Rapid production of acid-functionalized infinite coordination polymer nanoparticles and their calcination to mineral metal oxide

Charge separation effect in the nanocomposites of Co3O4-QDs: visible light photocatalytic dye degradation in aqueous solutions

Photo-treatment of water is a promising environmentally friendly process that provides clean water and makes wastewater reusable in industry. Thus, efforts toward finding highly efficient photocatalysts have gained a huge attention to remove the organic contaminants in water. Quantum dots (QDs) are extensively utilized for photocatalytic remediation regarding their prominent optical, electrical, and chemical properties. Herein, we report the highly efficient and environmentally friendly synthesis of Co₃O₄-QDs-based graphene quantum dots (GQDs) and infinite coordination polymer comprising Zn nodes (Zn-ICP) nanocomposites as active and robust photocatalysts for photo-assisted water treatment. The pristine Co₃O₄-QDs, GQDs, and Zn-ICP showed lower activity under visible light. However, after functionalization of GQDs and Zn-ICP with Co₃O₄-QDs, the activity increased, and more photocatalytic efficiency was achieved. For instance, Zn-ICP, GQDs, Co₃O₄-QDs, Co₃O₄-QDs/Zn-ICP, and Co₃O₄-QDs/GQD degraded 21, 19, 52, 73, and 83% of rhodamine B (RhB) and 34, 46, 50, 73, and 76% of methylene blue (MB) after 60 min. The high photocatalytic efficiency was ascribed to the conjugation of Co₃O₄-QDs with GQDs and Zn-ICP which causes efficient absorption of visible light. The existence of Co₃O₄-QDs was found to be essential not only for effective charge separation but also widening the region of light absorption followed by increase in photocatalytic performances. Charge separation in photocatalytic reactions, energy levels of nanocomposites, and mechanism of the photocatalytic process were investigated by photoluminescence spectra (PL), Mott-Schottky, electrochemical impedance (EIS), and diffuse reflectance UV-Vis spectroscopy (DRS).

Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.

Designing a New Efficient Photocatalyst Based on Functionalization of Zn-Infinite Coordination Polymer with Ru(acac)3 Complex for Dye Degradation in Aqueous Solutions: Charge Separation Effect

A new Zn-containing infinite coordination polymer, Zn-ICP, functionalized with Ru(acac)₃ complex was designed and utilized as an efficient visible light photocatalyst for dye degradation in aqueous solutions. Incorporation of Ru(acac)₃ not only extended the light absorption of the Zn-ICP to the visible region but also led to electron-hole separation. Upon visible light illumination, photoinduced electron transfer from excited state of Zn-ICP to Ru(acac)₃ occurred, resulting in electron-hole separation as indicated by photoluminescence and electrochemical impedance spectroscopy. The obtained Ru-Zn-ICP revealed enhanced visible light photocatalytic activity in degradation of organic pollutants compared to pristine Zn-ICP owing to photoinduced electron transfer in the Ru-Zn-ICP system and efficient separation of photogenerated electron-hole pairs. The prepared Ru-Zn-ICP photocatalyst was readily recycled without major loss of activity in the successive cycles.

A new water-insoluble coordination polymer as efficient dye adsorbent and olefin epoxidation catalyst

A new water-insoluble bi-metallic coordination polymer was simply prepared via polymerization-precipitation of molybdenum complex building blocks with Zn²⁺ cation. The linker was a di-carboxylic acid consisting of two coordination sites i.e. N,O and COO^- suitable for coordinating to MoO₂ unit and Zn²⁺, respectively. Characterization of the prepared coordination polymer was carried out with various physicochemical methods which confirmed the proposed structure. The prepared coordination polymer preferentially adsorbed methylene blue (more than 92% of methylene blue after 2 min) relative to methyl orange and can be reused at least four times without any loss of adsorption efficiency. The adsorption process of both dyes followed the pseudo-second order kinetic equation. Additionally, the obtained coordination polymer catalyzed epoxidation of olefins with tert-butylhydroperoxide (TBHP) quantitatively with excellent selectivity (>99%) under mild reaction conditions.

Zinc-Containing Coordination Polymer as a Suitable Precursor for Solid State Synthesis of ZnO

Uniform zinc-containing infinite coordination polymer (ICP) nanoparticles were achieved via a straightforward and rapid precipitation method in 5min, from a bi-thioglycolate functionalized salpn ligand (salpn=N,N′-bis(salicylidene)-1,3-propanediamine) as linker and zinc acetate. Characterization of the resulting product was performed by CHN elemental analysis, inductively coupled plasma–optical emission spectroscopy, FT-IR spectroscopy, thermogravimetric analysis, electron microscopies (FE-SEM and HR-TEM), and photoluminescence spectroscopy. Elemental analyses verified the proposed structure for the ICP with a 1:2 ratio of the salpn type ligand and Zn2+ ion. FE-SEM, TEM, and AFM analyses unveiled the existence of nanoparticles with diameters of ~30nm. PL spectroscopy showed a blue shift in emission peak of the ICP with regards to the organic ligand. The obtained ICP was utilized as a precursor to synthesize ZnO nanoparticles with wurtzite structure. An increase in bandgap of the prepared ZnO nanoparticles was observed in comparison with bulk ZnO as a result of quantum confinement of photogenerated electron–hole pairs. This method can be exploited for the synthesis of other coordination polymer micro/nanostructures.

One-Pot Synthesis of Core–Shell Structured Metal–Organic Coordination Polymer Microspheres with a Hierarchical Microporous–Mesoporous–Macroporous Structure

New core–shell structured metal–organic coordination polymer (CP) microspheres with a hierarchical microporous–mesoporous–macroporous structure are synthesized by a one-pot template-free method. The ligand L with a Schiff-base functional group is obtained by reacting 3-hydroxy-4-aminobenzoic acid with para-benzaldehyde. The coordination polymer microspheres (Zn-L-CP) are obtained by mixing the ligand L and zinc nitrate hexahydrate together under hydrothermal conditions. The resultant coordination polymer microspheres with a core–shell structure are characterized by FT-IR and solid state NMR spectroscopy, transmission and scanning electron microscopy, and nitrogen adsorption–desorption measurements. The obtained Zn-L-CP microspheres are proved to be effective heterogeneous catalysts for the deacetylation reaction with the merits of easy recycling and stability. The yield is 96% when using methanol as solvent, and the yield can remain at 90% after seven cycles.

Rapid production of cadmium infinite coordination polymer nanofiber via solvent induced precipitation method

The precipitation synthesis of cadmium infinite coordination polymer (Cd-ICP) nanofibers with a high degree of uniformity is reported. The elemental analyses (CHN and ICP-OES), energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA) show that thermally robust monodisperse solid consists of bi-carboxylic acid linker and cadmium ion. The coordination between the Cd²⁺ ion and bi-carboxylic acid linker was investigated by Fourier transform infrared (FT-IR) spectroscopy. The photoluminescence (PL) properties of the Cd-ICP were studied in comparison with those of the bi-carboxylic acid linker. It was shown that the emission intensity of the Cd-ICP is much stronger than linker due to the structural rigidity after the coordination of linker to Cd ions. The field emission scanning electron microscopy (FE-SEM) results show that after calcination of the Cd-ICP the morphology changed from fiber to hexagonal-like disc. Furthermore, the results of UV-Vis spectroscopy show larger band gap for obtained CdO relative to the bulk counterpart.