Controllable Synthesis, Characterization, and Catalytic Properties of Three Inorganic–Organic Hybrid Copper Vanadates in the Highly Selective Oxidation of Sulfides and Alcohols

Abstract

Three novel inorganic−organic hybrid copper vanadates α- and [Cu(mIM) 2 )](VO 3 ) 2 (3) (mIM = 1-methylimidazole) have been synthesized by rationally controlling of the hydrothermal conditions and fully characterized by singlecrystal XRD, powder XRD, elemental analyses, TGA, and FT-IR spectroscopy. Interestingly, compounds 1 and 2 were isolated as geometric isomers by tuning the solvothermal reaction temperature. Because of the different coordination modes between the tetradentate [V 4 O 12 ] 4− and [Cu(mIM) 4 ] 2+ subunits, the supramolecular structures of the two isomers show a 3D framework with an interpenetrating diamond topology for 1 and a 2D network for 2, respectively. Compound 3 was obtained by tuning the reaction temperature and the ratio of mIM/H 2 O, which showed interesting left-and right-handed helixes with an identical pitch of ca. 5.388 Å in its 2D network structure. As heterogeneous catalysts, compounds 1−3 exhibit excellent catalytic performance in the oxidation of sulfides with H 2 O 2 as oxidant. Among them, the catalytic activity of 1 (conv. up to 98.7%, sele. up to 100%) outperforms others and can be reused without losing its activity. The activity of 1 is also investigated in the oxidation of various alcohols, and excellent results (conv. up to 98.5%, sele. up to 100%) are obtained.

In Situ Ligand-Transformation-Involved Synthesis of Inorganic–Organic Hybrid Polyoxovanadates as Efficient Heterogeneous Catalysts for the Selective Oxidation of Sulfides

“…The selectivity was further promoted to 98% along with a reduction in the reaction temperature to 50 °C; nevertheless, the conversion is only 83% (entry 2). Subsequently, when the dosage of TBHP was increased to 0.75 mmol, the conversion and selectivity of 100% and 99% were gratifying (entry 4), until the dosage of 1 mmol resulted in a declining selectivity of 84% (entry 7), which is superior to the previously reported POV-based inorganic–organic hybrids, such as [Cu­(mIM) 4 ]­V 2 O, [Co 2 ­L 0.5 ­V 4 ­O 12 ]·3DMF·5H 2 O, [(C 2 ­N 2 ­H 8 ) 4 ­(CH 3 O) 4 ­V IV 4 ­V V 4 ­O 16 ]·4CH 3 OH, K 6 ­H­[V V 17 ­V IV 12 ­(OH) 4 ­O 60 ­(OOC­(CH 2 ) 4 ­COO) 8 ]· n H 2 O, and so on but comparable to the aforementioned example (en)­[Cu 3 (ptz) 4 (H 2 O) 4 ]­[Co 2 Mo 10 H 4 O 38 ]·24H 2 O . Following continual attempts to enhance the selectivity in the oxidation of MPS to sulfoxide by tuning the above factors, including the dosage of the catalyst (entry 6), reaction time (entries 8 and 9), solvent types (ethanol, trichloromethane, and acetonitrile; entries 12–14), no more satisfying results were obtained.…”

Two Polymorphic Polyoxometalate-Based Metal–Organic Frameworks for the Efficient Synthesis of Functionalized Sulfoxides and Detoxification of Mustard Gas Simulants

“…Taking these into account, the rational design and synthesis of crystalline POM-based MOFs (POMOFs), which can achieve the good dispersion of POMs at the molecular level and expose more accessible active sites, have been developed as an efficient strategy for optimizing and stabilizing traditional POM fragments. Meanwhile, the ordered porous structures in POMOFs facilitate the accessibility of substrate molecules to active POM fragments, actualizing the maximum benefit of POMs and the homogeneity of the heterogeneous catalysis. − Many pioneering works by Liu, Hill, Hu, Su, Farha, Lan, and other groups have demonstrated that crystalline POMOFs as heterogeneous catalysts exhibit excellent catalytic performance and recoverability in alcohol oxidation, phenol oxidation, epoxidation, and CO 2 reduction. − By comparison, only a few POMOF crystalline materials were successfully applied to the oxidation reaction of sulfides until now. For instance, several polyoxovanadate-based MOFs, [Co 2 L 0.5 V 4 O 12 ]·3DMF·5H 2 O, [Co­(HDTBA)­V 2 O 6 ], [Ni 2 (1-vIM) 7 H 2 O]­[V 4 O 12 ]·H 2 O, and [Cu­(mIM) 4 ]­V 2 O 6 , were successively manufactured and efficaciously catalyzed the H 2 O 2 - or TBHP-based oxidation of sulfides and oxidative detoxification of the sulfur mustard simulant (2-chloroethyl ethyl sulfide, CEES). ,− Yang et al successfully prepared a porous POMOF built by amino-modified Anderson-type POM and 4-connected tetrahedral tetrakis­(4-formylphenyl)­silicon, which exhibits a high-efficiency catalytic activity in the oxidation of sulfides using H 2 O 2 as a green oxidant .…”

Heterogenized ionic liquid-metal oxide hybrids: enhanced catalytic activity in the liquid-phase Beckmann rearrangement

“…Catalytic reactions that have benefited from this approach include transesterification, 2 Knoevenagel condensation, 3 Sonogashira coupling, 4 the synthesis of cyclic carbonates from CO2 and epoxide, 5 asymmetric epoxidation, 6 hydrogenation, 7 ethylene polymerization, 8 dehydration, 9 and the selective oxidation of sulfides and alcohols. 10 However, whilst catalytically efficient, the instability of many of these hybrid materials limits their widespread application.…”

“…The synergistic effect of both inorganic and organic moieties in these hybrid materials leads to remarkable improvements in catalytic performance in many applications, including acid–base catalysis, chiral transformations, polymerization, and selective oxidation. Catalytic reactions that have benefited from this approach include transesterification, Knoevenagel condensation, Sonogashira coupling, synthesis of cyclic carbonates from CO 2 and epoxide, asymmetric epoxidation, hydrogenation, ethylene polymerization, dehydration, and selective oxidation of sulfides and alcohols . However, while catalytically efficient, the instability of many of these hybrid materials limits their widespread application.…”