Expanded Sodalite-Type Metal−Organic Frameworks: Increased Stability and H₂ Adsorption through Ligand-Directed Catenation

The torsion between the central benzene ring and the outer aromatic rings in 1,3,5-tri-p-(tetrazol-5-yl)phenylbenzene (H3TPB-3tz) and the absence of such strain in 2,4,6-tri-p-(tetrazol-5-yl)phenyl-s-triazine (H3TPT-3tz) are shown to allow the selective synthesis of noncatenated and catenated versions of expanded sodalite-type metal−organic frameworks. The reaction of H3TPB-3tz with CuCl2·2H2O affords the noncatenated compound Cu3[(Cu4Cl)3(TPB-3tz)8]2·11CuCl2·8H2O·120DMF (2), while the reaction of H3TPT-3tz with MnCl2·4H2O or CuCl2·2H2O generates the catenated compounds Mn3[(Mn4Cl)3(TPT-3tz)8]2·25H2O·15CH3OH·95DMF (3) and Cu3[(Cu4Cl)3(TPT-3tz)8]2·xsolvent (4). Significantly, catenation helps to stabilize the framework toward collapse upon desolvation, leading to an increase in the surface area from 1120 to 1580 m2/g and an increase in the hydrogen storage capacity from 2.8 to 3.7 excess wt % at 77 K for 2 and 3, respectively. The total hydrogen uptake in desolvated 3 reaches 4.5 wt % and 37 g/L at 80 bar and 77 K, demonstrating that control of catenation can be an important factor in the generation of hydrogen storage materials

Expanded Sodalite-Type Metal−Organic Frameworks: Increased Stability and H₂ Adsorption through Ligand-Directed Catenation

The torsion between the central benzene ring and the outer aromatic rings in 1,3,5-tri-p-(tetrazol-5-yl)phenylbenzene (H3TPB-3tz) and the absence of such strain in 2,4,6-tri-p-(tetrazol-5-yl)phenyl-s-triazine (H3TPT-3tz) are shown to allow the selective synthesis of noncatenated and catenated versions of expanded sodalite-type metal−organic frameworks. The reaction of H3TPB-3tz with CuCl2·2H2O affords the noncatenated compound Cu3[(Cu4Cl)3(TPB-3tz)8]2·11CuCl2·8H2O·120DMF (2), while the reaction of H3TPT-3tz with MnCl2·4H2O or CuCl2·2H2O generates the catenated compounds Mn3[(Mn4Cl)3(TPT-3tz)8]2·25H2O·15CH3OH·95DMF (3) and Cu3[(Cu4Cl)3(TPT-3tz)8]2·xsolvent (4). Significantly, catenation helps to stabilize the framework toward collapse upon desolvation, leading to an increase in the surface area from 1120 to 1580 m2/g and an increase in the hydrogen storage capacity from 2.8 to 3.7 excess wt % at 77 K for 2 and 3, respectively. The total hydrogen uptake in desolvated 3 reaches 4.5 wt % and 37 g/L at 80 bar and 77 K, demonstrating that control of catenation can be an important factor in the generation of hydrogen storage materials

Expanded Sodalite-Type Metal−Organic Frameworks: Increased Stability and H₂ Adsorption through Ligand-Directed Catenation

The torsion between the central benzene ring and the outer aromatic rings in 1,3,5-tri-p-(tetrazol-5-yl)phenylbenzene (H3TPB-3tz) and the absence of such strain in 2,4,6-tri-p-(tetrazol-5-yl)phenyl-s-triazine (H3TPT-3tz) are shown to allow the selective synthesis of noncatenated and catenated versions of expanded sodalite-type metal−organic frameworks. The reaction of H3TPB-3tz with CuCl2·2H2O affords the noncatenated compound Cu3[(Cu4Cl)3(TPB-3tz)8]2·11CuCl2·8H2O·120DMF (2), while the reaction of H3TPT-3tz with MnCl2·4H2O or CuCl2·2H2O generates the catenated compounds Mn3[(Mn4Cl)3(TPT-3tz)8]2·25H2O·15CH3OH·95DMF (3) and Cu3[(Cu4Cl)3(TPT-3tz)8]2·xsolvent (4). Significantly, catenation helps to stabilize the framework toward collapse upon desolvation, leading to an increase in the surface area from 1120 to 1580 m2/g and an increase in the hydrogen storage capacity from 2.8 to 3.7 excess wt % at 77 K for 2 and 3, respectively. The total hydrogen uptake in desolvated 3 reaches 4.5 wt % and 37 g/L at 80 bar and 77 K, demonstrating that control of catenation can be an important factor in the generation of hydrogen storage materials

Expanded Sodalite-Type Metal−Organic Frameworks: Increased Stability and H₂ Adsorption through Ligand-Directed Catenation

The torsion between the central benzene ring and the outer aromatic rings in 1,3,5-tri-p-(tetrazol-5-yl)phenylbenzene (H3TPB-3tz) and the absence of such strain in 2,4,6-tri-p-(tetrazol-5-yl)phenyl-s-triazine (H3TPT-3tz) are shown to allow the selective synthesis of noncatenated and catenated versions of expanded sodalite-type metal−organic frameworks. The reaction of H3TPB-3tz with CuCl2·2H2O affords the noncatenated compound Cu3[(Cu4Cl)3(TPB-3tz)8]2·11CuCl2·8H2O·120DMF (2), while the reaction of H3TPT-3tz with MnCl2·4H2O or CuCl2·2H2O generates the catenated compounds Mn3[(Mn4Cl)3(TPT-3tz)8]2·25H2O·15CH3OH·95DMF (3) and Cu3[(Cu4Cl)3(TPT-3tz)8]2·xsolvent (4). Significantly, catenation helps to stabilize the framework toward collapse upon desolvation, leading to an increase in the surface area from 1120 to 1580 m2/g and an increase in the hydrogen storage capacity from 2.8 to 3.7 excess wt % at 77 K for 2 and 3, respectively. The total hydrogen uptake in desolvated 3 reaches 4.5 wt % and 37 g/L at 80 bar and 77 K, demonstrating that control of catenation can be an important factor in the generation of hydrogen storage materials

Expanded Sodalite-Type Metal−Organic Frameworks: Increased Stability and H₂ Adsorption through Ligand-Directed Catenation

The torsion between the central benzene ring and the outer aromatic rings in 1,3,5-tri-p-(tetrazol-5-yl)phenylbenzene (H3TPB-3tz) and the absence of such strain in 2,4,6-tri-p-(tetrazol-5-yl)phenyl-s-triazine (H3TPT-3tz) are shown to allow the selective synthesis of noncatenated and catenated versions of expanded sodalite-type metal−organic frameworks. The reaction of H3TPB-3tz with CuCl2·2H2O affords the noncatenated compound Cu3[(Cu4Cl)3(TPB-3tz)8]2·11CuCl2·8H2O·120DMF (2), while the reaction of H3TPT-3tz with MnCl2·4H2O or CuCl2·2H2O generates the catenated compounds Mn3[(Mn4Cl)3(TPT-3tz)8]2·25H2O·15CH3OH·95DMF (3) and Cu3[(Cu4Cl)3(TPT-3tz)8]2·xsolvent (4). Significantly, catenation helps to stabilize the framework toward collapse upon desolvation, leading to an increase in the surface area from 1120 to 1580 m2/g and an increase in the hydrogen storage capacity from 2.8 to 3.7 excess wt % at 77 K for 2 and 3, respectively. The total hydrogen uptake in desolvated 3 reaches 4.5 wt % and 37 g/L at 80 bar and 77 K, demonstrating that control of catenation can be an important factor in the generation of hydrogen storage materials

Impact of Preparation and Handling on the Hydrogen Storage Properties of Zn₄O(1,4-benzenedicarboxylate)₃ (MOF-5)

The prototypical metal-organic framework Zn4O(BDC)3 (MOF-5, BDC2- = 1,4-benzenedicarboxylate) decomposes gradually in humid air to form a nonporous solid. Recognizing this, improved procedures for its synthesis and handling were developed, leading to significant increases in N2 and H2 gas adsorption capacities. Nitrogen adsorption isotherms measured at 77 K reveal an enhanced maximum N2 uptake of 44.5 mmol/g and a BET surface area of 3800 m2/g, compared to the 35.8 mmol/g and 3100 m2/g obtained for a sample prepared using previous methods. High-pressure H2 adsorption isotherms show improvements from 5.0 to 7.1 excess wt % at 77 K and 40 bar. The total H2 uptake was further observed to climb to 11.5 wt % at 170 bar, corresponding to a volumetric storage density of 77 g/L. Thus, the air-free compound exhibits the highest gravimetric and volumetric H2 uptake capacities yet demonstrated for a cryogenic hydrogen storage material. Moreover, no loss of capacity was apparent during 24 complete adsorption−desorption cycles, while kinetics measurements showed a loading time of 2 min with application of just 45 bar of pressure

Synthesis and Hydrogen Storage Properties of Be₁₂(OH)₁₂(1,3,5-benzenetribenzoate)₄

Synthesis and Hydrogen Storage Properties of Be12(OH)12(1,3,5-benzenetribenzoate)4</sub

Synthesis and Hydrogen Storage Properties of Be₁₂(OH)₁₂(1,3,5-benzenetribenzoate)₄

Synthesis and Hydrogen Storage Properties of Be12(OH)12(1,3,5-benzenetribenzoate)4</sub

Kinetic Trapping of D₂ in MIL-53(Al) Observed Using Neutron Scattering

We have studied gas adsorption effects on the structure of a metal–organic framework, MIL-53­(Al), a material well-known because of the controllable framework “breathing” phenomenon. Neutron powder diffraction between 4 and 77 K and up to 4.5 bar pressure D₂ confirms that a structural phase transition is responsible for the observed H₂/D₂ isotherm hysteresis at 77 K. We find two crystallographically distinct D₂ adsorption sites in MIL-53­(Al) when the pores are fully opened, similar to those reported for D₂ in MIL-53­(Cr), but in contrast with the previously published cases of CO₂ and H₂O. Upon desorption of D₂ at 77 K, we find strong evidence for the existence of D₂ molecules kinetically trapped in the center of the closed pore of MIL-53­(Al). This “molecular clamp” appears to be functional until ≈120 K, the temperature at which the D₂ eventually desorbs under dynamic vacuum. Hydrogen diffusion constants calculated using quasielastic neutron scattering data collected along the isotherm are also consistent with H₂ being trapped in the closed pore structure. Diffraction experiments performed with N₂ and He gases under similar conditions show the range of structural response from immediate pore opening at low N₂ pressures (<1 bar) to no observable effect at 10 bar He

Hydrogen Storage in a Microporous Metal−Organic Framework with Exposed Mn²⁺ Coordination Sites

Use of the tritopic bridging ligand 1,3,5-benzenetristetrazolate (BTT3-) enables formation of [Mn(DMF)6]3[(Mn4Cl)3(BTT)8(H2O)12]2·42DMF·11H2O·20CH3OH, featuring a porous metal−organic framework with a previously unknown cubic topology. Crystals of the compound remain intact upon desolvation and show a total H2 uptake of 6.9 wt % at 77 K and 90 bar, which at 60 g H2/L provides a storage density 85% of that of liquid hydrogen. The material exhibits a maximum isosteric heat of adsorption of 10.1 kJ/mol, the highest yet observed for a metal−organic framework. Neutron powder diffraction data demonstrate that this is directly related to H2 binding at coordinatively unsaturated Mn2+ centers within the framework