Enzyme catalysis, as a green, efficient process, displays exceptional functionality, adaptivity and sustainability. Multi-enzyme catalysis, which can accomplish the tandem synthesis of valuable materials/chemicals from renewable feedstocks, establishes a bridge between single-enzyme catalysis and whole-cell catalysis. Multi-enzyme catalysis occupies a unique and indispensable position in the realm of biological reactions for energy and environmental applications. Two complementary strategies, i.e., compartmentalization and substrate channeling, have been evolved by living organisms for implementing the complex in vivo multi-enzyme reactions (MERs), which have been applied to construct multi-enzyme catalytic systems (MECSs) with superior catalytic activity and stabilities in practical biocatalysis. This tutorial review aims to present the recent advances and future prospects in this burgeoning research area, stressing the features and applications of the two strategies for constructing MECSs and implementing in vitro MERs. The concluding remarks are presented with a perspective on the construction of MECSs through rational combination of compartmentalization and substrate channeling.

Graphitic carbon nitride (g-C 3 N 4 ) is an emergent metal-free photocatalyst because of its band position, natural abundance, and facile preparation. Synergetic intensification of charge generation and charge transfer of g-C 3 N 4 to increase solar-to-chemical efficiency remains a hot yet challenging issue. Herein, a nanoshell with two moieties of α-Fe 2 O 3 and carbon (C) is in situ formed on the surface of a g-C 3 N 4 core through calcination of Fe 3+ /polyphenol-coated melamine, thus acquiring g-C 3 N 4 @α-Fe 2 O 3 /C core@shell photocatalysts. The α-Fe 2 O 3 moiety acts as an additional photosensitizer, offering more photogenerated electrons, whereas the C moiety bridges a "highway" to facilitate the electron transfer either from α-Fe 2 O 3 moiety to g-C 3 N 4 or from g-C 3 N 4 to C moiety. By tuning the proportion of these two moieties in the nanoshell, a photocurrent density of 3.26 times higher than pristine g-C 3 N 4 is obtained. When utilized for photocatalytic regeneration of reduced nicotinamide adenine dinucleotide (NADH, a dominant cofactor in biohydrogenation reaction), g-C 3 N 4 @α-Fe 2 O 3 /C exhibits an equilibrium NADH yield of 76.3% with an initial reaction rate (r) of 7.7 mmol h −1 g −1 , among the highest r for photocatalytic NADH regeneration ever reported. Manipulating the coupling between charge generation and charge transfer may offer a facile, generic strategy to improve the catalytic efficiency of a broad range of photocatalysts other than g-C 3 N 4 .

Artificial photosynthesis holds promise in producing solar fuels and chemicals. Although encouraging achievements have been made in the development of catalysts for reaction/ process modules in artificial photosynthesis, constructing a highly compatible complex reaction system remains a distant prospect. Herein, an artificial thylakoid is proposed and constructed by decorating the inner wall of protamine−titania (PTi) microcapsules with cadmium sulfide quantum dots (CdS QDs) for the photobiocoupled reduction of carbon dioxide (CO 2 ) via a single enzyme (formate dehydrogenase) and multiple enzymes (formate/formaldehyde/alcohol dehydrogenases). The size-selective capsule wall compartmentalizes photocatalytic oxidation and biocatalytic reduction, creating well-directed reaction sequences and protecting enzymes from deactivation. The favorable electronic coupling and band structure between CdS and PTi separate holes and electrons to afford an NADH regeneration rate of 4226 ± 121 μmol g −1 h −1 and optimized yield of 93.03 ± 3.84%. The photobiocoupled system achieves formate and methanol outputs of 1500 and 99 μM h −1 with a single enzyme and multiple enzymes, respectively. Our study may exploit a method for the construction of complex artificial catalytic systems with multiple reactions.

Solar energy conversion by photocatalysis holds promise in energy supply, but its efficiency is hindered by the mismatch in charge generation, transfer, and utilization. In natural photosynthesis, photosystem I (PSI) exhibits an intrinsic quantum efficiency of nearly 100% in solar energy conversion. The elaborate synergy of electron transfer and electron utilization guarantees the conversion of unstable excited electrons to stable electrons in reduced nicotinamide adenine dinucleotide phosphate (NADPH). To demonstrate this in vitro, we report a design of core−shell metal−organic frameworks (MOFs) as an "electron buffer tank" to coordinate electron transfer and electron utilization in photocatalysis. The electrons are generated via the irradiation on photosensitizers (2-aminoterephthalic acid, NH 2 -BDC) in the core and then transferred to Zr 6 O 8 clusters on the shell through the light-induced ligand-to-metal charge transfer mechanism. Neighboring reaction centers, [Cp*Rh(bpydc)H 2 O] 2+ , on the MOFs behave as the electron buffer tank and store these electrons in the form of hydrides for subsequent regeneration of reduced nicotinamide adenine dinucleotide (NADH). The electron lifetime is prolonged from nanoseconds to seconds, leading to 2.27-fold enhancement of electron availability and 2.08-fold enhancement of activity compared to the homogeneous reaction counterpart. The coupling of NADH regeneration and enzyme catalysis further enables the asymmetric reduction of carbonyl to chiral amine. The electron buffer tank concept may offer a generic strategy to coordinate mass transfer and chemical reaction in a broad range of catalytic processes.

In-depth understanding and rational manipulation of the electron transfer process and molecule diffusion process are critical to promote the overall photocatalytic efficiency. In our study, core@shell photocatalysts that embody graphitic carbon nitride (GCN) core and amorphous titania (a-TiO2) nanoshell are prepared to elucidate and coordinate the electron transfer and molecule diffusion for the regeneration of nicotinamide adenine dinucleotide (NADH) with [Cp*Rh­(bpy)­H2O]2+ as the redox mediator. The GCN core absorbs visible light to generate electron–hole pairs, whereas the a-TiO2 nanoshell facilitates the transfer of photogenerated electrons from GCN to the a-TiO2 surface for NADH regeneration, which also enables the diffusion of electron donor molecules (triethanolamine, TEOA) from the a-TiO2 surface to GCN for consuming the holes left on GCN. The transfer of photogenerated electrons and the diffusion of electron donor molecules are coordinated by finely tuning the thickness of the a-TiO2 nanoshell. Under the optimized nanoshell thickness of ∼2.1 nm, the GCN@a-TiO2 photocatalyst exhibits the highest NADH regeneration yield of 82.1% after a 10 min reaction under LED light (405 nm), over 200% higher than that of the GCN photocatalyst. Combined with the highly controllable and mild features of the bioinspired mineralization method, our study may offer a facile and generic strategy to design high performance photocatalysts through rational coordination of different substances/species transport processes.

Testing the distance-sum-rule in strong lensing systems provides an interesting method to determine the curvature parameter Ω k using more local objects. In this paper, we apply this method to a quite recent data set of strong lensing systems in combination with intermediate-luminosity quasars calibrated as standard rulers. In the framework of three types of lens models extensively used in strong lensing studies (SIS model, power-law spherical model, and extended power-law lens model), we show that the assumed lens model has a considerable impact on the cosmic curvature constraint, which is found to be compatible or marginally compatible with the flat case (depending on the lens model adopted). Analysis of low, intermediate and high-mass sub-samples defined according to the lens velocity dispersion demonstrates that, although it is not reasonable to characterize all lenses with a uniform model, such division has little impact on cosmic curvature inferred. Finally, thinking about future when massive surveys will provide their yields, we simulated a mock catalog of strong lensing systems expected to be seen by the LSST, together with a realistic catalog of quasars. We found that with about 16000 such systems, combined with the distance information provided by 500 compact milliarcsecond radio sources seen in future radio astronomical surveys, one would be able to constrain the cosmic curvature with an accuracy of ∆Ω k ≃ 10 −3 , which is comparable to the precision of Planck 2015 results.

This investigation considers branched alkyl alcohol propoxylated sulfate surfactants as candidates for chemcial enhanced oil recovery (EOR) applications. Results show that these anionic surfactants may be preferred candidates for EOR as they can be effective at creating low interfacial tension (IFT) at dilute concentrations, without requiring an alkaline agent or cosurfactant. In addition, some of the formulations exhibit a low IFT at high salinity, and hence may be suitable for use in more saline reservoirs. Adsorption tests onto kaolinite clay indicate that the loss of these surfactants can be comparable to or greater than other types of anionic surfactants. Surfactant performance was evaluated in oil recovery core flood tests. Selected formulations recovered 35-50 % waterflood residual oil even with dilute 0.2 wt% surfactant concentrations from Berea sandstone cores.

Photoenzymatic coupled catalysis, integrating semiconductor photocatalysis and enzymatic catalysis, exhibits great potential for light-driven synthesis. To make photocatalyst and enzyme at play concertedly, nicotinamide-based cofactors have been widely used as electron carrier. However, these cofactors are easily oxidized into enzymatically inactive form by photo-generated holes. Herein, oxidation mechanism of NADH, one typical nicotinamide-based cofactor, by photo-generated holes was reported. With CdS, g-C3N4 and BiVO4 as hole generators, NADH is oxidized into NAD + or fragmented into ADP-ribose derivatives through multi-step electron transfer. Importantly, fragmentation reaction is inhibited with dopamine and neutral red to coordinate electron transfer between NADH and photo-generated holes.