Fischer–Tropsch synthesis (FTS) is an important catalytic process for liquid fuel generation, which converts coal/shale gas/biomass-derived syngas (a mixture of CO and H2) to oil. While FTS is thermodynamically favored at low temperature, it is desirable to develop a new catalytic system that could allow working at a relatively low reaction temperature. In this article, we present a one-step hydrogenation–reduction route for the synthesis of Pt–Co nanoparticles (NPs) which were found to be excellent catalysts for aqueous-phase FTS at 433 K. Coupling with atomic-resolution scanning transmission electron microscopy (STEM) and theoretical calculations, the outstanding activity is rationalized by the formation of Co overlayer structures on Pt NPs or Pt–Co alloy NPs. The improved energetics and kinetics from the change of the transition states imposed by the lattice mismatch between the two metals are concluded to be the key factors responsible for the dramatically improved FTS performance.

Pd nanoparticles (NPs) with a small size and narrow size distribution were prepared from the decomposition of Pd(OAc)2 in a series of hydroxyl-functionalized ionic liquids (ILs) comprising the 1-(2′-hydroxylethyl)-3-methylimidazolium cation and various anions, viz. [C2OHmim][OTf] (2.4 ± 0.5 nm), [C2OHmim][TFA] (2.3 ± 0.4 nm), [C2OHmim][BF4] (3.3 ± 0.6 nm), [C2OHmim][PF6] (3.1 ± 0.7 nm) and [C2OHmim][Tf2N] (4.0 ± 0.6 nm). Compared with Pd NPs isolated from the non-functionalized IL, [C4mim][Tf2N] (6.2 ± 1.1 nm), it would appear that the hydroxyl group accelerates the formation of the NPs, and also helps to protect the NPs from oxidation once formed. Based on the amount of Pd(OAc)2 that remains after NP synthesis (under the given conditions) the ease of formation of the Pd NPs in the [C2OHmim]+-based ILs follows the trend [Tf2N]−, [PF6]− > [BF4]− > [OTf]− > [TFA]−. Also, the ability of the [C2OHmim]+-based ILs to prevent the Pd NPs from undergoing oxidation follows the trend [Tf2N]− > [PF6]− > [TFA]− > [OTf]− > [BF4]−. DFT calculations were employed to rationalize the interactions between Pd NPs and the [C2OHmim]+ cation and the various anions.

A combination of in situ time-resolved DXAFS and ICP-MS techniques reveals that the formation process of Rh nanoparticles (NPs) from rhodium trichloride trihydrate (RhCl3·3H2O) in ethylene glycol with polyvinylpyrrolidone (PVP) at elevated temperature is a first-order reaction, which indicates that uniform size Rh NPs appear consecutively and these Rh NPs do not aggregate with each other.

Nanoparticle (NP) catalysis in liquid phase, which is usually called “soluble” NP catalysis, is an old topic but is now well advanced due to the great progress in nano-chemistry and nano-technology in green chemistry. After a short introduction of the history, this review describes the current status of NP catalysis in solvents and then discusses the main drawbacks hindering the particles from industrial practice. Efficiency, stability, sustainability, and recyclability (ESSR) criteria were suggested to evaluate NP catalytic systems. A state-of-the-art approach to satisfy ideal ESSR criteria is to produce cohesion over the individual contributions of metal center, stabilizer and solvent (MSS), i.e., a cohesive MSS approach. Based on reported examples, the roles that the metal core, the stabilizer and the solvent play in NP catalysis are discussed in detail. For clarity, a fairly complete list of NP catalytic systems in various green solvents reported in recent decade is provided.

The Fe nanoparticles dispersed in polyethylene glycol (PEG) can catalyze Fischer–Tropsch (F-T) synthesis at mild conditions (150 °C, 2.0 MPa H2, 1.0 MPa CO) with an activity as high as 1.5 molCO molFe−1 h−1. The F-T products, hydrocarbons, are insoluble in the green solvent PEG, and could be easily separated from the reaction mixture.

Two thermoresponsive polymers based on alkyl modified poly-vinylpyrrolidone (PVP) that exhibit very sensitive and reversible temperature-dependant water solubility are described. The application of these polymers as Au nanocatalyst stabilizers leads to a “smart” thermoresponsive Au nanoparticlecatalyst.

A series of new monomers with different substituents at the 3-position of N-vinyl-2-pyrrolidone (NVP) were synthesized. The substituents include simple alkyl (methyl, ethyl, propyl, and isopropyl), ether (methoxy ethyl and ethoxy ethyl), and functional groups (e.g., aldehyde, epoxy, and acetylene). These monomers were (co)polymerized radically to produce a family of (co)polymers based on poly(N-vinyl-2-pyrrolidone) (PVP), and the copolymer compositions could be controlled through varying comonomer feed ratio. When the monomers are substituted with ethyl-, methyl-, or ether-containing alkyl chains, their homopolymers are soluble in cold water but display sensitive and reversible phase transition upon heating to a cloud point temperature (CP). Control over CP of homopolymers was achieved by changing the hydrophilicity of the substituents. CP could also be tuned by copolymerization of different monomers or adding NaCl to the polymer aqueous solution. The mechanism of the thermoresponsive properties was studied by temperature-dependent 1H NMR and microcalorimetry. The results confirmed that the phase transitions of (co)polymers bearing ether substituents were less cooperative with lower phase transition enthalpy and less dehydration even at temperatures well above the CP, and the transition is predominately liquid to liquid. In addition, aldehyde, epoxy, and acetylene groups were introduced to the (co)polymer chains as reactive groups; model reactions of these groups with other molecules were very efficient and simple. Thus, these polymers can subsequently be modified to impart additional functionality to be used as thermoresponsive polymers for bioconjugation. Finally, these polymers are demonstrated to be at least as biocompatible as PVP.

Seven soluble metal nanoparticle catalysts including Pt, Ru, Rh, Pd, Ir, Ag and Au were synthesized and studied for the aqueous-phase selective oxidation of non-activated alcohols under atmospheric pressure of O2. The effects of particle size were examined on the Pt catalysts with mean diameters of 1.5–4.9 nm. Pt nanoparticles efficiently catalyze the aerobic oxidation of alicyclic and aliphatic alcohols, in particular, primary aliphatic alcohols in the absence of any base. The particle sizes of the Pt catalysts strongly influence their activities, and the one of 1.5 nm exhibits much higher turnover frequencies. In comparison with the other metals examined in this work, it is concluded that Pt is the best metal of choice for the aerobic alcohol oxidation. Aliphatic primary alcohols reacts on the Pt catalysts more preferentially over their isomeric secondary alcohols with increasing their chain length or as they coexist. These steric effects, and the observed kinetic isotope effects with 1-C4H9OD and 1-C4D9OD are consistent with the general alcohol oxidation mechanism, which includes a sequence of elementary steps involving the formation of the alcoholate intermediates in quasi-equilibrated 1-C4H9OH dissociation on the Pt surfaces and the rate-determining hydrogen abstraction from the alcoholates. The inhibiting effects of hydroquinone, a typical radical scavenger, are indicative of the formation of radical intermediates in the H-abstraction step.

Systematic fabrication of nanoparticle stabilizers can substantially modify the properties of prepared nanoparticles; here the synthesis of solubility adjustable nanoparticles is achieved by employing a family of polarity modulated stabilizers.

Liquid-phase synthesis of methyl formate (MF) was achieved by green carbonylation of methanol with CO on a soluble copper nanocluster catalyst with high activities (e.g. 2.7–6.1 molMF molCu−1 h−1) and 100% MF selectivities under mild reaction conditions (353–443 K, 0.3–3.0 MPa CO), showing that the Cu nanoclusters can potentially replace the caustic catalysts of alkaline metal alkoxides (e.g. CH3ONa), required for the current carbonylation process in industry.

A soluble Pt nanocluster catalyst (Pt-GLY) is efficient in the absence of base for aqueous-phase aerobic oxidation of, in particular, non-activated alcohols with high recyclability.

A family of novel ionic liquids with amino acids and their derivatives as cations and environmentally benign materials as anions have been synthesized using easy preparation techniques. The ionic liquids obtained have the same characteristics as conventional imidazolium ionic liquids and the same chiralities as natural amino acids. Thermal stabilities, phase behaviour, viscosities and miscibilities of the representative family members have been investigated, generally showing no difference from conventional ionic liquids. These amino acid ionic liquids may be used as catalysts and “fully green” solvents in the cycloaddition of cyclopentadiene to methyl acrylate, which is a typical Diels–Alder reaction. This approach to treating amino acids and their derivatives can serve as an alternative to traditional ionic liquids having synthetic chemical components.

Two families of a new generation of ionic liquids, in which the chiral cations are directly derived from naturally occurring α-amino acids and α-amino acid ester salts, have been obtained via very simple preparations.

Pyridine and ethanenitrile can be used as molecular probes to measure the Lewis acidities of ionic liquids by monitoring the shift of IR absorption bands near 1450 cm−1 for pyridine and in the range 2250–2340 cm−1 for ethanenitrile.

Rhodium nanoparticles stabilized by the ionic-liquid-like copolymer poly[(N-vinyl-2-pyrrolidone)-co-(1-vinyl-3-butylimidazolium chloride)] were used to catalyze the hydrogenation of benzene and other arenes in ILs. The nanoparticle catalysts can endure forcing conditions (75 °C, 40 bar H2), resulting in high reaction rates and high conversions compared with other nanoparticles that operate in ILs. The hydrogenation of benzene attained record total turnovers of 20,000, and the products were easily separated without being contaminated by the catalysts. Other substrates, including alkyl-substituted arenes, phenol, 4-n-propylphenol, 4-methoxylphenol, and phenyl-methanol, were studied and in most cases were found to afford partially hydrogenated products in addition to cyclohexanes. In-depth investigations on reaction optimization, including characterization of copolymers, transmission electron microscopy, and an infrared spectroscopic study of nanocatalysts, were also undertaken.

An ionic-liquid-like copolymer was used to stabilize the platinum nanoclusters in ionic liquids. Catalytic performance was tested by the selective hydrogenation of o-chloronitrobenzene. Platinum catalysts Pt-I (5.1 nm) and Pt-II (1.7 nm) both exhibited excellent activity and selectivity for the reaction and were recycled with the activity and selectivity preserved. An unprecedented total turnover number (>25,900) was obtained on the Pt-II catalyst. Infrared spectroscopy, transmission electron microscopy, X-ray diffraction characterizations, and density functional theory calculations were used to study the catalysts.

A biphasic approach to the dehydroaromatization of bioderived limonene into water-insoluble p-cymene using soluble Pd nanoparticle catalysts in an aqueous phase (⩾150 °C, 2 bar H2) was successfully achieved with a conversion of 93% and a selectivity of 82%. The Pd nanoparticles, operating under forcing conditions (180 °C, 2 bar H2), can be recycled at least four times without noticeable degradation. The effects of temperature, pressure, reaction time, pH, catalyst concentration, metal type, the type and amount of polymer stabilizer, and the preparation method were systematically investigated to optimize the process and provide insight into the mechanisms involved.

A biphasic approach to the dehydroaromatization of bioderived limonene into water-insoluble p-cymene using soluble Pd nanoparticle catalysts in an aqueous phase (⩾150 °C, 2 bar H2) was successfully achieved with a conversion of 93% and a selectivity of 82%. The Pd nanoparticles, operating under forcing conditions (180 °C, 2 bar H2), can be recycled at least four times without noticeable degradation. The effects of temperature, pressure, reaction time, pH, catalyst concentration, metal type, the type and amount of polymer stabilizer, and the preparation method were systematically investigated to optimize the process and provide insight into the mechanisms involved.

Pd nanoparticles (NPs) with a small size and narrow size distribution were prepared from the decomposition of Pd(OAc)2 in a series of hydroxyl-functionalized ionic liquids (ILs) comprising the 1-(2′-hydroxylethyl)-3-methylimidazolium cation and various anions, viz. [C2OHmim][OTf] (2.4 ± 0.5 nm), [C2OHmim][TFA] (2.3 ± 0.4 nm), [C2OHmim][BF4] (3.3 ± 0.6 nm), [C2OHmim][PF6] (3.1 ± 0.7 nm) and [C2OHmim][Tf2N] (4.0 ± 0.6 nm). Compared with Pd NPs isolated from the non-functionalized IL, [C4mim][Tf2N] (6.2 ± 1.1 nm), it would appear that the hydroxyl group accelerates the formation of the NPs, and also helps to protect the NPs from oxidation once formed. Based on the amount of Pd(OAc)2 that remains after NP synthesis (under the given conditions) the ease of formation of the Pd NPs in the [C2OHmim]+-based ILs follows the trend [Tf2N]−, [PF6]− > [BF4]− > [OTf]− > [TFA]−. Also, the ability of the [C2OHmim]+-based ILs to prevent the Pd NPs from undergoing oxidation follows the trend [Tf2N]− > [PF6]− > [TFA]− > [OTf]− > [BF4]−. DFT calculations were employed to rationalize the interactions between Pd NPs and the [C2OHmim]+ cation and the various anions.

Two thermoresponsive polymers based on alkyl modified poly-vinylpyrrolidone (PVP) that exhibit very sensitive and reversible temperature-dependant water solubility are described. The application of these polymers as Au nanocatalyst stabilizers leads to a “smart” thermoresponsive Au nanoparticlecatalyst.

Systematic fabrication of nanoparticle stabilizers can substantially modify the properties of prepared nanoparticles; here the synthesis of solubility adjustable nanoparticles is achieved by employing a family of polarity modulated stabilizers.

A combination of in situ time-resolved DXAFS and ICP-MS techniques reveals that the formation process of Rh nanoparticles (NPs) from rhodium trichloride trihydrate (RhCl3·3H2O) in ethylene glycol with polyvinylpyrrolidone (PVP) at elevated temperature is a first-order reaction, which indicates that uniform size Rh NPs appear consecutively and these Rh NPs do not aggregate with each other.

A soluble Pt nanocluster catalyst (Pt-GLY) is efficient in the absence of base for aqueous-phase aerobic oxidation of, in particular, non-activated alcohols with high recyclability.