Jianping Guo

The synthesis of organic nitriles remains heavily dependent on methodologies that often involve transition-metal catalysts or toxic cyanide reagents, limiting their sustainability. Here, we report a cyanide- and transition-metal-free chemical looping strategy that converts α-aryl alkenes and ammonia (NH3) into α-aryl nitriles using potassium amide (KNH2) as a reaction mediator. The reaction initially proceeds via the formation of α-aryl nitrile potassium salts. Subsequent treatment of the potassium salts with NH3 liberates nitriles and regenerates KNH2, thereby closing the chemical loop. Combined experimental characterizations and computational results reveal an initial nucleophilic amide-mediated anti-Markovnikov addition followed by a K+-facilitated dehydrogenation process. Two synergistic effects stabilize the key carbanionic intermediates: carbanion-phenyl conjugation and tridentate coordination of K+. Owing to stronger conjugation among the phenyl rings, the central carbanion, and the cyano group, the product carbanion is energetically more stable than the precursor carbanion, which constitutes the thermodynamic driving force for the overall dehydrogenation. This atom-economical approach redefines alkali metal amides as versatile reagents for sustainable nitrogen-atom transfer.

Photothermal catalysis offers a promising pathway for sustainable ammonia synthesis under mild conditions. However, its performance is constrained by intrinsic scaling relations between dinitrogen activation and subsequent hydrogenation steps. To overcome this long-standing bottleneck, we design a Ru-LiH/TiN catalyst that enables a light-driven reaction cascade, wherein lithium hydride (LiH) serves as a dynamic “nitrogen mediator”. Under ambient pressure and illumination at 3.3 W·cm–2, the catalyst achieves an unprecedented NH3 production rate of 5574.3 μmol·g–1·h–1 (equivalent to 428.8 mmol·gRu–1·h–1), representing a 31-fold improvement over its thermal-catalytic counterpart and a 52-fold enhancement relative to Ru/TiN. Notably, the Ru-LiH/TiN exhibits robust catalytic stability over 50 h, in stark contrast to the rapid deactivation (<1 h) commonly observed in thermal catalysis due to NHx (x = 1–3) accumulation-induced adsorbate poisoning. Mechanistic studies reveal a relayed photothermal catalysis mechanism: photogenerated hot electrons facilitate N2 activation on Ru sites, followed by nitrogen transfer to the LiH-TiN interface to form destabilized [Li–Ti–N-H] intermediates; subsequently, photoexcited LiH liberates reactive hydrogen species that participate in nitrogen hydrogenation. This work presents a new strategy that simultaneously weakens the strong adsorption of NHx on the catalyst and enables efficient NH3 production under mild conditions.

Plasma‐catalytic ammonia synthesis is an emerging alternative approach for the sustainable conversion of dinitrogen (N ₂ ) to ammonia (NH ₃ ) using renewable electricity. However, the development of efficient catalysts for plasma‐driven ammonia synthesis remains a formidable challenge. Herein, we report that calcium imide (CaNH) functions as an active, transition‐metal‐free catalyst for plasma‐driven ammonia synthesis. Under 25 W and 20 kHz dielectric barrier discharge (DBD) conditions, the ammonia synthesis rate over CaNH is approximately three times that of the blank test, representing a performance enhancement comparable to the widely studied benchmark Ni/Al ₂ O ₃ catalyst. Combined experimental and computational results reveal that the CaNH surface, with plasma‐generated coordinatively unsaturated calcium sites, plays a critical role in promoting the hydrogenation of N _x H _y species to generate NH ₃ rather than in the activation of N ₂ —thus redefining the rate‐determining step. This study unveils a new functionality of alkaline earth metal imides in plasma‐catalytic ammonia synthesis, thereby offering greater opportunities for the development of new materials and active catalysts. Furthermore, this work provides new insights into the catalytic mechanism of other catalysts for plasma‐catalytic ammonia synthesis.

Ammonia is an essential chemical feedstock and a promising hydrogen energy carrier, motivating the development of efficient ammonia synthesis catalysts. However, scaling relations fundamentally limit conventional transition metal‐based catalysts, rendering strongly N ₂ ‐binding metals such as Mn ineffective due to sluggish hydrogenation. Herein, we demonstrate that atomically dispersed Mn (Mn ₁ ) anchored on the ternary hydride LiBaH ₃ (LiBaH ₃ ─Mn ₁ ) enables efficient ammonia synthesis via an H ⁻ ion‐assisted N ₂ dissociation mechanism. The MgO supported LiBaH ₃ ─Mn ₁ catalyst (LiBaH ₃ ─Mn ₁ /MgO) exhibits an ammonia synthesis rate two orders of magnitude higher than that of manganese nitride and exceeds the benchmark Cs─Ru/MgO catalyst by a factor of 2.5 at 400°C, representing a state‐of‐the‐art performance among group 4–7 transition metal–based catalysts. Mechanistic investigations reveal that Mn ₁ serves as the active site for N ₂ adsorption, while H ⁻ ions from LiBaH ₃ further activate the adsorbed *N ₂ through a reductive protonation process to form *N ₂ H intermediates. Subsequent N─N bond cleavage of *N ₂ H yields surface nitride (Mn─N) and imide (*NH) species on the LiBaH ₃ ─Mn ₁ surface. This H ⁻ ion‐assisted N ₂ dissociation pathway fundamentally overcomes the intrinsic limitations of bulk Mn, transforming it into an efficient metal for ammonia synthesis.

Ammonia is an essential chemical feedstock and a promising hydrogen energy carrier, motivating the development of efficient ammonia synthesis catalysts. However, scaling relations fundamentally limit conventional transition metal‐based catalysts, rendering strongly N ₂ ‐binding metals such as Mn ineffective due to sluggish hydrogenation. Herein, we demonstrate that atomically dispersed Mn (Mn ₁ ) anchored on the ternary hydride LiBaH ₃ (LiBaH ₃ ─Mn ₁ ) enables efficient ammonia synthesis via an H ⁻ ion‐assisted N ₂ dissociation mechanism. The MgO supported LiBaH ₃ ─Mn ₁ catalyst (LiBaH ₃ ─Mn ₁ /MgO) exhibits an ammonia synthesis rate two orders of magnitude higher than that of manganese nitride and exceeds the benchmark Cs─Ru/MgO catalyst by a factor of 2.5 at 400°C, representing a state‐of‐the‐art performance among group 4–7 transition metal–based catalysts. Mechanistic investigations reveal that Mn ₁ serves as the active site for N ₂ adsorption, while H ⁻ ions from LiBaH ₃ further activate the adsorbed *N ₂ through a reductive protonation process to form *N ₂ H intermediates. Subsequent N─N bond cleavage of *N ₂ H yields surface nitride (Mn─N) and imide (*NH) species on the LiBaH ₃ ─Mn ₁ surface. This H ⁻ ion‐assisted N ₂ dissociation pathway fundamentally overcomes the intrinsic limitations of bulk Mn, transforming it into an efficient metal for ammonia synthesis.

Photocatalytic nitrogen (N₂) reduction offers a renewable route for mild-condition ammonia (NH₃) synthesis and has garnered increasing attention. Most efforts have focused on tailoring the band structures of photocatalysts, yet the photon-responsive behavior of key reactive intermediates (such as NH and NH₂) that could have a strong impact on the energetics of individual steps has remained essentially uninvestigated primarily due to their low abundance and high lability. Herein, we report a transition-metal-free lithium hydride (LiH) catalyst that forms detectable lithium hydride with hydrogen vacancies (LiH_1-x), lithium imide (Li₂NH), and lithium amide (LiNH₂) intermediate states during NH₃ formation and therefore exhibits dynamic photoresponsive behaviors. This catalyst provides an ideal platform to investigate the wavelength-tailored regulation of intermediates in this bellwether reaction of catalysis. Specifically, ultraviolet light activates LiH for N₂ reduction, forming LiH_1-x, Li₂NH, and LiNH₂ species. Those species/states can absorb ultraviolet and visible light, enabling efficient H₂ dissociation and sequential hydrogenation to produce NH₃. In this unique scenario, the reaction energetics of individual steps are wavelength dependent, thus decoupling the scaling relations that constrain thermal catalysis. Such a cumulative photon effect on the catalyst and reactive species leads to a prominent NH₃ concentration of ca. 0.25%, exceeding the thermodynamic limit of 0.13% at 644 K and atmospheric pressure.