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

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