Jingyan Xie

Hydroxyl-Exchanged Nanoporous Ionic Copolymer toward Low-Temperature Cycloaddition of Atmospheric Carbon Dioxide into Carbonates

An ionic copolymer catalyst with nanopores, large surface area, high ionic density, and superior basicity was prepared via the radical copolymerization of amino-functionalized ionic liquid bromide and divinylbenzene, followed with a hydroxyl exchange for removing bromonium. Evaluated in chemical fixation of CO2 with epoxides into cyclic carbonates in the absence of any solvent and basic additive, the nanoporous copolymer catalyst showed high and stable activity, superior to various control catalysts including the halogen-containing analogue. Further, high yields were obtained over a wide scope of substrates including aliphatic long carbon-chain alkyl epoxides and internal epoxide, even under atmospheric pressure and less than 100 °C for the majority of the substrates. On the basis of in situ Fourier transform infrared (FT-IR) investigation and density functional theory (DFT) calculation for the reaction intermediates, we proposed a possible reaction mechanism accounting for the superior catalytic activity of the ionic copolymer. The specifically prepared ionic copolymer material of this work features highly stable, noncorrosive, and sustainable catalysis and, thus, may be a new possibility for efficient chemical fixation of CO2 since it is an environmentally friendly, metal-free solid catalyst.

Pure-silica ZSM-22 zeolite rapidly synthesized by novel ionic liquid-directed dry-gel conversion

Shortening the crystallization process of zeolites is significant for their applications because of the energy savings. Here, we report a rapid synthetic route for pure-silica ZSM-22 zeolite with TON topology. The synthesis was achieved by dry-gel conversion, where the dry gel was prepared under an unusual acidic condition for hydrolyzing the silica precursor with 1,3-alkylimidazolium ionic liquid as the structure-directing agent (SDA). Highly crystallized pure-silica ZSM-22 can be synthesized within 2 days of crystallization, dramatically shorter than 10% of the conventional hydrothermal strategy. Using a similar procedure, Al-containing ZSM-22 can also be synthesized by simply adding aluminum salt in the initial gel. In addition, understanding of the structure-directing role of ionic liquids is attempted through characterizations of IR, TG, 1H and 13C NMR spectra.

One-Pot Template-Free Synthesis of Cu–MOR Zeolite toward Efficient Catalyst Support for Aerobic Oxidation of 5-Hydroxymethylfurfural under Ambient Pressure

Supported catalysts are widely studied, and exploring new promising supports is significant to access more applications. In this work, novel copper-containing MOR-type zeolites Cu-MOR were synthesized in a one-pot template-free route and served as efficient supports for vanadium oxide. In the heterogeneous oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) with molecular oxygen (O2) under ambient pressure, the obtained catalyst demonstrated high yield (91.5%) and good reusability. Even under the ambient air pressure, it gave a DFF yield of 72.1%. Structure-activity relationship analysis indicated that the strong interaction between the framework Cu species and the guest V sites accounted for the remarkable performance. This work reveals that the Cu-MOR zeolite uniquely acts as the robust support toward well-performed non-noble metal heterogeneous catalyst for biomass conversion.

Hydrophilic mesoporous poly(ionic liquid)-supported Au–Pd alloy nanoparticles towards aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid under mild conditions

Design of stable high-performance heterogeneous catalysts has become crucial for efficient catalytic conversion of renewable biomass into high value-added chemicals. Noble metal alloy nanoparticles (NPs) are of great interest due to their unique tunable structures and high activity. In this study, Au–Pd alloy NPs supported on hydrophilic mesoporous poly(ionic liquid) (MPIL) exhibited encouragingly high performance in the aerobic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) in water under mild conditions. Nearly complete conversion of HMF is attained at a low temperature of 90 °C under atmospheric O2, resulting in 99% FDCA yield and high turnover number (TON) of up to 350. After reaction, the catalyst can be facilely recovered and reused with stable activity. Surface wettability plays a dominant role in the oxidation of HMF to FDCA, and synergistic alloy effect accounts for high activity. The results also show that MPILs are a promising support platform to achieve stable and efficient metal NPs through task-specific design of functional monomers.

One-Pot Synthesis of Zeolitic Strong Solid Bases: A Family of Alkaline-Earth Metal-Containing Silicalite-1

Fabricating stable strong basic sites in well-preserved crystallized zeolitic frameworks still remains a difficult issue. Here, we reported a family of MFI-type metallosilicate zeolites, AeS-1 (Ae: alkaline-earth metal ions of Mg, Ca, Sr or Ba; S-1: silicalite-1) through a direct one-pot hydrothermal method involving the acidic co-hydrolysis/condensation of the silica precursor with the Ae salts. Step-by-step full characterizations were designed and conducted for in-depth discussion of the Ae status in AeS-1. Strong basicity (H_≈22.5-26.5) was detected in AeS-1. The basicity was further confirmed by CO2 sorption measurements, (13) C NMR spectra of chloroform-adsorbed samples, and (1) H→(13) C and (1) H→(29) Si cross-polarization magic-angle spinning NMR spectra of ethyl cyanoacetate-adsorbed samples. The results of Knoevenagel condensations demonstrated the excellent solid base catalysis of AeS-1, which showed high activity, reusability, and shape-selectivity, all of which are explained by Ae-derived zeolitic intracrystalline strong basic sites.

Morphology-controlled synthesis of large mordenite crystals

The morphology-controlled synthesis of mordenite (MOR) zeolites was achieved using the acidic hydrolysis route, which was started by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS), followed by switching the synthetic gel to basic conditions for hydrothermal crystallization. The synthesis by using tetraethylammonium hydroxide as the template resulted in a series of large MOR crystals with different morphologies, such as bulky sphere, circular pie, flat prism, hexagonal star-like prism and ellipsoid. Moreover, column, elongated spindle, short spindle, petal and circular pie shaped MOR crystals could be obtained without using an organic template in the above synthetic route. Among these morphologies, the bulky sphere, hexagonal star-like prism and petal shaped crystals were generated on MOR zeolites for the first time. The obtained products were characterized by XRD, SEM and N2 adsorption experiments. Various synthetic parameters were systematically investigated, including hydrolysis conditions for TEOS, molar composition of the initial gel, crystallization time and temperature. The results demonstrated that MOR zeolites can be synthesized through the acidic hydrolysis route, and their morphology can be facilely controlled through tuning the elemental synthetic conditions.

Mg2+-derived mesoporous ultra-high silica twelve-membered-ring basic zeolites: straightforward synthesis and catalytic performance

Mg2+-derived mesoporous ultra-high silica twelve-membered-ring zeolites with multiple topologies (MOR, BEA and MTW) were straightforwardly synthesized by a one-pot route, where the crucial step was the co-hydrolysis/condensation of silica source and magnesium salt under moderate acidic conditions. SiO2/Al2O3 ratios can be adjusted from ∼30 to as high as 410, thus generating superior basicity that was further improved by the incorporation of Mg species. A mesoporous structure was self-formed without the assistance of any template or special strategy. Catalysis tests showed high activity of these zeolites in a typical base reaction, Knoevenagel condensation, even for the bulky substrates due to the enhanced mass transfer arising from the mesopores. This methodology provides a promising approach towards target synthesis of valuable Mg2+-derived mesoporous ultra-high silica zeolites with tunable acid/base properties, which can even act as an efficient mesoporous zeolitic solid base.

Construction of Acid-Base Synergetic Sites on Mg-bearing BEA Zeolites Triggers the Unexpected Low-Temperature Alkylation of Phenol

Novel Mg‐bearing BEA zeolites are synthesized to simultaneously endow significantly enhanced basicity without compromising acidity over the zeolite framework. Serving as efficient solid acid–base bifunctional catalysts, they achieve the liquid‐phase selective methylation of phenol with methanol to produce o‐ and p‐cresol (o/p=2) under mild conditions. The method is readily extendable to the alkylation of phenols with various alcohols. Stereo‐ and regioselectivity (>95 % for p‐product) was attained on the alkylation of phenol with bulky tert‐butyl alcohol, rendering the first acid–base cooperative shape‐selective catalysis relying on the basicity of zeolites. A preliminary mechanistic analysis reveals that the remarkable activity and shape‐selectivity come from the superior special acidic–basic synergetic catalytic sites on the uniform microporous channels of the BEA zeolite.

Direct synthesis of V-containing all-silica beta-zeolite for efficient one-pot, one-step conversion of carbohydrates into 2,5-diformylfuran

Vanadium (V)-containing all-silica beta-zeolites (VSi-Beta) were directly synthesized using a dry-gel-conversion route, in which the gel was prepared from the acid-catalysed co-hydrolysis of a silica precursor and ammonium metavanadate. Besides the framework isolated V species, VSi-Beta contained tetrahedral [V2O7]4− and (VO3)nn− species that were bonded to the framework with a high dispersion. These V species resisted the over-oxidation of fructose and efficiently catalyzed the oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-diformylfuran (DFF). As a result, VSi-Beta demonstrated high activity in the one-pot and one-step conversion of fructose into DFF using atmospheric oxygen (O2) in the presence of sulfuric acid, affording a high yield of 86.3% and a maximum turnover number (TON) of 270. The catalyst can be easily recovered by filtration and exhibits good reusability. Various other carbohydrates (glucose, sucrose, inulin, raffinose, maltose and starch) were also effectively converted into DFF using VSi-Beta.