Gas-solid Reaction Research Articles

Conceptual and Practical Aspects of Metal-Organic Frameworks for Solid-Gas Reactions.

The presence of site-isolated and well-defined metal sites has enabled the use of metal-organic frameworks (MOFs) as catalysts that can be rationally modulated. Because MOFs can be addressed and manipulated through molecular synthetic pathways, they are chemically similar to molecular catalysts. They are, nevertheless, solid-state materials and therefore can be thought of as privileged solid molecular catalysts that excel in applications involving gas-phase reactions. This contrasts with homogeneous catalysts, which are overwhelmingly used in the solution phase. Herein, we review theories dictating gas phase reactivity within porous solids and discuss key catalytic gas-solid reactions. We further treat theoretical aspects of diffusion within confined pores, the enrichment of adsorbates, the types of solvation spheres that a MOF might impart on adsorbates, definitions of acidity/basicity in the absence of solvent, the stabilization of reactive intermediates, and the generation and characterization of defect sites. The key catalytic reactions we discuss broadly include reductive reactions (olefin hydrogenation, semihydrogenation, and selective catalytic reduction), oxidative reactions (oxygenation of hydrocarbons, oxidative dehydrogenation, and carbon monoxide oxidation), and C-C bond forming reactions (olefin dimerization/polymerization, isomerization, and carbonylation reactions).

Modulating Dominant Facets of Pt through Multistep Selective Anchored on WC for Enhanced Hydrogen Evolution Catalysis.

Facilitating the exposure of the active crystal facets on the surfaces of composite catalysts is a representative route to promote catalytic activity. Based on a tailored galvanic replacement reaction, herein, a self-assembly route is reported to prepare Pt-WC/CNT with Pt (200) preferential orientation and well-dispersed structure, which are capable of substantially boosting electrocatalysis in hydrogen evolution reaction (HER). Formation mechanism reveals that the (200)-dominated Pt-based catalysts form in galvanic replacement reaction through selective anchored on WC, and the multistep galvanic replacement process plays a critical role to realize the Pt (200)-dominated growth in higher Pt loading catalyst. These unique structural features endow the Pt-WC/CNT with a high turnover frequency of 94.18 H2·s-1 at 100 mV overpotential, 7-fold higher than that of commercial Pt/C (13.55 H2·s-1), ranking it among the most active catalysts. In addition, this method, which combines with gas-solid reaction and galvanic replacement reaction, paves the way to scalable synthesis as Pt facets-controllable composite catalysts to challenge commercial Pt/C.

Experimental and numerical investigation of flame stabilization and pollutant formation in matrix stabilized ammonia-hydrogen combustion

Ammonia (NH3) is a carbon-free fuel that offers an attractive alternative for reducing greenhouse gas emissions. However, the slow flame speed, low heating value, and emissions of nitrogen-containing pollutants present significant issues for practical combustion applications. To address these issues, we investigate the use of matrix stabilized combustion. In this type of burner, combustion is performed within an inert porous ceramic foam, heat is recirculated by solid conduction and radiation, which enhances flame speed and combustion stabilization, thereby permitting combustion over a wide range of equivalence ratio conditions. We present a new porous media burner (PMB) capable of stabilizing NH3/air flames at ambient conditions. An extensive experimental characterization of the stability of this burner is conducted with up to 30% by volume of hydrogen (H2) in the fuel stream. A 15:1 turndown ratio is demonstrated, with a high thermal power density of 62MWm−3. Concentrations of NO, unburnt NH3, and H2 in the exhaust stream are measured. Two regimes are identified for low NO operation: rich and very lean. For rich conditions, NO emissions decrease with increasing equivalence ratio and decreasing H2 blending. Unburnt NH3 emissions follow opposite trends. These measurements are complemented by simulations in which the burner is represented by a coupled solid-gas reactor network. This model captures the burner’s pollutant emissions to good accuracy and is used to analyze the mechanisms of pollutant formation.

Atomistic Origins of Reversible Noncatalytic Gas-Solid Interfacial Reactions.

Noncatalytic gas-solid reactions are a large group of heterogeneous reactions that are usually assumed to occur irreversibly because of the strong driving force to favor the forward direction toward the product formation. Using the example of Ni oxidation into NiO with CO2, herein, we demonstrate the existence of the reverse element that results in the NiO reduction from the countering effect of the gaseous product of CO. Using in situ electron microscopy observations and atomistic modeling, we show that the oxidation process occurs via preferential CO2 adsorption along step edges that results in step-flow growth of NiO layers, and the presence of Ni atoms on the flat NiO surface promotes the nucleation of NiO layers. Simultaneously, the NiO reduction happens via preferential step-edge adsorption of CO that leads to the receding motion of atomic steps, and the presence of Ni vacancies in the NiO surface facilitates the CO-adsorption-induced surface pitting. Temperature and CO2 pressure effect maps are constructed to illustrate the spatiotemporal dynamics of the competing NiO redox reactions. These results demonstrate the rich gas-solid surface reaction dynamics induced by the coexisting forward and reverse reaction elements and have practical applicability in manipulating gas-solid reactions via controlling the gas environment or atomic structure of the solid surface to steer the reaction toward the desired direction.

Bimetal MOF-derived NiFe-P nanocomposites coupled with Cu3P nanoparticles to construct tandem electron transfer channels for photocatalytic hydrogen evolution

Finely modulated light-induced charge separation and transfer is a central challenge to achieve efficient photocatalysis. Although progress has been made in this field, most of the previous research works focused on the separation or migration of photogenerated carriers but did not build a bridge between the two. How to realize the strong driving and precise migration of carriers has become the focus of our work. We report an ingeniously designed ternary heterojunction. Taking NiFe-MOF as the “parent material”, the FeP4/NixPy heterojunction is derived in situ while maintaining the frame structure through gas-solid reaction, and finally the Z-type electron transfer is realized. With Cu3P anchoring spindle matrix, an electron transport tunnel is opened up in Cu3P/FeP4/NixPy ternary heterojunction under the action of p-n heterojunction built-in electric field driving and accurate energy band matching. The strong driving force of the built-in electric field provides an inexhaustible power for the transmission of electrons, and the fine series of electron transmission channels realizes the precise transmission of electrons. The above fine design makes the perfect fit between the built-in electric field and the electron transfer channel, which not only effectively improves the embarrassing situation of insufficient electron driving force of hydrogen evolution reaction in the previous research, but also makes up for the weakening of semiconductor reduction ability caused by the construction of traditional p-n heterostructures. This research work provides a new idea for the construction of multiple heterostructures and the design of fine interface engineering in the future.

Study of the anisotropic Sm2Fe17N3 powders with high performance

The strip casting technique was first used in this work to prepare the Sm2Fe17 parent alloys. Next, the Sm2Fe17N3 powders were synthesized using a gas–solid reaction of Sm2Fe17 powders with N2. Then, the anisotropic Sm2Fe17N3 powders with high performance were prepared by a surfactant-assisted grinding method in gasoline solvent. It was found that the coercivity (iHc) of ground powders increases with decreasing the average particle size (Dm), while the saturation magnetization (Ms) decreases. The maximum value of iHc of 17.5 kOe was obtained at the Dm = 1.3 µm. The ground powders with Dm of 3.1 µm show a remanence ratio (Mr/Ms) over 95% and a maximum energy product [(BH)max] of 35 MGOe. The Sm2Fe17N3 powder exhibited a very high iHc of 36.1 kOe at 10 K. Above 300 K, Sm2Fe17N3 powders mixed with epoxy resin showed a low remanence temperature coefficient of α(RT-100°C) = −0.077% °C−1.

Highly dispersed g-C3N4 on well-designed three-dimensional porous nanostructured ZrO2 for high-performance photocatalytic degradation and H2 production

A novel polymer-assisted freeze-drying method was adopted for preparing three-dimensional porous nanostructured ZrO2 (3DPZ) with macro self-supporting properties. Then, g-C3N4 was in-situ grown uniformly on the 3DPZ through a gas-solid reaction, forming 3D nanoporous ZrO2/g-C3N4 heterojunctions (3DP/ZC) with different g-C3N4 loadings that retained self-supporting characteristics. The kapp value of Rhodamine B (RhB) degradation and H2 evolution rate of the 3DP/ZC-2 under visible light reached 0.035 min−1 and 1013.1 μmol h−1 g−1, which were 19.6 and 6.6 times higher than pure g-C3N4, respectively. The ZrO2 nanoparticles (ZNps) prepared via freeze-drying, but without polymer precursor, were used as support to form ZrO2/g-C3N4 nanoparticles (ZCNps-2) for comparison study. The RhB degradation rate and H2 evolution rate of the 3DP/ZC-2 under visible light were about 3.7 and 5.3 times higher than ZCNps-2. Their enhanced photocatalytic activity could be attributed to their unique 3D heterointerface with matched energy bands for rapid charge separation and transfer and a hierarchical porous structure for mass transfer and surface reaction processes. The scavenger trapping and ESR measurements confirmed that the primary reactive radicals for degradation were superoxide radical ions (⋅O2−), hydroxyl radicals (⋅OH), and photogenerated holes (h+). The pH-dependent photocatalytic degradation activity originated from the H+-related ⋅OH conversion reaction. Besides, the macro self-supporting nature could provide excellent separability and recyclability, and self-supporting membranes were also constructed and demonstrated as stable and recyclable photocatalysts. This work provides a new routine for designing 3D-heterojunctions as new kinds of functional materials for applications in environmental remediation and green energy production.

Thermodynamic Study of H2-FeO Based on the Principle of Minimum Gibbs Free Energy

Studies have shown that the reduction of wustite is the limiting factor in the ironmaking process, whether in hydrogen-based shaft furnaces, hydrogen-rich blast furnaces or smelting reduction vessels. The study of the thermodynamic conditions for the reduction of molten wustite by hydrogen is of great significance for the optimization of the ironmaking process, energy saving and emission reduction. Previous studies have mostly focused on the thermodynamic study of the reduction at a lower temperature, but the data at high temperatures are different, which makes the calculation of thermodynamics difficult. Moreover, it is difficult to obtain experimental evidence for the data at high temperature, so calculation is needed to verify its feasibility. In this paper, a thermodynamic calculation model for the reduction of molten wustite by hydrogen based on the principle of minimum Gibbs free energy is developed. The enthalpy changes of the reaction at different temperatures and the partial pressure of hydrogen required for the reaction to occur are calculated, and the energy change during the reaction is analyzed. The results show that the partial pressure of hydrogen for the reduction of molten wustite by hydrogen at high temperatures decreases from 0.67 at 1650 K to about 0.65 at 2000 K. The enthalpy changes of reaction at 1873 K are only 1/4 to 1/3 of that at 1173 K compared with that at the corresponding temperature between hydrogen for the reduction of molten wustite (1873 K) and hydrogen-based shaft furnace reaction (1173 K). Interestingly, the thermodynamic calculations show that the effect of energy absorption in the gas–liquid reaction of hydrogen with wustite at high temperatures is much lower than in the gas–solid reaction zone at low temperatures. These results indicate that the energy change of the reduction of molten wustite by hydrogen at high temperatures is better than that of hydrogen reduction at low temperatures, and the thermodynamic conditions are more favorable, with slightly different results from different thermodynamic databases, but the general trend is the same. The results of this study will provide fundamental data to support new hydrogen metallurgy technologies in the future. If its correctness can be verified experimentally in the future, this result will be promoted to the development of a new alternative ironmaking technology, hydrogen-based smelting reduction.

Carbon-induced magnetic properties and anomalous Hall effect in Co2Mn2C thin films with L10 -like structures

${\mathrm{Co}}_{2}{\mathrm{Mn}}_{2}\mathrm{C}$ thin films were synthesized via vacuum carburization of the host CoMn alloy films based on a conventional gas-solid reaction to demonstrate the effect of C, a common light element, on the magnetic and spintronic materials. The crystal structure transitioned from the disordered face-centered-cubic CoMn to the $L{1}_{0}$-like ${\mathrm{Co}}_{2}{\mathrm{Mn}}_{2}\mathrm{C}$, for which the lattice constant increased from 0.356 to 0.378 nm. The C $1s$ x-ray photoemission spectra of the ${\mathrm{Co}}_{2}{\mathrm{Mn}}_{2}\mathrm{C}$ film indicated hybridization in C-Co and C-Mn and a homogeneous concentration of C in the film. The enhancement of both the saturation magnetization and the anomalous Hall conductivity (${\ensuremath{\sigma}}_{xy}$) was induced by C, attributing to the magnetic transition to the ferrimagnetic spin order. The surface flatness and high ${\ensuremath{\sigma}}_{xy}$ are promising characteristics for spintronic applications such as the spin-anomalous Hall effect. The atom- and spin-resolved density of states (DOS) via first-principles calculations revealed that face-centered Mn(II) and Co could be significantly influenced by C because of p-d hybridization, resulting in enhanced spin polarization of the DOS at the Fermi level of \ensuremath{\sim}0.82. These results demonstrate that the use of C could be an essential way to boost material properties in the future.

Mechanism of Reductive Fluorination by PTFE-Decomposition Fluorocarbon Gases for WO3

Reductive fluorination, which entails the substitution of O2- from oxide compounds with F- from fluoropolymers, is considered a practical approach for preparing transition-metal oxyfluorides. However, the current understanding of the fundamental reaction paths remains limited due to the analytical complexities posed by high-temperature reactions in glassware. Therefore, to expand this knowledgebase, this study investigates the reaction mechanisms behind the reductive fluorination of WO3 using polytetrafluoroethylene (PTFE) in an Ni reactor. Here, we explore varied reaction conditions (temperature, duration, and F/W ratio) to suppress the formation of carbon byproducts, minimize the dissipation of fluorine-containing tungsten (VI) compounds, and achieve a high fluorine content. The gas-solid reaction paths are analyzed using infrared spectroscopy, which revealed tetrafluoroethylene (C2F4), hexafluoropropene (C3F6), and iso-octafluoroisobutene (i-C4F8) to be the reactive components in the PTFE-decomposition gas during the reactions with WO3 at 500 °C. CO2 and CO are further identified as gaseous byproducts of the reaction evincing that the reaction is prompted by difluorocarbene (:CF2) formed after the cleavage of C═C bonds in i-C4F8, C3F6, and C2F4 upon contact with the WO3 surface. The solid-solid reaction path is established through a reaction between WO3 and WO3-xFx where solid-state diffusion of O2- and F- is discerned at 500 °C.

Mechanistic Insights into Molecular Crystalline Organometallic Heterogeneous Catalysis through Parahydrogen-Based Nuclear Magnetic Resonance Studies.

The heterogeneous solid-gas reactions of crystals of [Rh(L2)(propene)][BArF4] (1, L2 = tBu2PCH2CH2PtBu2) with H2 and propene, 1-butene, propyne, or 1-butyne are explored by gas-phase nuclear magnetic resonance (NMR) spectroscopy under batch conditions at 25 °C. The temporal evolution of the resulting parahydrogen-induced polarization (PHIP) effects measures catalytic flux and thus interrogates the efficiency of catalytic pairwise para-H2 transfer, speciation changes in the crystalline catalyst at the molecular level, and allows for high-quality single-scan 1H, 13C NMR gas-phase spectra for the products to be obtained, as well as 2D-measurements. Complex 1 reacts with H2 to form dimeric [Rh(L2)(H)(μ-H)]2[BArF4]2 (4), as probed using EXAFS; meanwhile, a single-crystal of 1 equilibrates NMR silent para-H2 with its NMR active ortho isomer, contemporaneously converting into 4, and 1 and 4 each convert para-H2 into ortho-H2 at different rates. Hydrogenation of propene using 1 and para-H2 results in very high initial polarization levels in propane (>85%). Strong PHIP was also detected in the hydrogenation products of 1-butene, propyne, and 1-butyne. With propyne, a competing cyclotrimerization deactivation process occurs to afford [Rh(tBu2PCH2CH2PtBu2)(1,3,4-Me3C6H3)][BArF4], while with 1-butyne, rapid isomerization of 1-butyne occurs to give a butadiene complex, which then reacts with H2 more slowly to form catalytically active 4. Surprisingly, the high PHIP hydrogenation efficiencies allow hyperpolarization effects to be seen when H2 is taken directly from a regular cylinder at 25 °C. Finally, changing the chelating phosphine to Cy2PCH2CH2PCy2 results in initial high polarization efficiencies for propene hydrogenation, but rapid quenching of the catalyst competes to form the zwitterion [Rh(Cy2PCH2CH2PCy2){η6-(CF3)2(C6H3)}BArF3].

High energy-density and power-density cold storage enabled by sorption thermal battery based on liquid-gas phase change process

Cold storage is essential for the preservation of food/medical goods, energy-saving of air conditioning, and emergency cooling. However, conventional cold storage in the form of sensible heat or solid-liquid latent heat suffers from the low energy density and large cold loss during long-term storage. To address the problem, a scalable sorption thermal battery (STB) with storage capacity of 30 kWh is designed and fabricated for realizing high energy-density and power-density cold storage by proposing sorption-induced liquid-gas phase change strategy. The STB utilizes the bonding energy of sorption working pair of zeolite 13X-water to achieve cold storage during charging phase, and utilizes the liquid-gas evaporation heat of water to realize cold production during discharging phase. The cold-storage performance of the STB prototype during charging/discharging processes is experimentally investigated at different operating conditions. By optimizing the assembled structure of solid-gas reactor and enhancing the heat transfer performance of liquid-gas evaporator, the STB exhibits high cold energy density up to 114.92 Wh/kg and 26.76 kWh/m3, and high power density of 455.62 W/kg and 106.10 kW/m3, over the conventional cold storage technologies. Correspondingly, the STB demonstrates a good performance in thermal management of data centers with cooling power as high as 150 kW. Moreover, the STB has the distinct advantage of near-zero cold energy loss in long-term cold storage. The proposed scalable sorption thermal battery based on sorption-induced liquid-gas evaporation heat of liquid offers a promising route to realize high energy density cold storage.

Enhancement of low-temperature solid oxide fuel cell performance and durability via surface chemistry modification

The development of active cathodes is one of the most critical challenges to lowering the operating temperature for solid oxide fuel cells (SOFCs). Here we demonstrated that by modifying the cathode surface chemistry at a relatively low temperature, the cathode activity and durability can be simultaneously enhanced on high-performing, low-temperature cathodes such as (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) and Sr0.5Sm0.5CoO3-δ (SSC). This low-temperature modification using multi-valent cations activates the highly defected surface and maintains the nanoscale electrocatalysts by bypassing the high-temperature sintering procedure for SOFC fabrication. The modified cathode at 600°C shows an order of magnitude reduction in impedance to only 0.05 Ωcm2 with a peak power density of 1.1 W/cm2 and increases stability over 2000 h. The combination of in situ characterization, distribution of relaxation time analysis on impedance spectroscopy, and surface chemistry analysis reveals the importance of surface chemistry control on the gas-solid reaction activity and durability and provides the design principle for numerous future solid oxide cells.

Thermo-economic assessment of salt hydrate-based thermochemical heat transformer system: Heat upgrade for matching domestic hot water production

Efficient energy storage technology is a crucial step in achieving the broad deployment of renewable energies. Thermochemical heat transformer (THT), which rely on reversible gas–solid reactions, can provide an option for efficient energy storage and heat upgrade. In this article, a pressurisation-assisted sorption THT system driven by low-grade solar thermal energy is proposed to meet the heat demand of domestic hot water (DHW) production, and different temperature rises can be realised by regulating the water vapour pressure. The thermodynamic and economic performances of the THT systems employing ten kinds of salt hydrates are investigated under various operating conditions. The results indicate that most salts-based THT systems enable output temperatures higher than 60 °C. Two-stage pressurisation systems can further elevate the temperature lift but at the cost of thermodynamic performance. SrBr2·6H2O, K2CO3·1.5H2O, and LiOH·H2O are more promising hydrates for the THT system by taking energy density, temperature lift, and thermo-economic performance into account. Compared to the classical TCES cycle, the temperature lifts attained by the above salts-based single-stage and two-stage pressurisation THT systems are 17.6–19.9 °C and 32.2–37.8 °C, respectively. Multi-objective optimisation results suggest that the optimum exergy efficiency for the SrBr2-, K2CO3-, and LiOH-based systems are 82.47%, 55.08%, and 63.97%, and the corresponding levelized energy costs (LECs) are 0.3549, 0.7132, and 0.5721 $/kWh, respectively. The results of this study demonstrate the significant potential of developing such pressurisation-assisted THT system for heat upgradation targeting DHW production.

CFD-DEM study of reactive gas-solid flows with cohesive particles in a high temperature polymerization fluidized bed

The cohesive particles are commonly encountered in high temperature polymerization fluidized bed reactors. However, detailed studies on the effect of cohesiveness on the hydrodynamics, heat transfer, and reaction characteristics in such reactors have been rarely reported. In this work, a CFD-DEM approach coupled with solid bridge force model and polymerization reaction kinetics model is established to simulate the reactive gas–solid flows with cohesive particles. The results demonstrate that cohesive particle agglomeration significantly increases the inhomogeneity of concentration and velocity fields, and hinders particle circulation. The hindered particle circulation further results in pronounced temperature inhomogeneity. Moreover, the local hot spots are readily formed in the agglomerates, which expand and deteriorate rapidly if not controlled promptly. Besides, how the cohesion model parameters, namely contact time and maximum cohesive force limitation, affect the onset temperature and the severity of particle agglomeration is revealed. The established model extends the particle-scale study of cohesive gas–solid flows to reactive systems.

Interfacial construction of P25/Bi2WO6 composites for selective CO2 photoreduction to CO in gas-solid reactions.

Photocatalysis provides an attractive approach to convert CO2 into valuable fuels, which relies on a well-designed photocatalyst with good selectivity and high CO2 reduction ability. Herein, a series of P25/Bi2WO6 nanocomposites were synthesized by a simple one-step in situ hydrothermal method. The formation of a heterojunction between Bi2WO6, which absorbs visible light, and P25, which absorbs ultraviolet light, expands the utilization of sunlight by the catalysts, and consequently, leads to a remarkably enhanced CO2 selective photoreduction to CO. The maximum CO yield of the P25/Bi2WO6 heterojunction under simulated solar irradiation was 15.815 μmol g-1 h-1, which was 4.04 and 2.80 times higher than that of pure P25 and Bi2WO6, respectively. Our investigations verified a Z-scheme charge migration mechanism based on various characterization techniques between P25 and Bi2WO6. Furthermore, in situ DRIFTS uncovered the related reaction intermediates and CO2 photoreduction mechanism. Our work sheds light on investigating the efficacious construction of Bi2WO6-based hybrids for light-driven photocatalysis.

Synthesis of ultrafine (Mo,W)Si2 composite powders from high purity molybdenum concentrate

(Mo,W)Si2 composite powders with the grain size of about 1 ?m were synthesized at 1150? for 2 h. The high purity molybdenum concentrate (with the main component of MoS2), W and Si powders were utilized as raw materials and lime as desulfurizer. The graphite felt was laid between the compact (made of MoS2, W and Si) and the lime to facilitate the separation of the produced composite powders from desulfurization product. The phase composition, microstructure evolution, and residual sulfur content during the silicothermic reduction reaction were evaluated. The experimental results showed that the reaction could be completed after a reaction time of 1150? for 2 h, and the residual sulfur content of the product was 0.087 wt.%. It was concluded that the interactions between Si and the intermediate products of SiS and SiS2 are crucial for the preparationof (Mo,W)Si2 composite powders at low temperatures. The preparation process could be divided into three stages: solid state reactions between MoS2, W and Si to produce MoSi2, WSi2 and gaseous SiS; gas-solid reaction between MoS2, W and gaseous SiS to generate MoSi2, WSi2 and gaseous SiS2; and gas-solid reaction between gaseous SiS2 and Si to form SiS gas. With this short flow process, fine-grained (Mo,W)Si2 composite powders can be produced at low cost at low temperature, which has great application potential.

Spontaneous gas–solid reaction on sulfide electrolytes for high-performance all-solid-state batteries

Sulfide solid electrolytes modified by CO2/O2 deliver enhanced moisture resistance and superior cathodic interfacial stability.

In crystallo lattice adaptivity triggered by solid-gas reactions of cationic group 7 pincer complexes.

The group 7 complexes [M(κ3-2,6-(R2PO)2C5H3N)(CO)2L][BArF4] [M = Mn, R = iPr, L = THF; M = Re, R = tBu, L = vacant site] undergo in crystallo solid-gas reactivity with CO to form the products of THF substitution or CO addition respectively. There is a large, local, adaptive change of [BArF4] anions for M = Mn, whereas for M = Re the changes are smaller and also remote to the site of reactivity.

Enhancing the durability of Au clusters in CO2 photoreduction via encapsulation in Cu-based metal-organic frameworks.

Here, we report the encapsulation of Au25 nanoclusters in a Cu3(BTC)2 metal-organic framework (Au25@Cu-BTC), which can achieve CO2 photoreduction for selective CO production in a gas-solid reaction system at low-concentration CO2 atmospheres (even to 0.1%), with remarkably enhanced durability up to at least 48 h.