Rational Assembly of Three-component Coordination Polymers as Heterogeneous Catalysts for CO2 Cycloaddition and Cyanosilylation Reactions.

Four new coordination polymers based on 5-(((1H-imidazol-2-yl)methyl)amino) isophthalic acid (H3L) and auxiliary ligands (1,10-phenanthroline, 2,2'-bipyridine, and 4,4'-bipyridine), namely, {[Zn(HL)(phen)(H2O)]·2H2O}n (CP 1), {[Ni(HL)(phen)(H2O)]}n (CP 2), {[Ni(HL)(2,2'-bpy)(H2O)]·2H2O}n (CP 3) and {[Cd(HL)(4,4'-bpy)0.5(H2O)]·2H2O}n (CP 4) were rationally assembled. Furthermore, these four CPs were screened as heterogeneous catalysts for CO2 cycloaddition and cyanosilylation reactions under mild conditions. The catalytic experiments showed that CP 1 had the better catalytic performance, excellent substrate tolerance and recyclability for the above two reactions. It is speculated that the excellent activity of CP 1 may be due to the open Lewis base site and the Lewis acidic characteristics of the zinc (II) center. After five cycles, the catalytic activities of CP 1 did not significantly decrease, and the structures remained unchanged. Therefore, the CP 1 was considered efficient and stable heterogeneous catalysts for above the two reactions.

Two 2D Metal-Organic Frameworks Based on Purine Carboxylic Acid Ligands for Photocatalytic Oxidation of Sulfides and CO2 Chemical Fixation.

Two two-dimensional (2D) layered metal-organic frameworks (MOFs), namely, {[Yb(L)(H2O)2NO3]·2H2O}n (Yb-MOF) and [Er(L)(H2O)3Cl]n (Er-MOF) (H2L = 5-((6H-purin-6-yl)amino)isophthalic acid), were constructed by a solvothermal method and characterized. The catalytic performance study showed that the Yb-MOF could efficiently catalyze the oxidation of sulfides to sulfoxides under 15 W light-emitting diode (LED) blue light irradiation. Electron paramagnetic resonance spectroscopy and free-radical trapping experiments demonstrated that the photocatalytic reaction process involved •O2-, and the corresponding mechanism was proposed. Moreover, Er-MOF exhibited good catalytic efficiency and excellent substrate tolerance in the cycloaddition reaction of CO2, and the reaction conditions were mild. After 5 cycles, the catalytic activities of two MOFs did not significantly decrease, and the framework structures remained unchanged. Therefore, the Yb-MOF and Er-MOF were considered efficient and stable heterogeneous catalysts.

Assembly of Functional Co(II) Metal-Organic Frameworks through a Mixed Ligand Strategy: Structure and Photocatalytic Degradation Properties.

Four Co(II)-based metal-organic frameworks (MOFs) were constructed by a mixed ligand strategy under solvothermal conditions. The controllable modification of the bridging groups in the secondary building units was realized by changing the anions in MOFs 1-3. The MOF 4 with 3D framework structure was obtained by regulating the solvent ratio following the synthesis process of MOF 3. Furthermore, the MOFs 1-4 exhibited efficient photocatalytic activity for the degradation of malachite green (MG) dye without any photosensitizer or cocatalyst under a low-energy light source, the decolorization ratio of MG all reached more than 96.0% within 60 min, and maximal degradation was obtained to be 99.4% (MOF 4). The recycling experiments showed that the degradation rate of MG was still higher than 91% after 10 cycles. In the MOF 4 as representation, the photocatalytic process was explored systematically. The possible mechanism of catalytic degradation was discussed, which proved the existence of efficient oxidation active factors (•O2-, •OH, and h+). The possible intermediates and degradation pathways were investigated based on high-performance liquid chromatography tandem mass spectrometry. Additionally, MOFs 1-4 also exhibited excellent photocatalytic activity for the degradation of methylene blue, methyl violet, rhodamine B, and basic red 9.

Effective detection of Ag+, Hg2+ and dye adsorption properties studies of Ln-MOFs based on a benzimidazole carboxylic acid ligand.

Five new lanthanide metal-organic frameworks (Ln-MOFs), namely {[Ln(L)]·Cl}n, [Ln = Pr(1), Nd(2), Eu(3), Ho(4), Ce(5)], based on a benzimidazole carboxylic acid ligand [H2L = 2-(2-carboxyphenyl)-1H-benzo[d]imidazole-6-carboxylic acid] were synthesized by a solvothermal method. Ln-MOFs 1-5 have the same two-dimensional layered structures. Interestingly, 1-5 exhibit excellent adsorption performance to anionic dye Congo red (CR), with adsorption capacities of 2724 mg g-1, 2719 mg g-1, 2718 mg g-1, 327 mg g-1, and 2273 mg g-1, respectively. Adsorption kinetics experiments showed that this kind of adsorption belonged to chemisorption; the hydrogen bonding and π-π interactions between the 1-5 host and CR guest molecules resulted in a high adsorption capacity. Luminescence and sensing experiments showed that 5 can be considered a promising multifunctional fluorescent sensor with good reusability and a high sensitivity toward Ag+ and Hg2+ ions, with detection limits of 1.7 × 10-7 and 2.5 × 10-6 M, respectively.