Harnessing the Hybridization of a Metal-Organic Framework and Superbase-Derived Ionic Liquid for High-Performance Direct Air Capture of CO2.

Direct air capture (DAC) of CO2 has emerged as the most promising "negative carbon emission" technologies. Despite being state-of-the-art, sorbents deploying alkali hydroxides/amine solutions or amine-modified materials still suffer from unsolved high energy consumption and stability issues. In this work, composite sorbents are crafted by hybridizing a robust metal-organic framework (Ni-MOF) with superbase-derived ionic liquid (SIL), possessing well maintained crystallinity and chemical structures. The low-pressure (0.4 mbar) volumetric CO2 capture assessment and a fixed-bed breakthrough examination with 400 ppm CO2 gas flow reveal high-performance DAC of CO2 (CO2 uptake capacity of up to 0.58 mmol g-1 at 298 K) and exceptional cycling stability. Operando spectroscopy analysis reveals the rapid (400 ppm) CO2 capture kinetics and energy-efficient/fast CO2 releasing behaviors. The theoretical calculation and small-angle X-ray scattering demonstrate that the confinement effect of the MOF cavity enhances the interaction strength of reactive sites in SIL with CO2 , indicating great efficacy of the hybridization. The achievements in this study showcase the exceptional capabilities of SIL-derived sorbents in carbon capture from ambient air in terms of rapid carbon capture kinetics, facile CO2 releasing, and good cycling performance.

High-Performance CO2 Capture from Air by Harnessing the Power of CaO- and Superbase-Ionic-Liquid-Engineered Sorbents.

Direct air capture (DAC) of CO2 by solid porous materials represents an attractive "negative emission" technology. However, state-of-the-art sorbents based on supported amines still suffer from unsolved high energy consumption and stability issues. Herein, taking clues from the CO2 interaction with superbase-derived ionic liquids (SILs), high-performance and tunable sorbents in DAC of CO2 was developed by harnessing the power of CaO- and SIL-engineered sorbents. Deploying mesoporous silica as the substrate, a thin CaO layer was first introduced to consume the surface-OH groups, and then active sites with different basicities (e. g., triazolate and imidazolate) were introduced as a uniformly distributed thin layer. The as-obtained sorbents displayed high CO2 uptake capacity via volumetric (at 0.4 mbar) and breakthrough test (400 ppm CO2 source), rapid interaction kinetics, facile CO2 releasing, and stable sorption/desorption cycles. Operando diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS) analysis under simulated air atmosphere and solid-state NMR under 13 CO2 atmosphere demonstrated the critical roles of the SIL species in low-concentration CO2 capture. The fundamental insights obtained in this work provide guidance on the development of high-performance sorbents in DAC of CO2 by leveraging the combined advantages of porous solid scaffolds and the unique features of CO2 -philic ionic liquids.

Construction of Boron- and Nitrogen-Enriched Nanoporous π-Conjugated Networks Towards Enhanced Hydrogen Activation.

Boron-enriched scaffolds have demonstrated unique features and promising performance in the field of catalysis towards the activation of small gas molecules. However, there is still a lack of facile approaches capable of achieving high B doping and abundant porous channels in the targeted catalysts. Herein, construction of boron- and nitrogen-enriched nanoporous π-conjugated networks (BN-NCNs) was achieved via a facile ionothermal polymerization procedure with hexaazatriphenylenehexacarbonitrile [HAT(CN)6 ] sodium borohydride as the starting materials. The as-produced BN-NCN scaffolds were featured by high heteroatoms doping (B up to 23 wt. % and N: up to 17 wt. %) and permanent porosity (surface area up to 759 m2 g-1 mainly contributed by micropores). With the unsaturated bonded B species acting as the active Lewis acid sites and defected N species acting as the active Lewis base sites, those BN-NCNs delivered attractive catalytic performance towards H2 activation/dissociation in both gaseous and liquid phase, acting as efficient metal-free heterogeneous frustrated Lewis pairs (FLPs) catalysts in hydrogenation procedures.

Construction of Fluorine- and Piperazine-Engineered Covalent Triazine Frameworks Towards Enhanced Dual-Ion Positive Electrode Performance.

Organic positive electrodes featuring lightweight and tunable energy storage modes by molecular structure engineering have promising application prospects in dual-ion batteries. Herein, a series of highly porous covalent triazine frameworks (CTFs) were synthesized under ionothermal conditions using fluorinated aromatic nitrile monomers containing a piperazine ring. Fluorinated monomers can result in more defects in CTFs, leading to a higher surface area up to 2515 m2 g-1 and a higher N content of 11.34 wt % compared to the products from the non-fluorinated monomer. The high surface area and abundant redox sites of these CTFs afforded high specific capacities (up to 279 mAh g-1 at 0.1 A g-1 ), excellent rate performance (89 mAh g-1 at 5 A g-1 ), and durable cycling performance (92.3 % retention rate after 500 cycles at 2.0 A g-1 ) as dual-ion positive electrodes.

Barium Hexaferrite (BaFe12O19) Nanoparticles as Highly Active and Magnetically Recoverable Catalyst for Selective Epoxidation of Styrene to Styrene Oxide.

Herein, we are reporting the use of pure single phase barium hexaferrite (BaFe12O19) nanoparticles as an efficient catalyst for epoxidation of styrene. BaFe12O19 nanocatalysts exhibit high conversion of styrene with excellent selectivity of styrene oxide formation. Easy method of preparation, capability of catalyzing the epoxide reaction of styrene to styrene oxide with excellent styrene conversion (~91%) and high styrene oxide selectivity (~86.5%), easy magnetic separation and very good reusability make the synthesized BaFe12O19 nanocatalyst an excellent catalyst for this reaction. To the best of our knowledge, this is the first time the use of BaFe12O19 as catalyst for this reaction has been reported.

Synthesis of Various Ferrite (MFe2O4) Nanoparticles and Their Application as Efficient and Magnetically Separable Catalyst for Biginelli Reaction.

Herein, we reports the application of various spinel ferrite nanoparticles, MFe2O4 (M = Co, Ni, Cu, Zn), as efficient catalyst for Biginelli reaction. All ferrite nanoparticles were synthesized using a novel aqueous solution based method. It was observed that, the catalytic activity of the ferrite nanoparticles followed the decreasing order of CoFe2O4 > CuFe2O4 > NiFe2O4 > ZnFe2O4. The most important feature of these ferrite nanocatalysts is that, these nanoparticles can directly be used as catalyst and no surface modification or functionalization is required. These ferrite nanoparticles are easily separable from reaction mixture after reaction by using a magnet externally. Easy synthesis methodology, high catalytic activity, easy magnetic separation and good reusability make these ferrite nanoparticles attractive catalysts for Biginelli reaction.

Synthesis of multifunctional CuFe2O4-reduced graphene oxide nanocomposite: an efficient magnetically separable catalyst as well as high performance supercapacitor and first-principles calculations of its electronic structures.

Here, we report an 'in situ' co-precipitation reduction based synthetic methodology to prepare CuFe2O4 nanoparticle-reduced graphene oxide (CuFe2O4-RGO) nanocomposites. First principles calculations based on Density Functional Theory (DFT) were performed to obtain the electronic structures and properties of CuFe2O4, graphene and CuFe2O4-graphene composites, and to understand the interfacial interaction between CuFe2O4 and graphene in the composite. The synergistic effect, which resulted from the combination of the unique properties of RGO and CuFe2O4 nanoparticles, was exploited to design a magnetically separable catalyst and high performance supercapacitor. It has been demonstrated that the incorporation of RGO in the composite enhanced its catalytic properties as well as supercapacitance performance compared with pure CuFe2O4. The nanocomposite with 96 wt% CuFe2O4 and 4 wt% RGO (96CuFe2O4-4RGO) exhibited high catalytic efficiency towards (i) reduction of 4-nitrophenol to 4-aminophenol, and (ii) epoxidation of styrene to styrene oxide. For both of these reactions, the catalytic efficiency of 96CuFe2O4-4RGO was significantly higher than that of pure CuFe2O4. The easy magnetic separation of 96CuFe2O4-4RGO from the reaction mixture and good reusability of the recovered catalyst also showed here. 96CuFe2O4-4RGO also demonstrated better supercapacitance performance than pure CuFe2O4. 96CuFe2O4-4RGO showed specific capacitance of 797 F g-1 at a current density of 2 A g-1, along with ∼92% retention for up to 2000 cycles. To the best of our knowledge, this is the first investigation on the catalytic properties of CuFe2O4-RGO towards the reduction of 4-nitrophenol and the epoxidation reaction, and DFT calculations on the CuFe2O4-graphene composite have been reported.

A facile synthesis methodology for preparation of Ag-Ni-reduced graphene oxide: a magnetically separable versatile nanocatalyst for multiple organic reactions and density functional study of its electronic structures.

Here, we report a simple 'in situ' co-precipitation reduction synthesis method for the preparation of nanocatalysts composed of Ag, Ni nanoparticles, and reduced graphene oxide (RGO). First-principles calculations based on Density Functional Theory (DFT) were performed to obtain the electronic structures and properties of Ag-Ni-graphene superlattice and to understand the interfacial interactions which exist at the interface between Ag, Ni, and graphene. The catalytic performance of the synthesized catalysts (Ag x Ni(1-x)) y RGO(100-y) were evaluated for four reactions (i) reduction of 4-nitrophenol (4-NP) in the presence of excess NaBH4 in aqueous medium, (ii) A3 coupling reaction for the synthesis of propargylamines, (iii) epoxidation of styrene, and (iv) 'Click reaction' for the synthesis of 1,2,3-triazole derivatives. For all of these reactions the catalyst composed of Ag, Ni, and RGO, exhibited significantly higher catalytic activity than that of pure Ag, Ni, and RGO. Moreover, an easy magnetic recovery of this catalyst from the reaction mixture after completion of the catalytic reactions and the good reusability of the recovered catalyst is also reported here. To the best of our knowledge, this is the first time the demonstration of the versatile catalytic activity of (Ag x Ni(1-x)) y RGO(100-y) towards multiple reactions, and the DFT study of its electronic structure have been reported.