The ample choice of organic ligand and series of available metal ions offer a library of metal–organic frameworks (MOFs) to be designed, synthesized, and applied for various interesting applications. ...However, the way to achieve complete control over the formation of desired architectures and properties is still an elusive goal. Several factors often directly or indirectly influence the synthesis of MOFs such as nature of solvent, pH, temperature, reactant stoichiometry, concentration of precursors, counterions, etc. These parameters are crucial for the formation of the crystalline product in the first place and also dictate the overall network dimension or topology. Herein, we have synthesized six Zn(II)/ Co(II)/ Cu(II) based MOFs and rationalized the effect of the presence of polar protic solvents like water/ethanol in directing the overall network dimension. The presence of polar protic solvents like ethanol/water resulted in the formation of secondary building units (SBUs) that directs the network to extend on a plane while the absence/scarcity of such solvents leads to a different SBU that facilitate propagation of the network in three dimensions. Such variation was attributed to the competitive coordination ability of such solvents and the extent of hydrogen bonding with the ligand.
Metal–organic frameworks (MOFs) are emerging as highly promising candidates for the next-generation proton conductors. Particularly, the amine-containing as well as various acid-functionalized MOFs ...and coordination polymers have been well explored. In anticipation of producing an alternate proton-conducting material with superior proton conductivity, both amine and sulfonates were incorporated in a MOF (Cu-SAT). It exhibits high stability in water, stability to dilute hydrochloric acid, and a remarkable proton conductivity of 0.53 × 10–3 S cm–1 at 353 K and 98% RH. As a step toward the practical application of the material in proton exchange membrane fuel cells (PEMFCs), the composite membranes of Cu-SAT and poly(vinylidene fluoride) (PVDF)−poly(vinylpyrrolidone) (PVP) matrix have been further fabricated. These PEMs display a proton conductivity as high as 0.80 × 10–3 S cm–1 at 353 K and 98% RH.
Coordination polymers (CPs) and metal–organic frameworks (MOFs) have emerged as promising materials for the photocatalytic hydrogen evolution reaction (HER). The flexibility to choose the organic ...linkers or the metal center provides the scope to alter their various properties like light absorption capability, optical band gap, etc. In this context, the dye molecules are the best choice to be utilized as a linker due to their ability to absorb visible light. However, the CPs/MOFs containing the dye molecules as a backbone are rarely explored. Herein, two isostructural fluorescein-based CPs were reported and shown to be efficient photocatalysts for the HER under white light without using a cocatalyst or a sensitizer. Here, the dye molecule was strategically incorporated into the backbone of the CPs, Cd(FC)(BPY)(H2O) n (Cd-FCB) and Mn(FC)(BPY)(H2O) n (Mn-FCB), and their efficiency as photocatalysts were explored. The band gap of the isostructural CPs was found to have a huge effect on their photocatalytic efficiency. The rate of hydrogen production was 71.6 μmol g–1 h–1 for Cd-FCB, and for Mn-FCB, it was three times higher, i.e., 224.1 μmol g–1 h–1. The higher efficiency can be attributed to the extended visible light absorption as well as the lower band gap of Mn-FCB than that of Cd-FCB. Moreover, the longer lifetime of the photogenerated electrons in Mn-FCB as indicated by the time-resolved photoluminescence spectra also validates such higher activity.
Coordination polymers (CPs) have received great attention as promising proton-conducting materials because of easy functionalization and structural tunability. However, studies of proton-conducting ...CPs illustrating the structure–property correlation are limited. The present study is focused on the synthesis of two one-dimensional CPs of copper(II) and cadmium(II) with NO3 – and SO4 2– anions, respectively. The former with nitrate anions shows interdigitated 1D chains with channels of disordered water molecules, while the crystal packing of the other shows 1D zigzag polymers with a network of coordinated water molecules and sulfate ions that provides a synergic effect to enhance the proton transport property. We have delineated the structure–property relationship by analyzing the effects of these structural differences on their proton conductivity.
The synthesis of reversible oligomer/polymers is fascinating both from the perspective of the fundamental understanding as well as their applications, ranging from biomedical to self‐healing smart ...materials. On the other hand, the reactions that occur in single‐crystal‐to‐single‐crystal (SCSC) fashion offer great details of the structure, geometry and stereochemistry of the product. However, SCSC 2+2 oligomerization is rather difficult and rare. Further, till date there are no reports for a reversible 2+2 oligomerization in SCSC fashion. In this work, four halogen‐substituted acrylic dienone molecules were deliberately designed and their ability to participate in 2+2 cycloaddition reaction in solid state was studied under visible light. Despite of having the required alignment of double bonds of dienes in all four crystal structures, they were found to exhibit variable reactivities given the differences in their weak intermolecular interactions such as halogen⋅⋅⋅halogen, halogen⋅⋅⋅π and C−H⋅⋅⋅O interactions. Notably, one of these materials exhibits reversible oligomerization in a SCSC manner.
The first single‐crystal‐to‐single‐crystal reversible 2+2 photo‐oligomerization of conjugated dienones under visible light is reported.
Abstract
Development of efficient and low cost electrocatalysts has been an important area of research in the field of materials chemistry. In this regard metal‐organic gels (MOGs) are one of the ...promising materials and they are being utilized for various materials applications including energy conversion and storage. Electrochemical applications of the MOGs are still in its infancy and further studies are required for exploration of structure‐property correlation that is crucial for targeted and efficient materials design. Herein we report multi stimuli responsive MOGs containing a tris‐tetrazole‐tri‐amido based organic ligand. The self‐assembly of the threefold symmetric ligand with Co(II)/Ni(II) acetates results in the MOGs with distinct morphological and structural characteristics, regardless of containing the same organic ligand. These MOGs were synthesized by direct mixing of the precursors under ambient conditions. The xerogels of these MOGs (
Co‐MOG′
and
Ni‐MOG′
) exhibit excellent OER performance as the
Co‐MOG′
and
Ni‐MOG′
shows the overpotential of 312 mV and 418 mV at 10 mA/cm
2
in an alkaline electrolyte. Electrocatalytic performance of the xerogels were correlated to their structural features like distinct morphology and porosity of the material that facilitates the mass transfer and maximum exposure to the electrochemical active sites. Importantly, this work demonstrates the functional application of MOGs as electrocatalysts for OER and the effect of metal ion, porosity and morphology on their overall performance.
Catalytic transformation of CO
into value-added chemical products can provide an appropriate solution for the raising environmental issues. To date, various metal-organic frameworks (MOFs) with ...transition metal ions have been explored for CO
capture and conversion, but alkaline earth metal-based MOFs are comparatively less studied. Metal ions like Sr(II) having relatively large radius give rise to a high coordination number resulting in higher stability of the MOFs. Moreover, the introduction of N-rich functional group in organic linker like -NH
, -CONH- and triazole into MOF backbone enhance their CO
capture and conversion efficiency. Herein, the effect of amine group on the catalytic efficiency of MOFs for CO
cycloaddition with epoxides under solvent free and ambient conditions are presented. The di-carboxylates, such as 5-aminoisophthalate (AmIP) and 5-bromoisophthalate (BrIP) were utilized to synthesize Sr(II) based MOFs. The Zn(II) MOF was synthesized using tetra-carboxylate containing amide spacer (OAT) and 4-amino-4H-1,2,4-triazole (AMT). All three MOFs exhibited porous networks with guest available volume ranging from 15 to 58 %. The catalytic efficiency of the MOFs towards carbon dioxide fixation reaction was explored. The catalytic performances revealed that the presence of amine group in the channels enhances the catalytic efficiency of the MOFs.
The synthesis of reversible oligomer/polymers is fascinating both from the perspective of the fundamental understanding as well as their applications, ranging from biomedical to self‐healing smart ...materials. On the other hand, the reactions that occur in single‐crystal‐to‐single‐crystal (SCSC) fashion offer great details of the structure, geometry and stereochemistry of the product. However, SCSC 2+2 oligomerization is rather difficult and rare. Further, till date there are no reports for a reversible 2+2 oligomerization in SCSC fashion. In this work, four halogen‐substituted acrylic dienone molecules were deliberately designed and their ability to participate in 2+2 cycloaddition reaction in solid state was studied under visible light. Despite of having the required alignment of double bonds of dienes in all four crystal structures, they were found to exhibit variable reactivities given the differences in their weak intermolecular interactions such as halogen⋅⋅⋅halogen, halogen⋅⋅⋅π and C−H⋅⋅⋅O interactions. Notably, one of these materials exhibits reversible oligomerization in a SCSC manner.
The first single‐crystal‐to‐single‐crystal reversible 2+2 photo‐oligomerization of conjugated dienones under visible light is reported.
