Mixed solvothermal synthesis and X-ray characterization of a layered copper coordination polymer, Cu(H2O)(1,3-BDC)·H2O (BDC=benzenedicarboxylate)

Chromium(II)-isophthalate 2D MOF with Redox-Tailorable Gas Adsorption Selectivity

Redox-active metal-organic frameworks (MOFs) are very promising materials due to their potential capabilities for postsynthetic modification aimed at tailoring their application properties. However, the research field related to redox-active MOFs is still relatively underdeveloped, which limits their practical application. We investigated the self-assembly process of Cr(II) ions and isophthalate (m-bdc) linkers, which have been previously demonstrated to yield 0D metal-organic polyhedra. However, using the diffusion-controlled synthetic approach, we demonstrate the selective preparation of a 2D-layered Cr(II)-based MOF material [Cr(m-bdc)]·H2O (1·H2O). Remarkably, the controlled oxidation of the developed 2D MOF using nitric oxide or dry oxygen resulted in modified porous materials with excellent H2/N2 adsorption selectivities.

Unpaired Electron-Induced Wide-Range Light Absorption within Zn (or Cu) MOFs Containing Electron-Withdrawing Ligands: A Theoretical and Experimental Study

In photocatalysis, it is of general interest to understand and design wide-range light-absorbing inorganic/organic hybrid materials with an excellent photo-induced intramolecular charge-transfer (ICT) effect. To verify the role of unpaired electrons in enhancing ICT within electron-withdrawing ligand-based metal-organic frameworks (MOFs), the molecular structure, density of states (DOS), and electronic structure of strong electron-deficient pyridine-diketopyrrolopyrrole (P-DPP)-based Zn (or Cu) MOFs were calculated in Gaussian package to validate the unpaired electron ICT. The electron spin resonance technique has detected the unpaired electrons for the coordination systems containing Zn-O or Cu-O clusters and P-DPP ligand on photoexcitation. The estimated band gaps from the DOS calculation for P-DPP-Cu and P-DPP-Zn are 1.4 and 2.4 eV, respectively, showing a good agreement with the experimental UV-vis optical spectra. The partial DOS, dipole moment, and frontier orbital analysis prove that the ICT should happen from Zn-O or Cu-O clusters to P-DPP ligands. This research may contribute to a comprehensive understanding of electron-withdrawing ligand-induced ICT within MOFs and shed light on the design of light-absorbing MOFs with excellent ICT or conductivity.

Framework disorder and its effect on selective hysteretic sorption of a T-shaped azole-based metal-organic framework

Metal-organic frameworks with highly ordered porosity have been studied extensively. In this paper, the effect of framework (pore) disorder on the gas sorption of azole-based isoreticular Cu(II) MOFs with rtl topology and characteristic 1D tubular pore channels is investigated for the first time. In contrast to other isoreticular rtl metal-organic frameworks, the Cu(II) metal-organic framework based on 5-(1H-imidazol-1-yl)isophthalate acid has a crystallographically identifiable disordered framework without open N-donor sites. The framework provides a unique example for investigating the effect of pore disorder on gas sorption that can be systematically evaluated. It exhibits remarkable temperature-dependent hysteretic CO2 sorption up to room temperature, and shows selectivity of CO2 over H2, CH4 and N2 at ambient temperature. The unique property of the framework is its disordered structure featuring distorted 1D tubular channels and DMF-guest-remediated defects. The results imply that structural disorder (defects) may play an important role in the modification of the performance of the material.

Supramolecular metallogels constructed from carboxylate gelators

Serendipity still plays a role in gel discovery as the prediction of gel formation is difficult. This work explores the role of ligand, metal salt, solvent, and temperature in the formation of a low molecular mass carboxylate iron(iii) system. The influence of each component is discussed. The gels obtained were characterised using thermal analysis, Fourier transform-infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, elemental analysis, microwave plasma-atomic emission spectroscopy, and inductively coupled plasma optical emission spectrometry. The response to external stimuli, including dye and gas sorption was examined.

Metal Complexes of Maleimide Compounds

The metal complexation ability of some N-substituted maleimides containing a carboxyl group was investigated. Thus, N-(4-carboxy-phenyl)-maleimide, N-(3-acetoxy-4-carboxy-phenyl)-maleimide and poly[ N-(3-acetoxy-4-carboxy-phenyl)-maleimide] were prepared and complexed with several transition metals, such as Co2+, Ni2+ and Cu2+. The formation of complexes which separated as precipitates from the reaction mixtures was confirmed by elemental and spectral analyses. The thermal stability of the complexes was evaluated by thermogravimetry.

Cu(i)Cu(ii)BTC, a microporous mixed-valence MOF via reduction of HKUST-1

A microporous mixed-valence Cu(i,ii)–BTC MOF is produced and exhibits two crystalline environments, bi-modal micropores, and superior water stability.