Tunability of Photovoltaic Functions via Halogen Substitution [(Ade)2 CdX4](X = Cl, Br): A Class of Three-Dimensional Organic-Inorganic Hybrid Materials

Two new three-dimensional organic-inorganic hybrid crystalline materials, [(Ade)2 CdCl4] (1) and [(Ade)2 CdBr4] (2), were obtained by the slow evaporation of adenine (Ade) and cadmium chloride in aqueous solution at room temperature with hydrochloric acid and hydrobromic acid used as halogen sources. The structural, thermal, optical, and electrical properties were characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, variable-temperature-variable-frequency dielectric constant analysis, and electrochemical tests. With increasing the substitution of Cl by Br, the composition of the material changed and the space group shifted from P-1 to P21/m, with a significant blue-shift in the fluorescence emission. Changing the temperature induced the deformation of the three-dimensional framework structure formed by hydrogen bonding interactions, leading to dielectric anomalies. Cyclic voltammetry tests showed the good reversibility of the electrolysis process. The structural diversity of the complexes was realized by modulating the halogen composition, and a new method for designing novel organic-inorganic hybrids with controllable photoelectric functionality was proposed.

A review on production of metal organic frameworks (MOF) for CO2 adsorption

The environment sustenance and preservation of global climate are known as the crucial issues of the world today. Currently, the crisis of global warming due to CO₂ emission has turned into a paramount concern. To address such a concern, diverse CO₂ capture and sequestration techniques (CCS) have been introduced so far. In line with this, Metal Organic Frameworks (MOFs) have been considered as the newest and most promising material for CO₂ adsorption and separation. Due to their outstanding properties, this new class of porous materials a have exhibited a conspicuous potential for gas separation technologies especially for CO₂ storage and separation. Thus, the present review paper is aimed to discuss the adsorption properties of CO₂ on the MOFs based on the adsorption mechanisms and the design of the MOF structures. In addition, the main challenge associated with using this prominent porous material has been mentioned.

Chemically-Controlled Stacking of Inorganic Subnets in Coordination Networks: Metal-Organic Magnetic Multilayers

Coordination networks (CNs), such as, for instance, metal-organic frameworks (MOFs), can turn into remarkable magnets, with various topologies of spin carriers and unique opportunities of cross-coupling to other functionalities. Alternatively, distinct inorganic subnetworks that are spatially segregated by organic ligands can lead to coexisting magnetic systems in a single bulk material. Here, we present a system of two CNs of general formula Mn(H₂O) _x(OOC-(C₆H₄) _y-COO). The compound with two water molecules and one aromatic ring ( x = 2; y = 1) has a single two-dimensional magnetic subnet, while the material with x = 1.5 and y = 2 shows, additionally, another type of magnetic layer. In analogy to magnetic multilayers that are deposited by physical methods, these materials can be regarded as metal-organic magnetic multilayers (MOMMs), where the stacking of different types of magnetic layers is controlled by the choice of an organic ligand during the chemical synthesis. This work further paves the way toward organic-inorganic nanostructures with functional magnetic properties.

Shedding Light on the Protonation States and Location of Protonated N Atoms of Adenine in Metal-Organic Frameworks

We report the syntheses and structures of five metal–organic frameworks (MOFs) based on transition metals (Ni^II, Cu^II, and Zn^II), adenine, and di-, tri-, and tetra-carboxylate ligands. Adenine, with multiple N donor sites, was found to coordinate to the metal centers in different binding modes including bidentate (through N7 and N9, or N3 and N9) and tridentate (through N3, N7, and N9). Systematic investigations of the protonation states of adenine in each MOF structure via X-ray photoelectron spectroscopy revealed that adenine can be selectively protonated through N1, N3, or N7. The positions of H atoms connected to the N atoms were found from the electron density maps, and further supported by the study of C–N–C bond angles compared to the literature reports. DFT calculations were performed to geometrically optimize and energetically assess the structures simulated with different protonation modes. The present study highlights the rich coordination chemistry of adenine and provides a method for the determination of its protonation states and the location of protonated N atoms of adenine within MOFs, a task that would be challenging in complicated adenine-based MOF structures.

The protonation states and positions of hydrogen atoms in five adenine-based metal−organic frameworks were revealed using geometrical studies based on single-crystal XRD data supported by XPS spectra and DFT calculations.

Silver-induced reconstruction of an adeninate-based metal-organic framework for encapsulation of luminescent adenine-stabilized silver clusters

Bright luminescent silver-adenine species were successfully stabilized in the pores of the MOF-69A (zinc biphenyldicarboxylate) metal-organic framework, starting from the intrinsically blue luminescent bio-MOF-1 (zinc adeninate 4,4'-biphenyldicarboxylate). Bio-MOF-1 is transformed to the MOF-69A framework by selectively leaching structural adenine linkers from the original framework using silver nitrate solutions in aqueous ethanol. Simultaneously, bright blue-green luminescent silver-adenine clusters are formed inside the pores of the recrystallized MOF-69A matrix in high local concentrations. The structural transition and concurrent changes in optical properties were characterized using a range of structural, physicochemical and spectroscopic techniques (steady-state and time-resolved luminescence, quantum yield determination, fluorescence microscopy). The presented results open new avenues for exploring the use of MOFs containing luminescent silver clusters for solid-state lighting and sensor applications.

Porous materials based on metal–nucleobase systems sustained by coordination bonds and base pairing interactions

Two approaches to metal–nucleobase porous materials: coordination bond sustained MOFs and hydrogen bond pairing based SMOFs.

A new luminescent Cd(ii)-MOF as a highly selective chemical probe for Fe3+ in aqueous solution with mixed metal ions

A new luminescent Cd(ii)-MOF has been prepared by solvothermal reaction. The luminescent properties were investigated in detail, showing a highly selective sensitivity for sensing Fe³⁺ in aqueous solution with mixed metal ions.