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.

A recirculating device of cooling water powered by solar energy for the laboratory.

Aimed at energy conservation and water saving for the lab, we have designed and constructed one kind of lab-scale small recirculating device of cooling water utilizing a water recirculator coupled to a solar energy system via a self-made multifunctional voltage regulator, which is equipped with an active heat radiator and powered by a solar energy system. It can provide cooling water for 1-3 sets of ordinary refluxing setups in series without additional consumption of water and electricity. The temperature difference between the water in the bucket and the environment is less than 4 °C for eight common solvents in single refluxing set-up or three combined refluxing setups with different solvents in series. In the performance assessment experiments for the refluxing of eight common solvents with different boiling point, the largest solvent loss is less than 6% if the condenser is open to the air in the refluxing time of 8 h, but none obvious solvent loss are found if the condensers were equipped with an oil bubbler. Control experiments indicates that the preparation of bromoethane/ethyl acetate/propyl hexanoate using our water recirculator can achieve almost unanimous yields in relative to those reactions using tap water as cooling water.

Exploring Electron Transfer Mechanism in Synergistic Interactional Reduced Polyoxometalate-Based Cu(I)-Organic Framework for Photocatalytic Removal of U(VI).

Photocatalytic reduction of U(VI) is a promising method for removing uranium containing pollutants. However, using polyoxometalate-based metal-organic frameworks (POMOFs) for photoreduction of U(VI) is rare, and the relevant charge transfer pathway is also not yet clear. In this article, we demonstrate a highly efficient strategy and revealed a clearly electron transfer pathway for the photoreduction of U(VI) with 99% removal efficiency by using a novel POMOF, [Cu(4,4'-bipy)]5·{AsMo4VMo6VIV2VO40(VIVO)[VIVO(H2O)]}·2H2O (1), as catalyst. The POMOF catalyst was constructed by the connection of reduced {AsMo10V4} clusters and Cu(I)-MOF chains through Cu-O coordination bonds, which exhibits a broader and stronger light absorption capacity due to the presence of reduced {AsMo10V4} clusters. Significantly, the transition of electrons from Cu(I)-MOF to {AsMo10V4} clusters (Cu → Mo/V) greatly inhibits the recombination of photogenerated carriers, thereby advancing electron transfer. More importantly, the {AsMo10V4} clusters are not only adsorption sites but also catalytically active sites. This causes the fast transfer of photogenerated electrons from Mo/V to UO22+(Mo/V → O → U) via the surface oxygen atoms. The shorter electron transmission distance between catalytic active sites and UO22+ achieves faster and more effective electron transport. All in all, the highly effective photocatalytic removal of U(VI) using the POMOF as a catalyst is predominantly due to the synergistic interaction between Cu(I)-MOFs and reduced {AsMo10V4} clusters.

Effective oxygen activation on polyoxometalate-based hybrids for epoxidation of alkenes.

Two polyoxometalate-based hybrids, [M(btap)3(H2O)3(HPW12O40)]·xH2O (M-PW, M = Co/Mn, btap = 3,5-bis(1',2',4'-triazol-1'-yl)pyridine) were synthesized. Co-PW exhibited higher activity and selectivity towards olefin epoxidation than Mn-PW due to the synergistic effect between CoII and PW, in which the Co centers activate O2 to ˙O2- and further binding of free H+ from PW affords the active peroxyacid.

Rapid Oxidative Detoxification of Mustard Simulant by the Multisite Synergistic Catalytic Action of {PMoVI11MoVO40CuI8} Units.

Under hydrothermal and solvent-thermal conditions, we synthesized two novel polyoxometalate (POM)-based hybrids: [CuI4(Pz)2(H2O)8(PMoVI11MoVO40)]·3.5H2O (1, Pz = pyrazine) and [(C2H8N)5(HPMoVI9MoV3O40)]·DMF·4H2O (2). Single-crystal X-ray diffraction indicates that compound 1 is a three-dimensional structure consisting of Cu (I), {PMo12} anions, Pz, and water, where Cu (I) can be considered as Lewis acid sites. Furthermore, both compounds 1 and 2 possess favorable catalysis activity in catalyzing the conversion of chemical warfare agent simulant 2-chloroethylethyl sulfide (CEES) to nontoxic production of 2-chloroethylethyl sulfoxide (CEESO) under ambient temperature. Significantly, 1 could realize 98% conversion and 100% selectivity of CEES owing to the multisite synergy in the {PMoVI11MoVO40CuI8} units in which the tricoordinated Cu (I) could interact with S and O atoms from CEES and H2O2, respectively. This interaction not only decreases the distance of CEES from peroxomolybdenum species formed by H2O2 but also activates CEES.