demonstrates desirable performance for photocatalytic H2 evolution from water splitting. The optimal Co1Ag1‐PCN catalyst achieves a remarkable hydrogen production rate of 1190 µmol g−1 h−1 with an apparent quantum yield (AQY) of 1.49% at 365 nm, superior to most of the newly reported metal‐N‐coordinated photocatalysts. Systematic experimental characterizations and density functional theoretic studies attribute the enhanced photocatalytic activity to the synergistic effect of Co‐Ag dual sites with exclusive coordination configuration of Co‐N6 and Ag‐N2C2, which enhances the charge density and promotes oriented electrons transport to the metal centers with reduced free energy barriers by facilitating the formation of H* intermediates as the key step in hydrogen evolution. This study reveals a versatile strategy to tailor the electronic structures of dual‐metal sites with synergies by engineering the neighboring coordination environment. [ABSTRACT FROM AUTHOR]

Solar‐driven transfer hydrogenation of unsaturated bonds has received considerable attention in the research area of sustainable organic synthesis; however, water, the ultimate green source of hydrogen, has rarely been investigated due to the high barrier associated with splitting of water molecules. We report a carbon‐nitride‐supported palladium single‐atom heterogeneous catalyst with unparalleled performance in photocatalytic water‐donating transfer hydrogenation compared to its nanoparticle counterparts. Isotopic‐labeling experiments and operando nuclear magnetic resonance measurements confirm the direct hydrogenation mechanism using in situ‐generated protons from water splitting under visible‐light irradiation. Density functional theory calculations attribute the high activity to lower barriers for hydrogenation, facilitated desorption of ethylbenzene, and facile hydrogen replenishment from water on the atomic palladium sites. [ABSTRACT FROM AUTHOR]

Abstract: CO2 hydrogenation is attracting increasing attention as a sustainable route to produce formic acid, a commodity and potential energy vector. Here, bifunctional catalysts comprising metal nanoparticles deposited on bulk graphitic carbon nitride were assessed under base‐free conditions, identifying supported Pd as the best performer. The catalyst productivity was enhanced by maximizing the edge‐defects of the g‐C3N4 carrier, amino groups able to activate CO2, and by generating welldispersed 5 nm Pd particles, required to split H2. Bottom‐up synthesis methods, that is, hard‐templating and carbon enrichment upon polymerization, and top‐down strategies, that is, thermal exfoliation of the as‐prepared solid, were explored to boost the defects, the nature and density of which were evaluated by thermal and (in situ) spectroscopic techniques. After optimization of temperature, pressure, and reaction time, a 20 times higher turnover frequency compared with the best Pd/g‐C3N4 catalyst reported producing formic acid from CO2 without base was attained. This activity level was retained upon recycling with intermediate catalyst regeneration at mild temperature. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) exhibits unique properties as a support for single-atom heterogeneous catalysts (SAHCs). Understanding how the synthesis method, carrier properties, and metal identity impact the isolation of metal centers is essential to guide their design. This study compares the effectiveness of direct and postsynthetic routes to prepare SAHCs by incorporating palladium, silver, iridium, platinum, or gold in g-C3N4 of distinct morphology (bulk, mesoporous and exfoliated). The speciation (single atoms, dimers, clusters, or nanoparticles), distribution, and oxidation state of the supported metals are characterized by multiple techniques including extensive use of aberration-corrected electron microscopy. SAHCs are most readily attained via direct approaches applying copolymerizable metal precursors and employing high surface area carriers. In contrast, although post-synthetic routes enable improved control over the metal loading, nanoparticle formation is more prevalent. Comparison of the carrier morphologies also points toward the involvement of defects in stabilizing single atoms. The distinct metal dispersions are rationalized by density functional theory and kinetic Monte Carlo simulations, highlighting the interplay between the adsorption energetics and diffusion kinetics. Evaluation in the continuous three-phase semihydrogenation of 1-hexyne identifies controlling the metal-carrier interaction and exposing the metal sites at the surface layer as key challenges in designing efficient SAHCs. [ABSTRACT FROM AUTHOR]

We report the preparation and hydrogenation performance of a single-site palladium catalyst that was obtained by the anchoring of Pd atoms into the cavities of mesoporous polymeric graphitic carbon nitride. The characterization of the material confirmed the atomic dispersion of the palladium phase throughout the sample. The catalyst was applied for three-phase hydrogenations of alkynes and nitroarenes in a continuous-flow reactor, showing its high activity and product selectivity in comparison with benchmark catalysts based on nanoparticles. Density functional theory calculations provided fundamental insights into the material structure and attributed the high catalyst activity and selectivity to the facile hydrogen activation and hydrocarbon adsorption on atomically dispersed Pd sites. [ABSTRACT FROM AUTHOR]

In article number 1605785, Javier Pérez‐Ramírez and co‐workers investigate the synthesis of single‐atom heterogeneous catalysts based on precious metals and using graphitic carbon nitride as the carrier. Advanced characterization and simulations reveal the impact of the carrier properties, and of the metal identity and method of introduction on the speciation. Controlling the metal‐carrier interaction and exposing the reactive metal centers are key for maximizing the potential of these materials. [ABSTRACT FROM AUTHOR]

Most birds build nests to incubate their eggs and raise their young in a protective environment. In their Communication on page 11265 ff., J. Pérez‐Ramírez, N. López et al. apply a nesting concept to anchor isolated palladium atoms within the cavities of graphitic carbon nitride. This leads to a stable single‐site heterogeneous catalyst with outstanding performance in hydrogenation reactions (artwork concept: Amalia Gallardo, illustration: Marcel Reich). [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbons (NC) and carbon nitride (C 3 N 4) belong to the two fundamental pillars of functionalized carbon materials that have broad applications in different fields. The synthesis of NC and C 3 N 4 often starts from different precursors, and a general approach that can offer both architectures is still highly sought. Herein, a facile Triton X-100-assisted copolymerization-carbonization strategy is reported to fulfill this task. By moderating the weight ratios of Triton X-100 and several conventional precursors of C 3 N 4 (e.g., dicyandiamide, urea, and cyanamide), a series of both types of N-functionalized carbons with controllable N dopants is successfully afforded. The yielded solids transform from graphitic C 3 N 4 with low surface areas to porous NC when the weight ratio reaches the critical values. This phenomenon might be attributed to the intensified copolymerization between the intermediates of both starting precursors during the carbonization, resulting in increased oxygen content and decreased N:C ratio in the products. Both the bulk and activated carbon-supported materials are then designed and used as metal-free catalysts in the dehydrochlorination of ethylene dichloride, a key reaction in polyvinyl chloride manufacture. It is found that NC is significantly more active than C 3 N 4 , but the corresponding supported catalysts exhibit an opposing trend. The structure-activity correlations suggest both the number of different N defects and the surface areas might play key roles in determining the dehydrochlorination chemistry. Tailor synthesis of C 3 N 4 and N-doped carbons with controllable N defects was enabled by a newly developed approach through co-pyrolysis of Triton X-100 and conventional C 3 N 4 precursors. [Display omitted] [ABSTRACT FROM AUTHOR]