Selective Synthesis Of Carbonyl Compounds Catalyzed By Oxovanadium Clusters And Zn(Cu)-MOFs

Carbonyl compounds are a kind of important organic matter in organic chemistry andthe conversion of cheap accessible alcohols, benzyl hydrocarbons and CO2in nature tocarbonyl compounds is one of very important organic conversion reactions. How to controlthe reaction to obtain only aldehydes or cyclic carbonates has become a hot research fieldof catalysis, and it has aroused widespread concern of chemists.This paper mainly focus on the selective conversion of alcohols, benzyl hydrocarbonsand carbon dioxide molecules to carbonyl compounds catalyzed by oxovanadium clustersor Zn(Cu)-MOFs (the oxovanadium cluster involved in this thesis were V6On(RIM)8,Pd-PMoVs and Pd-V-PMo12O40; Zn(Cu)-MOFs were Zn-BTC MOFs andHKUST-1@Fe3O4). The main work is as follows:(1) Imidazole functionalized polyoxovanadium clusters, that is V6O15(mIM)8(1),V6O14(mIM)8(2), V6O14(eIM)8(3)(mIM:1-Methylimidazole, eIM:1-Ethylimidazole),were firstly studied for activating alcohol molecules. These materials are chemically andstructurally stable, yet have the long-sought-after characteristic as highly efficient andselective catalysts for oxidation of various alcohols using molecular oxygen as the oxidant.Specifically, under un-optimized condition(acetonitrile as solvent,2atm O2pressure),compound3exhibits extraordinary efficiency in converting salicylol to salicylaldehydewith100%con. and high selectivity (96.7%). And indeed,3outperforms allvanadium-based catalysts tested under the same reaction conditions and even rivals somenoble-metal-based catalysts performed under higher pressure. Compound3further showshigh catalytic activities for the selective aerobic oxidation of aromatic alcohols, aliphaticalcohol (Conv.41.3-100%, Sele.92.4-96.7%). Furthermore, the polyoxovanadium cluster3can be readily recycled and reused with unchanged catalytic activity. A plausible catalyticcycle is also proposed.(2) In our previous work, three novel imidazole-functionalized hexanuclearoxidavanadium catalysts have exhibited excellent selectivity in the aerobic oxidation ofalcohols under2atm pressure, and the conversion is yet to be improved. Three novel binary Pd-polyoxometalates [Pd(dpa)2]3[PW12O40]2·12DMSO (2);[Pd(dpa)2]3[PMo12O40]2·12DM-SO·2H2O (3);[Pd(dpa)(DMSO)2]2[HPMo10V2O40]·4DMSO (4) and Pd(dpa)(OAc)2·2H2O(1) were studied for activating C-H bonds in benzyl alcohol. It is found that compound4ismore active than the other three compounds in the selective aerobic oxidation of alcohols atambient pressure. Interestingly, during the catalytic recycle of compound4, the reactiontime of the second, third or fourth cycle is shorter than the first round. An unprecedentedternary Pd-V-polyoxometalates [Pd(dpa)2(VO(DMSO)5)2][PMo12O40]2·4DMSO (5) hasbeen captured and characterized by single crystal X-ray diffraction through carefulexperiments, which is further proved to be the real active species and shows high catalyticactivities for the selective aerobic oxidation of aromatic alcohols (Conv.98.1-99.8%, Sele.91.5-99.1%). Moreover, based on control experiments, EPR and UV-vis spectra, a plausiblereaction mechanism for the oxidation of alcohols catalyzed by5was proposed.(3) Transformation and utilization of resources of carbon dioxide is one of theimportant subject of common concern in the world, synthesis of cyclic carbonates fromcarbon dioxide is one of the important route. Thus, developing more active componentsimple and environmentally friendly catalysts is one of the highlights. Three zinc-trimesicacid (Zn-BTC) MOFs, BIT-101, BIT-102and BIT-103, have been used in the coversion ofcarbon dioxide. Interestingly, BIT-103exhibit extraordinary catalytic performance (up toConv.100%and Sele.95.2%) in the cycloaddition of CO2under solvent-and halogen-freeconditions without any additives or co-catalysts. BIT-103is further used in the catalyticconversion of other epoxy compounds and shows high catalytic activities (Conv.96.6-100%, Sele.90.8-98.6%). Furthermore, these new MOFs can be fully recycled andreused without losing their activity.(4) In view of C-H bonds activation of benzyl hydrocarbon and C=O bond generation,under the condition of t-BuOOH as oxidant, HKUST-1@Fe3O4shows exceptional catalyticactivity for the oxidation of benzylic C–H bonds of diphenyl methane, xanthene andfluorine with up to99%conv.99%sel.. Importantly these MOF nanocomposites can beeasily recovered by simple magnetic separation and reused without losing any activitythrough multiple reaction cycles. This may serve as a start in designing MOF catalysts for continuous magnetic fluid bed.