A stable and highly selective metalloporphyrin based framework for the catalytic oxidation of cyclohexene

Polyoxometalate-Based Metal-Organic Frameworks with Both Proton Acid and Multioxidative Active Sites: Highly Efficient Catalytic Synthesis of Quinazolinones

Quinazolinone derivatives are an important class of pharmaceutical and pesticide intermediates, which are generally synthesized starting with the condensation reaction between aldehydes and 2-aminobenzamide to obtain corresponding intermediates and then oxidized to obtain the products. Although some catalysts have been developed currently for the synthesis of quinazolinone derivatives, their catalytic efficiency is relatively low because only the oxidative catalytic sites of the catalyst have been focused on. Herein, we synthesized three new polyoxometalate-based metal-organic frameworks, [CuI4(4,4'-bipy)7(Hn-1PMo12-nVnO40)]·2H2O (n = 1-3), which were formed by coordinating a Cu(I)-bipy complex with different Keggin-type phosphomolybdic acids. An important feature of these compounds is that they possess proton and multioxidative active sites [Cu(I) center and V(V) center]; thus, we applied them to the catalytic synthesis of quinazolinone derivatives. The results indicate that compound 3 has an excellent catalytic activity. Based on density functional theory calculations, it is speculated that protons participate in the aldehyde amine condensation reaction, which changes the reaction pathway and reduces the activation energy from 55.1 to 31.4 kcal/mol, thereby increasing the reaction rate significantly. Interestingly, Raman spectra and electron paramagnetic resonance measurements indicate the presence of CuIIOO• and •O2- during the oxidative dehydrogenation process, which facilitates the rapid consumption of 2-phenyl-2,3-dihydroquinazolin-4(1H)-one intermediates, thereby promoting the chemical reaction to move toward the positive direction. Thanks to the synergistic effect of multicatalytic sites, compound 3 achieved highly efficient catalytic synthesis of quinazolinones with 99% yield in 1 h.

Use of porphyrin-containing polymers of intrinsic microporosity as selective photocatalysts for oxidative detoxification of chemical warfare agent simulant

Porphyrin-based polymers of intrinsic microporosity (PIMs) in photocatalytic degradation of a mustard-gas simulant (2-chloroethyl ethyl sulfide (2-CEES)) was demonstrated. Under blue-ultraviolet (UV) light-emitting diode (LED) irradiation, porphyrin-based PIMs PP-H2 and PP-Zn(II) worked as effective heterogeneous photocatalysts for oxidation of 2-CEES. Solvent played an important role in the conversion and selectivity of 2-CEES oxidation. When AcCN was used as a solvent, PP-H2and PP-Zn(II) demonstrated complete conversion of 2-CEES in 30 and 50 min, respectively, whereas they showed complete conversion at 60 and 70 min, respectively, when MeOH was used as a solvent. Moreover, these PIMs produced 2-chloroethyl ethyl sulfoxide (2-CEESO) as a major product with small amounts of 2-chloroethyl ethyl sulfone (2-CEESO[Formula: see text], ethyl methoxyethyl sulfoxide (EMSO), and vinyl sulfoxide (EVS) as side products in most solvents. However, when MeOH was used as a solvent, highly toxic 2-CEESO2 was not observed as a side product. Furthermore, these PIMs showed no significant changes in photocatalytic activity even after five cycles of reuse, indicating their high stability. Thus, the series of PIMs prepared herein can perform well as heterogeneous catalysts in photooxidation of 2-CEES under blue-UV LED light, with PP-H2 being the most effective oxidation catalyst, leading to fast conversion and high selectivity.

Photoresponsive frameworks: energy transfer in the spotlight

In this paper, spiropyran-containing metal- and covalent-organic frameworks (MOFs and COFs, respectively) are probed as platforms for fostering photochromic behavior in solid-state materials, while simultaneously promoting directional energy transfer (ET). In particular, Förster resonance energy transfer (FRET) between spiropyran and porphyrin derivatives integrated as linkers in the framework matrix is discussed. The photochromic spiropyran derivatives allow for control over material optoelectronic properties through alternation of excitation wavelengths. Photoinduced changes in the material electronic profile have also been probed through conductivity measurements. Time-resolved photoluminescence studies were employed to evaluate the effect of photochromic linkers on material photophysics. Furthermore, "forward" and "reverse" FRET processes occurring between two distinct chromophores were modeled, and the Förster critical radii and ET rates were estimated to support the experimentally observed changes in material photoluminescence.

Selective cyclohexene oxidation to allylic compounds over a Cu-triazole framework via homolytic activation of hydrogen peroxide

Utilization of metal-organic frameworks as heterogeneous catalysts is crucial owing to their abundant catalytic sites and well-defined porous structures. Highly robust [Cu3(trz)3(μ3-OH)(OH)2(H2O)4]·2H2O (trz = 1,2,4-triazole) was employed as a catalyst for liquid-phase cyclohexene oxidation with hydrogen peroxide (H2O2). Possessing the porous structure together with Lewis acid attributes from the triangular [Cu3(trz)3(μ3-OH)] center, selective oxidation of cyclohexene to allylic products gives a molar yield of 31% with 87% selectivity. According to the highly selective allylic production, the reaction over the present Cu-MOF plausibly occurs via homolytic activation of H2O2. This finding elucidates the unique features of the MOF for efficient catalysis of cyclohexene oxidation.