The emergence of zerovalent atom catalysts has been highly attractive for catalytic science. For many years, scientists have explored the stability of zerovalent atom catalysts and demonstrated their unique properties. Here, we describe an atom catalyst (AC) with atomically dispersed zerovalent molybdenum atoms on graphdiyne (Mo 0 /GDY) with a high mass content of Mo atoms (up to 7.5 wt %) that was synthesized via a facile and scalable process. The catalyst shows both excellent selectivity and activity in the electrochemical reduction of nitrogen and in the hydrogen evolution reaction in aqueous solutions at room temperature and pressure. It is noted that this catalyst is the first bifunctional AC for highly efficient and selective ammonia and hydrogen generation. The catalytic process of our catalyst is well understood, the structure is defined, and the performance is excellent, providing a solid foundation for the generation and application of the new generation of catalysts.

The generation of intense coherent deep-UV light from nonlinear optical materials is crucial to applications ranging from semiconductor photolithography and laser micromachining to photochemical synthesis. However, few materials with large second harmonic generation (SHG) and a short UV-cutoff edge are effective down to 200 nm. A notable exception is KBe2BO3F2, which is obtained from a solid-state reaction of highly toxic beryllium oxide powders. We designed and synthesized a benign polar material, Ba4B11O20F, that satisfies these requirements and exhibits the largest SHG response in known borates containing neither lone-pair-active anions nor second-order Jahn-Teller-active transition metals. We developed a microscopic model to explain the enhancement, which is unexpected on the basis of conventional anionic group theory arguments. Crystal engineering of atomic displacements along the polar axis, which are difficult to attribute to or identify within unique anionic moieties, and greater cation polarizabilities are critical to the design of next-generation SHG materials.

Deep ultraviolet (absorption edge <200 nm, band gap >6.2 eV) nonlinear optical (NLO) materials are of current interest owing to their technological applications and materials design challenges. Technologically, the materials are used in laser systems, atto-second pulse generation, semiconductor manufacturing, and photolithography. Designing and synthesizing a deep UV NLO material requires crystallographic noncentrosymmetry, a wide UV transparency range, a large second-harmonic generating coefficient (d ij > 0.39 pm/V), moderate birefringence (Δn ∼ 0.07), chemical stability and resistance to laser damage, and ease in the growth of large high-quality single crystals. This review examines the known deep UV NLO materials with respect to their crystal structure, band gap, SHG efficiency, laser damage threshold, and birefringence. Finally, future directions with respect to new deep UV NLO materials are discussed.

Photo-labile molecules have been widely used not only in organic synthesis but also in biological study. The chemistry of the typical photo-labile organic molecules, including their structure, mechanism underlying their photo-lability and strategies to integrate them with biomolecules, is reviewed to illustrate the structural basis for photo-activable caged compounds. Biological applications of representative photo-labile caged molecules were also illustrated for a general understanding on the important roles of caged compounds in dynamic biological studies. This tutorial review would provide an interdisciplinary overview on the important area of chemical biological study making use of photo-labile caged compounds.

The generation of deep-ultraviolet (UV) coherent light from nonlinear optical (NLO) materials [1][2][3][4] as one of the most promising resource, has become a topic of intensive study because of its important applications in a broad range of fields, such as semiconductor photolithography, laser micromachining, photochemical synthesis, and material processing. They are able to shorten the wavelength of light by a factor of two (or doubling the frequency), based on the process of second-harmonic generation (SHG), which occurs only when a centrosymmetric symmetry operation is absent in a crystal. However, for a noncentrosymmetric (NCS) crystal to be used as a nonlinear optical material the essential crystal property requirements are that the crystals possess a large NLO response, wide transparent window, suitable birefringence for phase-matching, good mechanical strength, and chemical stability. [4,5] After continuous efforts over several decades, many NCS compounds were obtained by incorporating functional borate structure units, such as B 3 O 6 and B 3 O 7 . b-BaB 2 O 4 (BBO) [6] and LiB 3 O 5 (LBO) [7] are the most advanced NLO materials, which have widely been used as optoelectronic devices. However, to date, KBe 2 BO 3 F 2 (KBBF) [8,9] is the only material that can generate coherent light wavelengths below 200 nm by direct SHG, which makes KBBF a research hotspot. Unfortunately, the KBBF crystal is very difficult to grow in thickness owing to the growth habit of the layer, which severely limits the coherent light output power. Thus, finding the optimal composition that is facile to synthesize, yields large single crystals, and simultaneously satisfies the NLO requirements has attracted considerable attention. [10,11] The presence of large NLO coefficients in a structure is usually in contradiction with wide band gaps in one compound. For instance, the structural units in the known compounds are second-order Jahn-Teller (SOJT) polar dis- [17] which combine with diverse other functional building units to produce materials with large NLO coefficients, for example, Cd 4 BiO-(BO 3 ) 3 (6 KDP), [18] Pb 2 B 5 O 9 I (13.5 KDP), [19] and Ba 23 Ga 8 Sb 2 S 38 (22 AgGaS 2 ).[20] However, the structural units produce an unwanted effect-the UV absorption edge shifts toward the red region, making them less suitable for the deep-UV applications. It is necessary to create the subtle balance of above-mentioned conflicting factors so as to search for the new deep-UV NLO crystals with excellent comprehensive performances.To circumvent the wide absorption window requirement, basic structural units having excitation energies near the UV region are necessary. Such units are BO 3 , BO 4 , SiO 4 , and PO 4 . [6,7,21] A compound Rb 2 Be 2 Si 2 O 7 [22] was ever expected to be a substitution for KBBF owing to its similar structure characteristics with KBBF and without the layer habit. But, the weak SHG response of Rb 2 Be 2 Si 2 O 7 makes the substitution end in naught. However, the borosilicate may be a potential candidate for a deep-...

On the basis of their short ultraviolet (UV) absorption edges, phosphates are ideal candidates for deep-UV nonlinear optical (NLO) applications. However, their often-weak second-harmonic generating (SHG) responses reduce their NLO applications. It has been demonstrated that the SHG response in polyphosphates or orthophosphates could be enhanced by highly polymerized P−O groups or aligned nonbonding O-2p orbitals of isolated PO 4 units. Herein, we report on the design and synthesis of two pyrophosphates, K 4 Mg 4 (P 2 O 7 ) 3 and Rb 4 Mg 4 (P 2 O 7 ) 3 , with potential NLO applications. Both materials exhibit relatively large SHG responses with 1064 nm radiation, 1.3× and 1.4× KH 2 PO 4 (KDP) for K 4 Mg 4 (P 2 O 7 ) 3 and Rb 4 Mg 4 (P 2 O 7 ) 3 , respectively. In addition, absorption edges below 200 nm were observed for both materials. For K 4 Mg 4 (P 2 O 7 ) 3 , single crystal vacuum-UV transmission measurements revealed an absorption edge of 170 nm. First-principles electronic structure calculations identify that the NLO responses arise from the presence of the corner-connected [Mg 4 P 6 O 21 ] double layers. We also investigated these compounds using hybrid density functionals, which are found to produce much better agreement with the experimental optical results. Finally, we detail the structural distortions giving rise to the NLO responses. Our results indicate that phosphates with low polymerized P−O groups, such as pyrophosphates, may exhibit large SHG responses if their structures are properly designed.

SummaryAtomic catalysts are promising alternatives to bulk catalysts for the hydrogen evolution reaction (HER), because of their high atomic efficiencies, catalytic activities, and selectivities. Here, we report the ultrathin nanosheet of graphdiyne (GDY)-supported zero-valent palladium atoms and its direct application as a three-dimensional flexible hydrogen-evolving cathode. Our theoretical and experimental findings verified the successful anchoring of Pd0 to GDY and the excellent catalytic performance of Pd0/GDY. At a very low mass loading (0.2%: 1/100 of the 20 wt % Pt/C), Pd0/GDY required only 55 mV to reach 10 mA cm−2 (smaller than 20 wt % Pt/C); it showed larger mass activity (61.5 A mgmetal−1) and turnover frequency (16.7 s−1) than 20 wt % Pt/C and long-term stability during 72 hr of continuous electrolysis. The unusual electrocatalytic properties of Pd0/GDY originate from its unique and precise structure and valence state, resulting in reliable performance as an HER catalyst.

Graphdiyne (GDY), a novel one‐atom‐thick carbon allotrope that features assembled layers of sp‐ and sp2‐hybridized carbon atoms, has attracted great interest from both science and industry due to its unique and fascinating structural, physical, and chemical properties. GDY‐based materials with different morphologies, such as nanowires, nanotube arrays, nanosheets, and ordered stripe arrays, have been applied in various areas such as catalysis, solar cells, energy storage, and optoelectronic devices. After an introduction to the fundamental properties of GDY, recent advances in the fabrication of GDY‐based nanostructures and their applications, and corresponding mechanisms, are covered, and future critical perspectives are also discussed.