Supramolecular Cobaloxime Assemblies for H₂ Photocatalysis: An Initial Solution State Structure−Function Analysis

In this report, we have investigated the correlations between structure and light-induced electron transfer of one known and three new axially coordinated cobaloxime-based supramolecular photocatalysts for the reduction of protons to hydrogen. Solution-phase X-ray scattering and ultrafast transient optical spectroscopy analyses were used in tandem to correlate the self-assembled photocatalysts’ structural integrity in solution with electron transfer and charge separation between the photosensitizer and catalyst fragments. Biphasic excited state decay kinetics were observed for several of the assemblies, suggesting that configurational dispersion plays a role in limiting photoinduced electron transfer. Notably, an assembly featuring a “push−pull” donor−photosensitizer−acceptor triad motif exhibits considerable ultrafast excited state quenching and, of the assemblies examined, presents the strongest opportunity for efficient solar energy conversion. These results will assist in the design and development of next-generation supramolecular photocatalyst architectures

Chemical Reduction of Metal−Organic Framework Materials as a Method to Enhance Gas Uptake and Binding

A mixed-ligand metal−organic framework (MOF) of the formula Zn2(NDC)2(diPyNI) (NDC = 2,6-dicarboxylate, diPyNI = N,N‘-di-(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide) has been chemically reduced in the solid state by lithium metal in dimethylformamide (DMF). Striking hysteresis in the N2 adsorption isotherm suggests dynamic framework behavior of the reduced material that is not observed in the neutral MOF. The reduced framework also exhibits significantly enhanced H2 uptake and isosteric heat of adsorption over the entire loading range. Notably, the striking increase in H2 uptake cannot be solely attributed to H2−Li+ interactions and is most likely augmented by increased ligand polarizability and framework displacement effects

An Example of Node-Based Postassembly Elaboration of a Hydrogen-Sorbing, Metal−Organic Framework Material

A robust, noncatenated, and permanently microporous metal−organic framework (MOF) material has been synthesized by combining a new nonplanar ligand, 4,4′,4′′,4′′′-benzene-1,2,4,5-tetrayltetrabenzoic acid, with a zinc(II) source under solvothermal conditions. The new material features cavities that are readily modified via activation and functionalization of framework nodes (as opposed to struts). A preliminary investigation of the “empty cavity” version of the material and six cavity-modified versions reveals that modification can substantially modulate the MOF’s internal surface area, pore volume, and ability to sorb molecular hydrogen

Microporous Pillared Paddle-Wheel Frameworks Based on Mixed-Ligand Coordination of Zinc Ions

The reaction of Zn(NO3)2·6H2O, various dicarboxylic acids, and either 4,4‘-bipyridine or N,N‘-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas

Microporous Pillared Paddle-Wheel Frameworks Based on Mixed-Ligand Coordination of Zinc Ions

The reaction of Zn(NO3)2·6H2O, various dicarboxylic acids, and either 4,4‘-bipyridine or N,N‘-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas

Microporous Pillared Paddle-Wheel Frameworks Based on Mixed-Ligand Coordination of Zinc Ions

The reaction of Zn(NO3)2·6H2O, various dicarboxylic acids, and either 4,4‘-bipyridine or N,N‘-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas

An Example of Node-Based Postassembly Elaboration of a Hydrogen-Sorbing, Metal−Organic Framework Material

A robust, noncatenated, and permanently microporous metal−organic framework (MOF) material has been synthesized by combining a new nonplanar ligand, 4,4′,4′′,4′′′-benzene-1,2,4,5-tetrayltetrabenzoic acid, with a zinc(II) source under solvothermal conditions. The new material features cavities that are readily modified via activation and functionalization of framework nodes (as opposed to struts). A preliminary investigation of the “empty cavity” version of the material and six cavity-modified versions reveals that modification can substantially modulate the MOF’s internal surface area, pore volume, and ability to sorb molecular hydrogen

Microporous Pillared Paddle-Wheel Frameworks Based on Mixed-Ligand Coordination of Zinc Ions

The reaction of Zn(NO3)2·6H2O, various dicarboxylic acids, and either 4,4‘-bipyridine or N,N‘-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas

Microporous Pillared Paddle-Wheel Frameworks Based on Mixed-Ligand Coordination of Zinc Ions

The reaction of Zn(NO3)2·6H2O, various dicarboxylic acids, and either 4,4‘-bipyridine or N,N‘-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas

Microporous Pillared Paddle-Wheel Frameworks Based on Mixed-Ligand Coordination of Zinc Ions

The reaction of Zn(NO3)2·6H2O, various dicarboxylic acids, and either 4,4‘-bipyridine or N,N‘-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas