Highly Dense N–N-Bridged Dinitramino Bistriazole-Based 3D Metal–Organic Frameworks with Balanced Outstanding Energetic Performance

Due to the inherent conflict between energy and safety, the construction of energetic materials or energetic metal–organic frameworks (E-MOFs) with balanced thermal stability, sensitivity, and high detonation performance is challenging for chemists worldwide. In this regard, in recent times self-assembly of energetic ligands (high nitrogen- and oxygen-containing small molecules) with alkali metals were probed as a promising strategy to build high-energy materials with excellent density, insensitivity, stability, and detonation performance. Herein, based on the nitrogen-rich N,N′-([4,4′-bi(1,2,4-triazole)]-3,3′-dial)dinitramide (H2BDNBT) energetic ligand, two new environmentally benign E-MOFs including potassium [K2BDNBT]n (K-MOF) and sodium [Na2BDNBT]n (Na-MOF) have been introduced and characterized by NMR, IR, TGA-DSC, ICP-MS, PXRD, elemental analyses, and SCXRD. Interestingly, Na-MOF and K-MOF demonstrate solvent-free 3D dense frameworks having crystal densities of 2.16 and 2.14 g cm–3, respectively. Both the E-MOFs show high detonation velocity (VOD) of 8557–9724 m/s, detonation pressure (DP) of 30.41–36.97 GPa, positive heat of formation of 122.52–242.25 kJ mol–1, and insensitivity to mechanical stimuli such as impact and friction (IS = 30–40 J, FS > 360 N). Among them, Na-MOF has a detonation velocity (9724 m/s) superior to that of conventional explosives. Additionally, both the E-MOFs are highly heat-resistant, having higher decomposition (319 °C for K-MOF and 293 °C for Na-MOF) than the traditional explosives RDX (210 °C), HMX (279 °C), and CL-20 (221 °C). This stability is ascribed to the extensive structure and strong covalent interactions between BDNBT2– and K(I)/Na(I) ions. To the best of our knowledge, for the first time, we report dinitramino-based E-MOFs as highly stable secondary explosives, and Na-MOF may serve as a promising next-generation high-energy-density material for the replacement of presently used secondary thermally stable energetic materials such as RDX, HNS, HMX, and CL-20

Synthesis and Characterization of Polyhedral-Based Metal–Organic Frameworks Using a Flexible Bipyrazole Ligand: Topological Analysis and Sorption Property Studies

Six porous metal–organic frameworks (MOFs), {[Ni­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}_<i>n</i> (<b>1</b>), {[Co­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}<i>_n</i> (<b>2</b>), {[Mn­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}_<i>n</i> (<b>3</b>), {[Cd­(BDC)­(BPz)­(H₂O)]­·2MeOH­·DMF}<i>_n</i> (<b>4</b>), {[Cd₂(NH₂-BDC)₂­(BPz)­(H₂O)]­·MeOH­·H₂O­·DMF}<i>_n</i> (<b>5</b>), and {[Co­(BDC)­(BPz)­(H₂O)]}<i>_n</i> (<b>6</b>) (where H₃BTC = 1,3,5-benzenetricarboxylic acid, H₂BDC = 1,4-benzenedicarboxylic acid, NH₂-H₂BDC = 2-amino-1,4-benzenedicarboxylic acid, and BPz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole), were obtained through a solvent diffusion technique and characterized. The networks exhibit a variety of topologies: <b>1</b>, <b>2</b>, and <b>3</b> are isostructural and possess octahedral and cuboctahedra type cages and exhibit 3,6-c binodal net having <i><b>loh</b></i><b>1</b> topology, <b>4</b> is a two-dimensional MOF having one-dimensional open channels with a 4-c uninodal net having <i><b>sql</b></i> topology, <b>5</b> exhibits a three-dimensional (3D) porous MOF having a 3,3,4,8-c net with a new topology having the name, <i><b>skr</b></i><b>1</b>, whereas <b>6</b> discloses a 3D nonporous network which exhibits a 4-c uninodal net having CdSO₄ topology. Being isostructural, gas sorption studies of <b>1</b>–<b>3</b> show nearly the same CO₂ sorption at 195 K of ∼90 mL g^–1, whereas <b>4</b> and <b>5</b> show a maximum uptake of 42 and 37 mL g^–1 at 195 K. Vapor sorption studies of <b>1</b>–<b>3</b> reveal stepwise uptake of water with a final amount reached to nearly 350 mL g^–1, whereas <b>4</b> and <b>5</b> show maximum uptake of 110 and 90 mL g^–1, respectively. Compared to the free ligand BPz, photoluminescence studies of <b>4</b> and <b>5</b> show red shifts and emit in the blue-green region with λ_max at 430 and 472 nm for <b>4</b> and <b>5</b>, respectively

Synthesis and Characterization of Polyhedral-Based Metal–Organic Frameworks Using a Flexible Bipyrazole Ligand: Topological Analysis and Sorption Property Studies

Six porous metal–organic frameworks (MOFs), {[Ni­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}_<i>n</i> (<b>1</b>), {[Co­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}<i>_n</i> (<b>2</b>), {[Mn­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}_<i>n</i> (<b>3</b>), {[Cd­(BDC)­(BPz)­(H₂O)]­·2MeOH­·DMF}<i>_n</i> (<b>4</b>), {[Cd₂(NH₂-BDC)₂­(BPz)­(H₂O)]­·MeOH­·H₂O­·DMF}<i>_n</i> (<b>5</b>), and {[Co­(BDC)­(BPz)­(H₂O)]}<i>_n</i> (<b>6</b>) (where H₃BTC = 1,3,5-benzenetricarboxylic acid, H₂BDC = 1,4-benzenedicarboxylic acid, NH₂-H₂BDC = 2-amino-1,4-benzenedicarboxylic acid, and BPz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole), were obtained through a solvent diffusion technique and characterized. The networks exhibit a variety of topologies: <b>1</b>, <b>2</b>, and <b>3</b> are isostructural and possess octahedral and cuboctahedra type cages and exhibit 3,6-c binodal net having <i><b>loh</b></i><b>1</b> topology, <b>4</b> is a two-dimensional MOF having one-dimensional open channels with a 4-c uninodal net having <i><b>sql</b></i> topology, <b>5</b> exhibits a three-dimensional (3D) porous MOF having a 3,3,4,8-c net with a new topology having the name, <i><b>skr</b></i><b>1</b>, whereas <b>6</b> discloses a 3D nonporous network which exhibits a 4-c uninodal net having CdSO₄ topology. Being isostructural, gas sorption studies of <b>1</b>–<b>3</b> show nearly the same CO₂ sorption at 195 K of ∼90 mL g^–1, whereas <b>4</b> and <b>5</b> show a maximum uptake of 42 and 37 mL g^–1 at 195 K. Vapor sorption studies of <b>1</b>–<b>3</b> reveal stepwise uptake of water with a final amount reached to nearly 350 mL g^–1, whereas <b>4</b> and <b>5</b> show maximum uptake of 110 and 90 mL g^–1, respectively. Compared to the free ligand BPz, photoluminescence studies of <b>4</b> and <b>5</b> show red shifts and emit in the blue-green region with λ_max at 430 and 472 nm for <b>4</b> and <b>5</b>, respectively

All-optical spin injection in silicon investigated by element-specific time-resolved Kerr effect

Understanding howa spin current flows across metal-semiconductor interfaces at pico- and femtosecond time scales is of paramount importance for ultrafast spintronics, data processing, and storage applications. However, the possibility to directly access the propagation of spin currents, within such time scales, has been hampered by the simultaneous lack of both ultrafast element-specific magnetic sensitive probes and tailoredwell-built and characterized metal-semiconductor interfaces. Here, by means of a novel free-electron laser-based element-sensitive ultrafast time-resolved Kerr spectroscopy, we reveal different magnetodynamics for the Ni M-2;3 and Si L-2;3 absorption edges. These results are assumed to be the experimental evidence of photoinduced spin currents propagating at a speed of similar to 0.2 nm/fs across the Ni/Si interface