Hydrogen bond donor functionalized poly(ionic liquids)@MIL-101 for the CO2 capture and improving the catalytic CO2 conversion with epoxide

MIL-101(Cr)/aminoclay nanocomposites for conversion of CO2 into cyclic carbonates

We present the use of an amine functionalized two-dimensional clay i.e., aminoclay (AC), in the chemistry of a three-dimensional metal-organic framework (MOF) i.e., MIL-101(Cr), to prepare MIL-101(Cr)/AC composites, which are exploited as catalysts for efficient conversion of CO2 gas into cyclic carbonates under ambient reaction conditions. Three different MOF nanocomposites, denoted as MIL-101(Cr)/AC-1, MIL-101(Cr)/AC-2, and MIL-101(Cr)/AC-3, were synthesized by an in situ process by adding different amounts of AC to the precursor solutions of the MIL-101(Cr). The composites were characterized by various techniques such as FT-IR, PXRD, FESEM, EDX, TGA, N2 adsorption, as well as CO2 and NH3-TPD measurements. The composites were exploited as heterogeneous catalysts for CO2 cycloaddition reactions with different epoxides and the catalytic activity was investigated at atmospheric pressure under solvent-free conditions. Among all the materials, MIL-101(Cr)/AC-2 shows the best catalytic efficiency under the optimized conditions and exhibits enhanced efficacy compared to various MIL-101(Cr)-based MOF catalysts, which typically need either high temperature and pressure or a longer reaction time or a combination of all the parameters. The present protocol using MIL-101(Cr)/AC-2 as the heterogeneous catalyst gives 99.9% conversion for all the substrates into the products at atmospheric pressure.

Bimetallic MnZn-MOF-74 with enhanced percentage of MnIII: Efficiently catalytic activity for direct oxidative carboxylation of olefins to cyclic carbonates under mild and solvent-free condition

Multi-functional MOF catalyst with oxidative- and acid- centers showed potential in olefins oxidative carboxylation to cyclic carbonates directly. In this work, a series of bimetallic MnZn-MOF-74 with different molar ratios of Mn and Zn were synthesized successfully through a one-pot facile method. Thoroughly characterization indicated that the existence of Zn regulated the valance state distribution of Mn in the obtained MnZn-MOF-74. Mn99.3Zn0.7-MOF-74 with the highest ratio of MnIII (61.3 %) performed the most efficient activity for olefin direct tandem oxidative carboxylation reaction using aqueous tert-butyl hydroperoxide oxidant under solvent-free condition of 90 °C, 1.0 MPa CO2 and 4 h. Mn99.3Zn0.7-MOF-74 also showed satisfactory versatility and recyclability. Based on the experiments, a feasible mechanism was presented. Thanks to the high ratio of active MnIII as main oxidative center, the coordination unsaturated bimetal Mn and Zn as Lewis-acid sites, O2- of metal - O as Lewis-base sites and combined effect with Bu4NBr cocatalyst, Mn99.3Zn0.7-MOF-74 presented efficient performance for the direct synthesis of cyclic carbonates from olefins. The metal Zn in MOF can regulate the valance state distribution of Mn and result in efficient catalytic property, presenting a potential avenue for direct oxidative carboxylation reaction of olefins to cyclic carbonates synthesis.

Enhanced CO2 conversion through confinement of cross-linked ionic polymer within the pores of porous carbon materials

It is crucial to employ an integrated catalyst to avoid the complications of the recovery process. This work reports the fabrication of porous carbon@ionic liquid (PC@IL) composites with readily accessible active ion sites, achieved by confining cross-linked ionic liquid (IL) within the channels of porous carbon (PC). The incorporation of porous carbon not only confines the IL within its framework, creating microsites for CO2 adsorption and conversion, but also simplifies catalyst recovery. The results indicate that PC@IL composites exhibit excellent cycloaddition activity towards CO2 in a co-catalyst- and solvent-free environment. Notably, PC@IL(C)-24 demonstrates remarkable catalytic performance across various epoxides under 1 bar of CO2, with yields above 90 % at 90 °C for 12 h, and achieving a remarkable styrene carbonate yield of up to 92.8 % under a CO2 pressure of 1 bar (at 100 °C for 12 h). Control experiments confirm that the confinement effect exerted by N,S co-doped carbon on cross-linked IL plays a pivotal role in enhancing both stability and activity of PC@IL composites, thereby providing novel insights for designing functionalized porous carbon catalysts for CO2 cycloaddition conversion.

Treatment and Resource Utilization of Gaseous Pollutants in Functionalized Ionic Liquids

With the rapid development of science, technology, and the economy of human society, the emission problem of gas pollutants is becoming more and more serious, which brings great pressure to the global ecological environment. At the same time, the natural resources that can be exploited and utilized on Earth are also showing a trend of exhaustion. As an innovative and environmentally friendly material, functionalized ionic liquids (FILs) have shown great application potential in the capture, separation, and resource utilization of gaseous pollutants. In this paper, the synthesis and characterization methods of FILs are introduced, and the application of FILs in the treatment and recycling of gaseous pollutants is discussed. The future development of FILs in this field is also anticipated, which will provide new ideas and methods for the treatment and recycling of gaseous pollutants and promote the process of environmental protection and sustainable development.

Poly(ionic liquid)-coated hydroxy-functionalized carbon nanotube nanoarchitectures with boosted catalytic performance for carbon dioxide cycloaddition

Poly(ionic liquid)s (PILs) bearing high ionic densities are promising candidates for carbon dioxide (CO2) fixation. However, efficient and metal-free methods for boosting the catalytic efficiencies of PILs are still challenging. In this study, a novel family of poly(ionic liquid)-coated carbon nanotube nanoarchitectures (CNTs@PIL) were facilely prepared via a noncovalent and in-situ polymerization method. The effects of different carbon nanotubes (CNTs) and PILs on the structure, properties, and catalytic performance of the composite catalysts were systematically investigated. Characterizations and experimental results showed that hybridization of PIL with hydroxyl- or carboxyl-functionalized CNTs (CNT-OH, CNT-COOH) endows the composite catalyst with increased porosity, CO2 capture capacity, swelling ability and diffusion rate with respect to individual PIL, and allows the CNTs@PIL to provide H-bond donors for the synergistic activation of epoxides at the interfacial layer. Benefiting from these merits, the optimal composite catalyst (CNT-OH@PIL) delivered a super catalytic efficiency in the cycloaddition of CO2 to propylene oxide, which was over 4.5 times that of control PIL under metal- and co-catalyst free conditions. Additionally, CNT-OH@PIL showed high carbon dioxide/nitrogen (CO2/N2) adsorptive selectivity and could smoothly catalyze the cycloaddition reaction with a simulated flue gas (15% CO2 and 85% N2). Furthermore, the CNT-OH@PIL exhibited broad substrate tolerance and could be readily recycled and efficiently reused at least 12 times. Hybridization of PIL with functionalized CNTs provides a feasible approach for boosting the catalytic performance of PIL-based solid catalysts for CO2 fixation.

Diamide-linked imidazolyl Poly(dicationic ionic liquid)s for the conversion of CO2 to cyclic carbonates under ambient pressure

The ionic active centers and hydrogen-bond donors (HBDs) in heterogeneous catalytic materials are highly beneficial for enhancing the interaction between solid-liquid-gas three-phase interfaces and promoting effective fixation of carbon dioxide (CO2). Diamide-linked imidazolyl poly(dicationic ionic liquid)s catalysts PIMDILs (PMAIL-x and PBAIL-2) were synthesized through the copolymerization of diamide-linked imidazolyl dicationic ionic liquids (IMDILs) with divinylbenzene (DVB), which successfully enable the simultaneous construction of high-density and uniformly distributed ionic active centers (2.014-4.883 mmol g-1) and hydrogen-bond donors (HBDs). The as-synthesized PIMDILs present excellent catalytic activity in promoting the cycloaddition of CO2 with epoxides. PMAIL-2 could convert epichlorohydrin (ECH) with a quantitative conversion of 99.8 % (selectivity > 99 %) under ambient pressure. Furthermore, only a decrease in activity of 5 % was observed even after six cycles of recycling. The excellent conversions (>97.3 %) were achieved for various terminal substituted epoxides. The experimental and characterization results reveal that the high-density ionic active centers and amide HBDs can effectively activate the reaction substrates, their synergistic effect plays a crucial role at the catalyst interface. This work is expected to provide some useful insights for the rational construction of heterogeneous catalysts for CO2 conversion.

Poly(ionic liquid) nanovesicles via polymerization induced self-assembly and their stabilization of Cu nanoparticles for tailored CO2 electroreduction

Herein, we report a straightforward, scalable synthetic route towards poly(ionic liquid) (PIL) homopolymer nanovesicles (NVs) with a tunable particle size of 50 to 120 nm and a shell thickness of 15 to 60 nm via one-step free radical polymerization induced self-assembly. By increasing monomer concentration for polymerization, their nanoscopic morphology can evolve from hollow NVs to dense spheres, and finally to directional worms, in which a multilamellar packing of PIL chains occurred in all samples. The transformation mechanism of NVs' internal morphology is studied in detail by coarse-grained simulations, revealing a correlation between the PIL chain length and the shell thickness of NVs. To explore their potential applications, PIL NVs with varied shell thickness are in situ functionalized with ultra-small (1 ∼ 3 nm in size) copper nanoparticles (CuNPs) and employed as electrocatalysts for CO₂ electroreduction. The composite electrocatalysts exhibit a 2.5-fold enhancement in selectivity towards C₁ products (e.g., CH₄), compared to the pristine CuNPs. This enhancement is attributed to the strong electronic interactions between the CuNPs and the surface functionalities of PIL NVs. This study casts new aspects on using nanostructured PILs as new electrocatalyst supports in CO₂ conversion to C₁ products.