Electrocatalysis of N2 to NH3 by HKUST‐1 with High NH3 Yield

Electrolytic ammonia synthesis from nitrogen at ambient conditions is appearing as a promising alternative to the Haber‐Bosch process which is consuming high energy and emitting CO₂. Here, a typical MOF material, HKUST‐1 (Cu?BTC, BTC=benzene‐1,3,5‐tricarboxylate), was selected as an electrocatalyst for the reaction of converting N₂ to NH₃ under ambient conditions. At ?0.75 V vs. reversible hydrogen electrode, it achieves excellent catalytic performance in the electrochemical synthesis of ammonia with high NH₃ yield (46.63 μg h^?1 mg^?1 _cat. or 4.66 μg h^?1 cm^?2) and good Faraday efficiency (2.45%). It is indicated that the good performance of the HKUST‐1 catalyst may originate from the formation of Cu(I). In addition, the catalyst also has good selectivity for N₂ to NH₃.     

WO3改性CeO2-TiO2催化剂的低温NH3-NO/NO2 SCR活性和机理研究

在铈钛基NH3-SCR催化材料中,改性元素对催化材料的酸性位和氧化还原性能的影响较大.本文采用过量浸渍法分别制备了CeO2-TiO2(CeTi)和CeO2/WO3-TiO2(CeWTi)催化剂,研究了CeWTi催化材料结构、酸性位及氧化还原性能对NH3-NO/NO2 SCR反应性能的影响.结果发现,CeTi和CeWTi样品均有较优异的NH3-NO/NO2 SCR催化性能,后者略高.WO3的加入增加了催化材料的表面酸性,对其氧化还原性能影响不大.通过对反应中间物种NH4NO3的研究,发现NH4NO3的分解主要与氧化还原性能相关,而NO还原NH4NO3的反应需要氧化还原能力和酸性位共同作用,即在氧化还原性能差异不大的条件下,酸性对该反应起到重要作用.而该反应也是NH3-NO/NO2 SCR的限速步骤,这是CeWTi催化材料活性高于CeTi催化材料的原因.同时,为了获得NH3-NO/NO2 SCR反应的高活性,NO2:NO比例宜为1:1.然而现实情况中,预氧化催化材料的氧化活性、NOx浓度、温度等变量使得准确控制NO2的比例较难,因此,深入了解NO2浓度对NH3–NO/NO2 SCR反应的影响至关重要.本文探讨NO2:NO的比例、O2浓度等对NH3-NO/NO2 SCR反应性能的影响;并研究了不同NO2含量条件下NH3-NO/NO2 SCR反应网络.通过分析CeWTi材料上NH3-NO/NO2 SCR反应网络可知,当NO与NO2比例为1:1时,NH3-SCR催化活性最高,并以快速SCR形式进行;当NO与NO2比例为1:1消耗完全之后,剩余的NO或NO2各自独立以标准或慢速SCR进行,不影响其本来的反应活性.催化材料的标准SCR、快速SCR和慢速SCR均取决于材料表面酸度和氧化还原性能,但快速SCR和慢速SCR对材料这两方面性能的要求相对较低.同时O2并不参与快速和慢速SCR,而NO2可以取代O2作为SCR反应中主要的氧化剂,氧化Ce4+为Ce3+,甚至比O2和NO再氧化活性位的能力更强,保持催化材料的高催化活性.低温条件时,慢速SCR和快速SCR反应均在材料表面生成硝酸铵中间物种,但由于慢速SCR气氛中缺乏NO将硝酸铵还原,进而引发快速SCR反应,因此材料表面快速SCR的NOx转化率要高于慢速SCR反应;高温条件下,由于硝酸铵容易热分解,导致硝酸铵的抑制效应不太明显.NH4NO3分解是NO2含量升高后N2O的形成的主要途径.     

High electrochemical activity of Pt/C cathode modified with NH4HCO3 for direct methanol fuel cell

The electrochemical activity of Pt/C cathode for direct methanol fuel cell was improved by introducing NH₄HCO₃ to the catalyst layer as the pore-forming agent during preparation process of catalyst-coated membrane. SEM analysis revealed that NH₄HCO₃ contributed to the formation of additional porosity and the dispersion of the catalyst particles. The modified catalyst layer promoted the electrochemical and mass transport processes. It was suggested that the optimal weight ratio of the catalyst to NH₄HCO₃ was 2:3. As a result, the single cell exhibited a 21% increment in the peak power density at 50 °C, with a highest electrochemical surface area of 446 cm² mg_Pt^–1. However, an extremely high content of NH₄HCO₃ yielded discontinuous pathways for the electron transfer in the catalyst layer.     

DyF3: An Efficient Electrocatalyst for N2 Fixation to NH3 under Ambient Conditions

NH₃ synthesis by the Haber–Bosch method is regarded as the dominant method in industry. Such a process is energy‐intensive, accompanied by a large amount of CO₂ emission. Electrocatalytic N₂ reduction is a sustainable avenue for NH₃ production at ambient conditions. However, it needs a catalyst to boost the N₂ reduction reaction. Here, we demonstrate that DyF₃ is an efficient electrocatalyst. In 0.1 m Na₂SO₄, DyF₃ attains a large NH₃ yield of 10.9 μg h^?1 mg^?1_cat. at ?0.45 V vs. the reversible hydrogen electrode, with the corresponding Faradaic efficiency of 8.8 %. Furthermore, this catalyst exhibits high electrochemical stability.     

Zwei Galliumfluorid-Ammoniakate: Ga(NH3)F3 und Ga(NH3)2F3

Two Gallium Fluoride Ammine Complexes: Ga(NH₃)F₃ and Ga(NH₃)₂F₃ Two gallium trifluoride ammines, Ga(NH₃)F₃ and Ga(NH₃)₂F₃, are obtained as single crystals through oxidation of gallium metal with NH₄HF₂ (Ga : NH₄HF₂ = 1 : 1.5) and NH₄F (Ga : NH₄F = 1 : 3.5), respectively, at 450 °C and 400 °C. Ga(NH₃)F₃ crystallizes with the non-centrosymmetric space group Abm2 (a = b = 544.6(2) pm, c = 986.6(4) pm) forming two-dimensional layers of [Ga(NH₃)F₅] octahedra. The addition of another NH₃ molecule in Ga(NH₃)₂F₃ (orthorhombic, Immm, a = 700.0(3) pm, b = 724.7(2) pm, c = 393.1(1) pm) leads to one-dimensional rods of [Ga(NH₃)₂F₄] octahedra running parallel [001] which are stacked in the [010] direction. Infrared spectra suggest hydrogen bonding (N–H…F) in Ga(NH₃)F₃, for Ga(NH₃)₂F₃ an unequivocal statement is not possible.     

Determination of NH(3) gas by combination of nanosized LaCoO(3) converter with chemiluminescence detector

Combination of a novel NH₃ converter based on nanosized materials with chemiluminescence (CL) detector for the determination of NH₃ gas was demonstrated in this paper. NH₃ gas is oxidized on different nanosized catalysts to produce NO_x, which can react with luminol to generate CL emission. Eight nanosized materials were investigated as catalyst, and CL was detected from seven of them. The nanosized LaCoO₃ was chosen as the catalyst for preparing the converter because of its higher activity than others. Under the optimized conditions, the linear range of CL intensity versus concentration of NH₃ gas is 0.04-10 ppm (r=0.9951, n=14) with the detection limit of 0.014 ppm. The method offers advantages of long lifetime of the converter, fast response and high selectivity to NH₃. There was no response while the foreign substances, such as hydrogen, oxygen, nitrogen, formaldehyde, acetone and gasoline passing through the CL detection system, and the interference of CCl₄, ethanol, ethylene and toluene was insignificant.     

NH3-SCR脱硝催化剂抗硫性能的研究进展

氮氧化物(NO_x)是一种重要的大气污染物, 它造成严重的环境问题, 同时威胁人类健康. 以钢铁烧结烟气为代表的固定源和以柴油机尾气为代表的移动源是氮氧化物的主要来源. 氨气选择性催化还原法(NH₃-SCR)是目前最有效且应用最广泛的NO_x脱除技术. 然而, 无论是固定源还是移动源上NH₃-SCR催化剂, 都不可避免地会被SO₂毒化, 造成催化剂失活, 限制了NH₃-SCR技术的进一步应用. 因此, 研究NH₃-SCR催化剂的SO₂中毒机制以及提高催化剂的抗硫性能至关重要. 我们对固定源脱硝的金属氧化物和移动源上脱硝的Cu基分子筛这两类不同催化剂体系的SO₂中毒机制的研究进展进行了介绍, 并对这两种催化剂上提高抗硫性能改性方法的研究进展进行了评述, 为未来的研究提供了参考.     

Zwei neue Ammoniakate des Scandiumtrichlorides,ScCl3(NH3) und ScCl3(NH3)2

Two New Ammoniates of Scandium Trichloride, ScCl₃(NH₃) and ScCl₃(NH₃)₂ Reactions of scandium with ammonium chloride in the presence of cupric chloride in sealed copper ampoules yield colorless single crystals of the two new ammoniates of scandium trichloride, ScCl₃(NH₃) und ScCl₃(NH₃)₂. The crystal structures were determined from single crystal data; they both crystallize with the triclinic crystal system. In ScCl₃(NH₃)₂ isolated unsymmetrical dimers of double octahedra, according to [Sc‐mer‐(NH₃)_3/1Cl_1/1Cl_(2/2)×2Sc(NH₃)_1/1Cl_3/1] are the characteristic structural features. The crystal structure of ScCl₃(NH₃) also contains double octahedra, [Sc(NH₃)_2/1Cl_2/1Cl_2/2]₂; these dimers are, however, connected via common edges forming infinite zig‐zag chains according to the formulation [Sc(NH₃)_1/1Cl_1/1Cl_4/2].     

Investigation of the promotion effect of Mo doped CuO catalysts for the low-temperature performance of NH3-SCR reaction

A novel Mo-doped CuO catalyst is developed and used for low-temperature NH₃-SCR reaction. Compared with the undoped CuO sample, the Mo doped CuO catalyst shows an increased SCR performance with above 80% NO_x conversion at 175 °C. The XRD and Raman results have confirmed the incorporation of Mo metal ions into CuO lattice to form Mo-O-Cu species which may be related to the enhanced SCR activity. The XPS and UV–vis results reveal the creation of electron interaction between Cu and Mo in this Mo-O-Cu system which provides an increased amount of Lewis and Brønsted acid sites, thereby promoting the adsorption capacity of NH₃ and NO_x as verified by NH₃-TPD and NO_x-TPD characterization. Besides, it also promotes the formation of oxygen vacancies, leading to the increasing of chemisorbed oxygen species, which improves the NO oxidation to NO₂ activity. Furthermore, in situ DRIFTS technology was also used to study the reaction mechanism of this Mo doped CuO catalyst. The formed NO₂ could react with NH_x (x = 3, 2) species to enhance the low-temperature NH₃-SCR activity via the “fast-SCR” reaction pathway. The nitrate and nitrite ad-species may react with NH₃ and NH₄⁺ ad-species through the L-H pathway.     

Ho改性的Mn-Ce/TiO2催化剂低温脱硝性能的评价和表征

作为引起酸雨、光化学烟雾、雾霾等大气污染问题的主要根源,氮氧化物(NOx)的防治已成为亟待解决的问题.选择性催化还原技术作为最成熟有效的脱硝技术,目前已经被广泛应用于各燃煤电厂.低温脱硝催化剂具有优秀的低温活性,使得脱硝装置可以安放在脱硫装置和除尘装置下游,受到了学者广泛的研究.目前低温脱硝催化剂的研究主要是对催化剂进行改性以提高催化剂的性能,已有许多研究报道了Sn、Ni、Co、Zr、Cr、Ni等对催化剂的改性影响.Ho作为一种改性元素被应用于光催化领域,能提高TiO2的光催化能力.但Ho应用于脱硝领域的研究鲜有报道,其氧化物具有酸性位点有助于脱硝反应,因此研究Ho对低温SCR催化剂的改性作用具有重要意义.本文采用浸渍法制备Ho掺杂的Mn-Ce/TiO2催化剂,研究了Ho的掺杂对于Mn-Ce/TiO2催化剂低温脱硝性能的影响,同时还研究了烟气中的SO2和H2O对催化剂活性的影响,并利用XPS、XRD、H2-TPR、NH3-TPD等表征方法从物理性质和化学性质两方面对Ho改性的影响机理进行了研究.研究发现,Ho的掺杂能提高Mn-Ce/TiO2催化剂的脱硝能力,有助于催化剂N2选择性的提高.分析表明,Ho的掺杂有助于催化剂比表面积的提升,且能提高催化剂的酸性,有利于催化剂对NH3的吸附,从而提高催化剂的性能.XPS表征结果表明Ho掺杂后的催化剂具有更高的化学吸附氧浓度和较高的Mn4+/Mn3+比例, 使得脱硝反应更容易进行.改性后催化剂的抗水抗硫实验结果表明,Ho的掺杂能够提高催化剂的抗水抗硫性能.XRD结果表明,抗水抗硫实验后催化剂表面形成了硫酸铵盐,硫酸铵盐的形成会堵塞催化剂表面的活性位,限制脱硝反应的进行,从而影响催化剂的脱硝活性.同时,400°C下进行再生实验后的催化剂活性有所恢复,但是未能达到抗水抗硫实验前的活性,表明在抗水抗硫实验中催化剂表面形成了除硫酸铵盐以外的其他硫酸盐类.结合XPS和XRD表征结果,推断生成的盐类物质为硫酸锰和硫酸铈,从而导致再生后的催化剂的脱硝活性无法恢复到最初的活性水平.由此可以看出,硫酸盐的形成是催化剂在含硫气氛中失活的主要原因.     

Synthese und Kristallstrukturen von NH4[Si(NH3)F5] und [Si(NH3)2F4]

Synthesis and Crystal Structures of NH₄[Si(NH₃)F₅] and [Si(NH₃)₂F₄] Single crystals of NH₄[Si(NH₃)F₅] and [Si(NH₃)₂F₄] are obtained by reaction of silicon powder with NH₄HF₂ in sealed Monel ampoules at 400°C. NH₄[Si(NH₃)F₅] crystallizes with the tetragonal space group P4/n (no. 85) with a = 614.91(7) pm, c = 721.01(8) pm, Z = 2. Characteristic for the structure is the anionic octahedron [Si(NH₃)F₅]^?. Si(NH₃)₂F₄ crystallizes with the monoclinic space group P2₁/c (no. 14) with a = 506.9(1) pm, b = 728.0(1) pm, c = 675.9(1), β = 93,21(2)°, Z = 2. Trans-[Si(NH₃)₂F₄] molecules are characteristic for this structure.     

Isotopic exchange of gaseous ammonia 14NH3 and 15NH3 in sulfonated macroreticular ion exchangers

Adsorption and ¹⁵NH₃ isotopic exchange was performed on dry macroreticular polystyrene ion exchanges crosslinked with varying amounts of divinylbenzene and partially neutralized by ¹⁴NH₃. Data on pressure changes and mass spectrometric analyses of isotopic composition of the gaseous phase were used to calculate equilibrium distribution of ¹⁴NH₃ and ¹⁵NH₃ under various dislocation conditions. It was established that along with the exchange of ¹⁴NH₃ to a gaseous phase, ¹⁵NH₃ penetrates to the mass of ion exchanger. This is evidently due to the migration of ammonia among functional groups. It was found that by thermal desorption under reduced pressure ammonia is released only from functional groups located on the surface of ion exchanger.     

WO_3对MnO_x-CeO_2/ZrO_2-TiO_2整体式催化剂NH_3选择性催化还原NO_x性能的影响

以ZrO2-TiO2为载体,MnOx-CeO2为活性组分,WO3为助剂制备了MnOx-CeO2/WO3/ZrO2-TiO2整体式催化剂,考察了添加不同质量分数的WO3对低温氨选择性催化还原(NH3-SCR)氮氧化物反应性能的影响.通过低温N2吸附-脱附,X射线衍射(XRD),X射线光电子能谱(XPS),NH3程序升温脱附(NH3-TPD)等手段对催化剂进行表征.实验结果表明,与未添加WO3的催化剂相比,含有10.0%(w)WO3的催化剂具有较好的织构性能,且具有较多的中强酸位,较好的氧化性能,表现出良好的NH3-SCR活性和较宽的活性温度窗口(空速为10000h-1时,在144-374℃之间,NOx转化率为90%以上),该催化剂在低温净化氮氧化物中具有潜在的应用前景.     

Crystal Structure of Ni(NH3)Cl2 and Ni(NH3)Br2

Ni(NH₃)Cl₂ and Ni(NH₃)Br₂ were prepared by the reaction of Ni(NH₃)₂X₂ with NiX₂ at 350 °C in a steel autoclave. The crystal structures were determined by X‐ray powder diffraction using synchrotron radiation and refined by Rietveld methods. Ni(NH₃)Cl₂ and Ni(NH₃)Br₂ are isotypic and crystallize in the space group I2/m with Z = 8 and for Ni(NH₃)Cl₂: a = 14.8976(3) Å, b = 3.56251(6) Å, c = 13.9229(3) Å, β = 106.301(1)°; Ni(NH₃)Br₂: a = 15.5764(1) Å, b = 3.74346(3) Å, c = 14.4224(1) Å, β = 105.894(1)°. The crystal structures are built up by two crystallographically distinct but chemically mostly equivalent polymeric octahedra double chains [NiX_3/3X_2/2(NH₃)] (X = Cl, Br) running along the short b‐axis. The octahedra NiX₅NH₃ share common edges therein. The crystal structures of the ammines Ni(NH₃)_mX₂ with m = 1, 2, 6 can be derived from that of the halides NiX₂ (X = Cl, Br) by successive fragmentation of its CdCl₂ like layers by NH₃.     

Das Monoammoniakat des Galliumamidfluorids: Ga(NH3)(NH2)F2

The Monoammoniate of Gallium Amide Fluoride, Ga(NH₃)(NH₂)F₂ The oxidation of gallium metal with NH₄F leads at 325 °C in the presence of indium to single crystals of Ga(NH₂)F₂ · NH₃ [monoclinic, C2/m (no. 12), a = 1053.1(1), b = 557.4(1), c = 484.2(3) pm, β = 90.04(4)]. The crystal structure is built up from layers of corner-bridged [Ga(NH₃)₂F₄] and [Ga(NH₂)₂F₄] octahedra, respectively. The infrared spectrum proves the existence of the amide group in Ga(NH₂)F₂ · NH₃.     

Monoammoniates of Aluminium Halides: The Crystal Structures of AlBr3 · NH3 and AlI3 · NH3

Single crystals of AlBr₃ · NH₃ and AlI₃ · NH₃ sufficient in size for X‐ray structure determinations were obtained by evaporation/ sublimation of the respective compound from its melt. The ammoniates were synthesized by the reaction of the pure halide with NH₃ at ‐78°C and following homogenization by slowly heating the reaction mixture up to the melting points of the ammoniates (124°C and 126°C, respectively). The X‐ray structure determinations for both monoammoniates were successfully carried out for the heavy atom positions (no hydrogen atoms): AlBr₃ · NH₃: Pbca, Z = 16, a = 11.529 (5) Å, b = 12.188 (2) Å, c = 19.701 (4) Å AlI₃ · NH₃: Pbca, Z = 8, a = 13.536 (5) Å, b = 8.759 (2) Å, c = 14.348 (4) Å The structures contain tetrahedral molecules Al(NH₃)X₃ with X = Br, I. They are not isotypic. The main difference is given for the coordination of NH₃ by X^‐ from neighbouring molecules. In Al(NH₃)Br₃ one of the two crystallographically independent NH₃ ligands has 6Br^‐ and the other 7Br^‐ as neighbours whereas in Al(NH)₃I₃ only 5I^‐ surround the one kind of NH₃.     

AlCl3 · 3NH3 — eine Verbindung mit der Kristallstruktur eines Tetraammindichloroaluminium-diammintetrachloroaluminats: [AlCl2(NH3)4]+[AlCl4(NH3)2]−

AlCl₃ · 3NH₃ — a Compound with the Crystal Structure of a Tetraammine Dichloro Aluminium-Diammine Tetrachloro Aluminate: [AlCl₂(NH₃)₄]⁺[AlCl₄(NH₃)₂]^? . AlCl₃ · 3 NH₃ ? [AlCl₂(NH₃)₄]⁺ [AlCl₄(NH₃)₂]^? forms during the reaction of two mole NH₃ with AlCl₃(NH₃) at T ≥ 200°C. Repeated heating and cooling within 48 h between 200°C and 250°C gives a homogeneous product with total uptake of the necessary amount of NH₃. Slow sublimation in a vacuum line apparatus at 200°C gives crystals of the triammoniate sufficient for a X-ray structure determination: The compound contains elongated [AlCl₂(NH₃)₄]⁺ octahedra and compressed [AlCl₄(NH₃)₂]^? octahedra. Besides ionic bonding hydrogen bridge bonds with 3.369 Å ? d(N—H … Cl) ? 3.589 Å stabilize the atomic arrangement.     

Metallampullen als Mini‐Autoklaven: Synthese und Kristallstrukturen der Ammoniakate [Al(NH3)4Cl2][Al(NH3)2Cl4] und (NH4)2[Al(NH3)4Cl2][Al(NH3)2Cl4]Cl2

Metal Ampoules as Mini‐Autoclaves: Syntheses and Crystal Structures of [Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄] and (NH₄)₂[Al(NH₃)₄Cl₂][Al(NH₃)₂Cl₄]Cl₂ The salts [Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–≡AlCl₃ · 3 NH₃ ( 1 ) and (NH₄⁺)²[Al(NH₃)₄Cl₂]⁺[Al(NH₃)₂Cl₄]^–(Cl^–)₂≡ AlCl₃ · 3 NH₃ · (NH₄)Cl ( 2 ) have been obtained as single crystals during the reactions of aluminum and aluminum trichloride, respectively, with ammonium chloride in sealed Monel metal containers. The crystal structure of 1 was determined again [triclinic, P‐1; a = 574.16(10); b = 655.67(12); c = 954.80(16) pm; α = 86.41(2); β = 87.16(2); γ = 84.89(2)°], that of 2 for the first time [monoclinic, I2/m; a = 657.74(12); b = 1103.01(14); c = 1358.1(3) pm; β = 103.24(2)°].     

Isotype Strukturen einiger Hexaamminmetall(II)-halogenide von 3d-Metallen: [V(NH3)6]I2, [Cr(NH3)6]I2, [Mn(NH3)6]Cl2, [Fe(NH3)6]Cl2, [Fe(NH3)6]Br2, [Co(NH3)6]Br2 und [Ni(NH3)6]Cl2

The Structures of some Hexaammine Metal(II) Halides of 3 d Metals: [V(NH₃)₆]I₂, [Cr(NH₃)₆]I₂, [Mn(NH₃)₆]Cl₂, [Fe(NH₃)₆]Cl₂, [Fe(NH₃)₆]Br₂, [Co(NH₃)₆]Br₂ and [Ni(NH₃)₆]Cl₂ Crystals of yellow [V(NH₃)₆]I₂ and green [Cr(NH₃)₆]I₂ were obtained by the reaction of VI₂ and CrI₂ with liquid ammonia at room temperature. Colourless crystals of [Mn(NH₃)₆]Cl₂ were obtained from Mn and NH₄Cl in supercritical ammonia. Colourless transparent crystals of [Fe(NH₃)₆]Cl₂ and [Fe(NH₃)₆]Br₂ were obtained by the reaction of FeCl₂ and FeBr₂ with supercritical ammonia at 400°C. Under the same conditions orange crystals of [Co(NH₃)₆]Br₂ were obtained from [Co₂(NH₂)₃(NH₃)₆]Br₃. Purple crystals of [Ni(NH₃)₆]Cl₂ were obtained by the reaction of NiCl₂ · 6H₂O and NH₄Cl with aqueous NH₃ solution. The structures of the isotypic compounds (Fm3 m, Z = 4) were determined from single crystal diffractometer data (see “Inhaltsübersicht”). All compounds crystallize in the K₂[PtCl₆] structure type. In these compounds the metal ions have high-spin configuration. The orientation of the dynamically disordered hydrogen atoms of the ammonia ligands is discussed.     

UF6 and UF4 in Liquid Ammonia: [UF7(NH3)]3− and [UF4(NH3)4]

From the reaction of uranium hexafluoride UF₆ with dry liquid ammonia, the [UF₇(NH₃)]^3? anion and the [UF₄(NH₃)₄] molecule were isolated and identified for the first time. They are found in signal‐green crystals of trisammonium monoammine heptafluorouranate(IV) ammonia (1:1; [NH₄]₃[UF₇(NH₃)] ? NH₃) and emerald‐green crystals of tetraammine tetrafluorouranium(IV) ammonia (1:1; [UF₄(NH₃)₄] ? NH₃). [NH₄]₃[UF₇(NH₃)] ? NH₃ features discrete [UF₇(NH₃)]^3? anions with a coordination geometry similar to a bicapped trigonal prism, hitherto unknown for U^IV compounds. The emerald‐green [UF₄(NH₃)₄] ? NH₃ contains discrete tetraammine tetrafluorouranium(IV) [UF₄(NH₃)₄] molecules. [UF₄(NH₃)₄] ? NH₃ is not stable at room temperature and forms pastel‐green [UF₄(NH₃)₄] as a powder that is surprisingly stable up to 147 °C. The compounds are the first structurally characterized ammonia complexes of uranium fluorides.