Efficient Utilization Of Solar Energy Research Articles

Photothermally accelerated photocatalysis over hollow carbon@ZnIn2S4 for enhanced amine oxidation

Efficient solar energy utilization has attracted increasing interest in the past few decades.

Aerosol-based deposition of broadband antireflective silica coating with closed mesoporous structure

Solar energy will be a crucial part of the sustainable, fossil free energy production of the future. A majority of this will be produced by solar collectors and photovoltaics. Important for the efficient utilization of the incident solar energy for both technologies are a cover glass with antireflective coatings giving it a high solar transmittance. In the current paper we describe the development of antireflective mesoporous silica coatings on low-iron float glass using the aerosol-based nFOG™ deposition technique. The coatings exhibit a hexagonal and closed pore structure, high smoothness, superhydrophilic properties (contact angle <5°) and consistent thicknesses of approximately 110 nm. This is in line with optimal thickness determined from simulations of the antireflective behavior. Low-iron float glass coated on both sides show a highly reproducible solar weighted transmittance of 95% in the wavelength range 300–2500 nm and an antireflective effect increasing with incident angle. The smoothness, closed pores and low contact angle indicate a high cleanability, which in combination with the high transmittance render a competitive broadband antireflective coating well adapted for solar glass applications. • Sol-gel synthesis of antireflective silica coatings based on evaporation induced self-assembly using the aerosol-based nFOG™ technique. • Mesoporous coatings exhibiting hexagonally ordered pores, aligned parallel to the substrate, but closed to the surface. • Smooth, consistent, 110 nm thick coatings were produced, which is close to the simulated optimal thickness of 120 nm. • Low-iron float glass with the antireflective coating exhibit a solar weighted transmittance of 95%.

Optimizing solar energy utilization and energy efficiency through thermal energy storage with phase change materials in a solar water heating system

Solar energy (SE) is non-polluting and sustainable. However, the strength of the sun’s rays shifts as the seasons change, the weather shifts, and the day and night cycles. It is possible to store energy as heat, which can then be used for a variety of applications in the future. The primary objective of this research was to extend the time that high water temperature (HWT) was maintained by using phase change materials (PCM) to reduce energy consumption. To test the efficacy of an FPSWHS using 18 % (63 kg) of PCM condensed paraffin wax of type RT42, an experimental rig was constructed. To further expand PCM surface area and speed up charging and discharging, 18 aluminium cylinders were employed. Given the varying weather patterns in the India, this research was also useful in settling on a suitable PCM for SWHS. At 60°C input temperature of water (Tin) and 0.11 kg.s-1 flow rate of mass in water (mw), including RT42 into a water-PCM storage tank reduced power consumption by as much as 5.75 kWh, for a total system energy consumption of 31.4 kWh. The results showed a 27 % drop in daily average carbon footprint and a 27 % increase in overall system efficiency.

Solar-light-sensitive Zr/Cu-(H2BDC-BPD) metal organic framework for photocatalytic dye degradation and hydrogen evolution

Efficient solar-energy utilization is the future technology to address energy and environmental issues. In this study, we have prepared Zr/Cu based MOF for the mineralization of pollutants and hydrogen evolution from water. The photocatalytic synergism of the prepared Zr/Cu MOF has been investigated from light-controlled studies. Optimized Zr composition has enhanced photocatalytic degradation efficiencies. The present research aims to synthesize novel Zr/Cu-metal based metal organic frameworks (MOFs) by solvothermal (ST) methods and evaluate their photoluminescence (PL) property and photo catalytic activity. Herein, we demonstrate the preparation of tailor-made MOF with solar light sensitive and stable features. The optimized catalyst has shown 94.8% efficiency against the degradation of methylene blue and showed a hydrogen generation performance of 12.5 mmolg−1h−1. It was noticed that, concentration of Zr has profound influence on the photocatalysis. Systematic investigation proved that, catalyst has high surface area, metal-organic architecture for improved photocatalytic performance. Further, excellent chemical stability of catalyst after many cycles of reuse would make Zr/Cu-(H2BDC-BPD) a robust photo-active material.

An efficient and universal solar interfacial photothermal reactor toward liquid phase oxidation

AbstractPhotothermal catalysis has attracted great attention owing to high solar energy utilization efficiency, and great progress has been achieved in gas‐phase catalysis. However, photothermal catalysis in liquid‐phase shows a limited performance, due to high specific heat capacity of liquid. Herein, an interfacial photothermal catalytic (IPC) strategy applying an IPC leaf was designed for liquid‐phase catalysis using benzyl alcohol oxidation as the model reaction. On even ground, the benzaldehyde generation rate (8.7 mmol gcat−1 h−1) of the IPC system with Ce‐doped MnO2 as photothermal catalyst was almost 4.8 times and 3 times of bulk photothermal catalysis and the relative bulk thermal catalysis. Experimental results proved that this excellent catalytic performance could be attributed to both the high temperature achieved and the enhanced lattice oxygen activity by solar irradiation. This IPC system also exhibited good universality and long‐term durability. Our work innovatively created a green strategy to obtain fine chemicals with only solar irradiation.

Unveiling the role of metallic CoP@Ni2P sea-urchin-like nanojunction as a photothermal cocatalyst for enhancing the H2 generation and benzaldehyde formation over CdZnS nanoparticles

Aiming to develop a photocatalyst that can simultaneously produce valuable chemicals and clean H2 fuel for promoting the utilization efficiency of solar energy, herein, a sea-urchin-like CoP@Ni2P binary nanojunction was employed as an efficient photothermal cocatalyst to couple with zero-dimensional CdZnS (CZS) solid solution for achieving superior coordinative redox reaction. The CoP@Ni2P/CZS hybrid displayed a high solar-driven H2 generation rate of 40.92 mmol g–1 h–1 coupling with a benzaldehyde formation rate of 20.33 mmol g–1 h–1, which was 16.4 and 8.0 times higher than that of bare CZS. Furthermore, the CoP@Ni2P/CZS hybrid also achieved a high photothermal H2 production under a broad light range from 420 to 720 nm, and the H2 production reached 44.48 µmol g–1 h–1 under the 720 nm light illumination. The enhanced catalytic performance can be ascribed to that the CoP@Ni2P nanojunction with photothermal effect can speed up the separation and transport of carriers, offer more catalytic active sites, and induce an increase in temperature to optimize reaction kinetics. This study may open a facile route to design novel binary metal phosphides with dual functions in photocatalysis for the full exploitation of solar energy.

Broadband and strong visible-light-absorbing cuprous sensitizers for boosting photosynthesis

Rational construction of broadband and strong visible-light-absorbing (BSVLA) earth-abundant complexes is of great importance for efficient and sustainable solar energy utilization. Herein, we explore a universal Cu(I) center to couple with multiplestrong visible-light-absorbing antennas to break the energy level limitations of the current noble-metal complexes, resulting in the BSVLA nonprecious complex (Cu-3). Systematic investigations demonstrate that double "ping-pong" energy-transfer processes in Cu-3 involving resonance energy transfer and Dexter mechanism enable a BSVLA between 430 and 620 nm and an antenna-localized long-lived triplet state for efficient intermolecular electron/energy transfer. Impressively, Cu-3 exhibited an outstanding performance for both energy- and electron-transfer reactions. Pseudo-first-order rate constant of photooxidation of 1,5-dihydroxynaphthalene with Cu-3 can achieve a record value of 190.8 × 10-3 min-1 among the molecular catalytic systems, over 30 times higher than that with a noble-metal photosensitizer (PS) [Ru(bpy)3]2+. These findings pave the way to develop BSVLA earth-abundant PSs for boosting photosynthesis.

Stannous Tungstate Semiconductor for Photocatalytic Degradation and Photoelectrochemical Water Splitting: A Review

The use of photocatalysis and photoelectrocatalysis is expected to achieve the efficient utilization of solar energy to alleviate and even solve the problems of energy depletion and environmental pfollution. At present, stannous tungstate materials have attracted extensive attention in the fields of photocatalysis and photoelectrocatalysis as favorable candidates for such utilization because of their narrow band gap energy (which is ~1.7 eV for the α phase and ~2.7 eV for the β phase, respectively) and unique band structure (which covers the oxidation and reduction potential of water). However, their practical application is still limited by excessive electron–hole recombination and poor stability. In this review, basic information (crystal and electronic structures) related to photocatalysis and photoelectrocatalysis is presented. Additionally, various strategies to enhance the photocatalytic and photoelectrochemical properties of stannous tungstate materials, such as morphological modification, crystal facet engineering, doping modification, and multicomponent compositing, are summarized. Furthermore, the achievements and difficulties of the relevant studies are discussed. The information presented in this review can provide a reference for subsequent research on the photocatalytic and photoelectrochemical performance of tungstate-based materials.

Recent Advances in Ternary Metal Oxides Modified by N Atom for Photocatalysis

Ternary metal oxides (TMOs) with flexible band structures are of significant potential in the field of photocatalysis. The efficient utilization of renewable and green solar energy is of great importance to developing photocatalysts. To date, a wide range of TMOs systems has been developed as photocatalysts for water and air purification, but their practical applications in visible light-assisted chemical reactions are hindered mainly by its poor visible light absorption capacity. Introduction of N atoms into TMOs can narrow the band-gap energy to a lower value, enhance the absorption of visible light and suppress the recombination rate of photogenerated electrons and holes, thus improving the photocatalytic performance. This review summarizes the recent research on N-modified TMOs, including the influence of N doping amounts, N doping sites, and N-induced phase transformation. The introduced N greatly tuned the optical properties, electronic structure, and photocatalytic activity of the TMOs. The optimal N concentration and the influence of N doping sites are investigated. The substitutional N and interstitial N contributed differently to the band gap and electron transport. The introduced N can tune the vacancies in TMOs due to the charge compensation, which is vital for inducing different activity and selectivity. The topochemical ammonolysis process can convert TMOs to oxynitride with visible light absorption. By altering the band structures, these oxynitride materials showed enhanced photocatalytic activity. This review provides an overview of recent advances in N-doped TMOs and oxynitrides derived from TMOs as photocatalysts for environmental applications, as well as some relevant pointers for future burgeoning research development.

Efficient use of solar energy

This paper is mainly about the use of solar energy in life to make a summary, and how to improve the utilization of these aspects to make suggestions. Sunlight transmits electricity to the earth all the time. If the total radiation power from sunlight to the earth is converted into power generation power, it can reach 1.77× kW, which is several hundred million times larger than the current global per capita consumption of electricity. There are not only a lot of sunlight, but also all green energy sources from sunlight, such as wind energy, tidal energy, microbial energy, hydraulic energy, etc., all belong to renewable energy sources. As long as there is sunlight, renewable energy sources are as constant as sunlight. In the process of the efficient development and utilization of solar energy, the photovoltaic utilization of nuclear energy has become the fastest progress around the whole world in recent years, the most vitality of the scientific research field.

One step reactive ion etching of black germanium conical nanostructures: Ultra-wide solar spectral absorption, finite element simulation, super hydrophilicity, photothermal conversion

We report a reactive ion etching process based on SF 6 –CHF 3 , which can prepare black germanium at low RF power and normal temperature. The absorption of black germanium in the spectral range of 300–1750 nm is greater than 99%. Spectral selectivity optimization allows nano tapered germanium to absorb nearly 98.1% of solar radiation. This nanostructure is uniform in a large area and also supports patterning design for the application in related fields such as photothermal imaging. Here, we discuss the effect of SF 6 and CHF 3 plasma concentrations on the progress of chemical reactions on the germanium surface and their essential role in forming tapered nanostructures. We observe its surface plasmon resonance by finite-difference time-domain way. Finally evaluate its feasibility in devices by photothermal conversion and water droplet evaporation experiments. The proposal of this work provides an available method for semiconductor micromachining, and also provides experimental and theoretical support for the efficient thermal utilization of solar energy. In conclusion, we analyzed the mechanism of one-step etching of highly absorbing tapered nanostructures by SF 6 –CHF 3 -based RIE process by SEM and XPS. The germanium surface tends to form particles at the initial stage of etching, and due to the very high concentration of negative ions in the SF 6 plasma, these particles gradually form GeS x clusters. The germanium fluoride is mainly present at the surface of the germanium sample, while the germanium sulfide extends to a greater depth, so these clusters are not effective in preventing etching. The CHF 3 plasma greatly reduces the negative ion concentration and reduces the tendency of particle formation in favor of smoother GeS x and C x H z F y layers, which are very favorable for the formation of nanostructures. Aggregation of the germanium sidewalls decreases with depth, so tapered nanostructures are gradually formed with etch time. In addition, over-etching leads to additional carbon deposition, which is mainly composed of fluorocarbon polymers (C x H y F z ) formed from the decomposition products of CHF 3 . The wide spatial distribution of the sizes of the tapered nanostructures makes the absorptivity of black germanium more than 99% in the 300–1750 nm spectral range. As an indirect bandgap semiconductor, the absorption of photons makes electrons excited from the valence band to the conduction band with a great probability of releasing energy to the lattice, converting it into phonons, and turning it into heat energy. The cone-shaped nanostructured germanium can be heated to 69.4 °C in 20 min, and the heating rate can reach 7.98 °C/min in 300 s. The conical nanostructure modification makes germanium exhibit superhydrophilicity, and the water droplets make wet contact with germanium and fill the grooves on the surface of the nanostructures, making it capable of completely evaporating 0.05 ml droplets within 101 s. It is very competitive in heating and evaporation of water droplets.a) Black germanium photos, and SEM images of nano cones; b) Comparison of absorptivity between black germanium and polished germanium; c) Infrared image of graphic germanium wafer; (the letter part is nano cone structure, and the rest is polished germanium) d) With the increase of etching time, the temperature change curve of the sample under simulated sunlight irradiation (1 solar intensity). • Disordered nanocrystalline germanium was prepared by metal induced one-step self masked RIE. • The absorbance in the 300-1750 nm regions was higher than 98%. • The structure has excellent optical properties due to light trapping effect and plasma resonance. • The excellent optical properties and super hydrophilic properties make the structure have excellent photothermal properties.

Novel core–shell heterojunction photocatalytic wire mesh for efficient ciprofloxacin degradation under visible light

In order to solve the problems of easy recombination of electron–hole pairs, low solar energy utilization efficiency and difficult reuse of catalyst, a core–shell α–Fe2O3/Bi2MoO6@304SS heterojunction photocatalytic was synthesized and successfully immobilized on the 304 stainless steel (304SS) wire mesh. The result featured a flower–like particles assembled by a nanosheet catalyst uniformly distributed on the surface of the α–Fe2O3 shell, and showed high adsorption and visible–light photocatalytic activity towards ciprofloxacin (CIP). The CIP degradation efficiencies of 96 % and 92 % in the presence of visible light from a 40 W LED lamp and direct sunlight, respectively. Moreover, the photocatalytic mesh exhibited good structure stability and recycling performance. As determined, a built–in the electric field generated by the heterojunction reduced the recombination probability of electron–hole pairs, and significantly improved photocatalytic activity. Additionally, the possible electron migration mode in the heterojunction interface is proposed, the photocatalytic mechanism is elucidated, and possible degradation pathways of CIP are analyzed. With these unique features, the synthesis of photocatalytic mesh could be easily applied in water environment restoration and wastewater treatment systems.

Performance analysis of a novel combined cooling, heating and power system with solar energy spectral beam splitting

The solar energy spectrum absorbed and converted by PV modules is mainly located in the high-frequency band (380–1200 nm), while the spectral energy in other bands that fail to generate electricity is converted to heat and dissipated into the environment, which leads to lower energy utilization efficiency. Spectral beam splitting cascade utilization is a potential technology to improve the efficiency of solar energy utilization. In this paper, a novel combined cooling, heating and power system with solar energy spectral beam splitting was developed according to matching the energy grade and the operating characteristics of refrigeration cycles. The theoretical investigation carried the parameters distribution of energy load and efficiency out. The solar spectrum is divided into the high-frequency spectrum for electric power generation and the low-frequency spectrum for thermal energy harvesting. The spectrum energy after removing electrical power generation is recovered for fluid heating. The part of thermal energy with high temperature is used to drive the ejector refrigeration system to obtain the cooling capacity. Hot water is derived from low temperature thermal energy. Through the effective conversion of energy and heat recovery, the novel system ensures the efficiency of solar energy utilization and realizes a high-efficiency combined supply of cooling, heating and electricity. The total energy utilization efficiency and the total converted generation efficiency of the novel system can reach 82.7 % and 44.9 %, respectively, which is a remarkable improvement from 30.7 % of the conventional single photovoltaic system. The research results provide inspiration for the efficient utilization of solar energy and facilitate the realization of more application scenarios.

Solar application potential and thermal property optimization of a novel zero-carbon heating building

Building Integrated Heat Pipes (BIHP), specifically a novel passive solar house integrated with gravity heat pipes, realizes envelopes with variable thermal properties and makes effective and efficient use of solar energy to reach zero-carbon heating, and can greatly improve the indoor thermal environment in winter. In this paper, an efficient method based on particle swarm optimization for the optimization of thermal properties of the BIHP interior envelope is proposed. The key thermal properties of the heat pipe and the exterior and interior envelopes are optimized, and the solar application potential of improving indoor thermal discomfort by BIHP in five representative cities of northern China is obtained. The results show that the equivalent thermal conductivity of the heat pipe is suggested to be greater than 2 × 104 W/(m·K). The optimal BIHP should have exterior envelopes with high thermal resistance and interior envelopes with large thermal capacity. In the selected areas, the optimal BIHP improves indoor thermal discomfort by 36 %–100 % and increases the minimum indoor operative temperature by 5.1–10.5 °C compared to the reference building. BIHP is recommended in areas with the ratio of radiation to temperature difference greater than 5 W/(m2·K) and can reach zero-carbon heating in Lhasa and Yinchuan. This research provides a global matching and optimization method for the effective and efficient utilization of solar energy to reach zero-carbon heating and evaluates the application potential of BIHP.

High thermal storage ability and photothermal conversion capacity phase change capsule with graphene oxide covalently grafted silica shell

Preparation of phase change materials with energy collection, conversion and storage functions is considered to be an important way to solve the energy shortage problem. Hence, a novel phase change capsule (EP@MGO) with photothermal conversion function was innovatively designed. In the process of preparing EP@MGO, the modified graphene oxide (MGO) layer was covalently anchored on the surface of the phase change capsule encapsulated by silica shell (EP) through Si-O-Si bonds, in which MGO was obtained by modifying GO nanosheets with isocyanate propyl triethoxysilane. The as-prepared EP@MGO microcapsule presents favorable latent heat storage capacity, with enthalpy of 139.8 J/g and high encapsulation efficiency of 83.6%. Besides, the thermal stability, leakage-proof property, durability, and thermal reliability of EP@MGO were enhanced significantly due to the physical protection effect provided by the SiO2-MGO double-layer shell. Moreover, the covalently MGO-grafted silica shell endows EP@MGO with high thermal conductivity (1.603 W/m·K), which improves its thermal management efficiency. More importantly, EP@MGO exhibits the potential ability to effectively utilize ultraviolet and visible light. In detail, the absorbance of EP@MGO increased by ∼192% in the ultraviolet and visible light region (200–800 nm), and the photothermal conversion efficiency under near infrared (NIR) region as high as 64.4%, which has negligible change (64.2%) even after 50 times heating-cooling cycle. Therefore, the phase change capsule EP@MGO provides a new idea for realizing efficient utilization of solar energy, and exhibits the application potential in biomedical treatment, smart textiles, and solar thermal collector.

Biomimetic platinum forest enables 3D micro-supercapacitors with enhanced areal performance

Nowadays, the rapid development of portable micro-electronics has stimulated a significantly increasing demand in micro-supercapacitors (MSCs) for efficient micropower sources. However, the performance of MSCs is hindered by the dense electrode design with sluggish ion diffusion or reaction kinetics and tortuous charge transfer pathways, especially at high mass loading. Inspired by the structure of natural forest with efficient solar energy utilization, we fabricate an innovative biomimetic Pt forest (named forest-like Pt) as a robust three-dimensional (3D) conductive current collector by a simple one-step electrodeposition process. This hierarchical nanoarchitecture significantly improves the exposed surface areas of active electrode materials. As a proof-of-concept, 3D MSCs based on poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer grown on such forest-like Pt exhibit an enhanced areal capacitance of 69.3 mF cm−2 at 0.1 mA cm−2, which is more than 5-fold larger than that of pristine PEDOT-based MSCs using conventional flat Au current collectors. Furthermore, the assembled 3D MSCs show a high areal energy density (6.16 μW h cm−2) and outstanding rate capability (63.2 mF cm−2 even at 5 mA cm−2). Thus, this novel design concept provides a new approach to build advanced electrode nanoarchitectures for the next-generation MSCs.

Balanced broad learning prediction model for carbon emissions of integrated energy systems considering distributed ground source heat pump heat storage systems and carbon capture & storage

With the development of social industry, numerous carbon emissions have led to global warming and caused a huge negative impact on the environment. Carbon neutrality has been proposed to solve this problem; one of the primary issues in achieving carbon neutrality in integrated energy systems is to reduce carbon emissions. This paper utilizes distributed ground source heat pump heat storage systems in integrated energy systems to simultaneously improve the utilization efficiency of wind energy and solar energy for the first time. Moreover, the carbon capture and storage technology in integrated energy systems is considered to store excess CO2 in geological layer. Energy storage in integrated energy systems is applied to adjust the energy network balance. Finally, a balanced broad learning prediction model considering various heterogeneous data is established for load forecasting with 96.12% prediction accuracy. In four cases of the lower or higher wind and solar energy generation curves, carbon emissions are reduced to 82.02% of the original at least.

A study on a novel solar contribution evaluation method for the solar-aided coal-fired power generation system

Solar-aided coal-fired power generation (SACPG) technology is an effective method of solar energy utilization. It could balance the demand of carbon dioxide emission reduction and renewable energy efficient power generation and promote carbon peaking and carbon neutralization. Accurate analysis of the share of solar energy in the unit output power could benefit the selection of the best integration scheme and exploitation of solar energy for further research. A novel solar contribution evaluation method of an SACPG system is put forward. The exergy is taken as the evaluation benchmark, and the method can be applied in an SACPG system with multiple integration positions with solar energy. The solar energy input from different positions in the system is analyzed separately. The solar energy input positions and the impact of solar exergy destruction on the solar energy contribution are considered. The proposed method also analyzes the flow direction and destruction of each solar exergy in different parts of the SACPG system and expresses the solar contribution in the electricity generated by each stage steam turbine in the form of a theoretical formula. Ultimately, the solar exergy contribution in the whole SACPG system is calculated by accumulating each result. Furthermore, the new method is applied to a tower solar-aided coal-fired power generation (TSACPG) system with thermal energy storage (TES) for comparative analysis. Compared with other solar contribution evaluation methods, the comprehensiveness and accuracy of the novel method are analyzed. Meanwhile, the exergy destruction distributions of the TSACPG system are revealed. The method can also be further used to excavate the application potential of solar energy in coal-fired units and provide theoretical support for highly efficient utilization of solar energy.

Heat absorption characteristics of gas in a solar fluidized bed receiver with carbon nanotubes

Carbon nanotubes (CNTs) have been proposed as new candidate particles to enhance the utilization efficiency of solar energy in solar fluidized bed receiver (SFBR) for solar air heating in low- and mid-temperature ranges. Heat absorption characteristics of the CNTs have been determined in a SFBR (50 mm i.d. X 150 mm high). Two types of experimental particles were used which consisted of multi-walled CNTs with different nanotube shapes, such as entangled CNTs (ENCNTs) and vertically aligned CNTs (VACNTs). The particle dynamics and heat absorption characteristics of CNTs were studied and compared with those of silicon carbide (SiC), a conventional particle. CNTs showed lower pressure fluctuation with relatively uniform particle behavior in the freeboard compared to SiC. The outlet gas temperatures of the receiver with CNTs were higher than those inside the fluidized bed above 0.10 m/s of gas velocity. The temperature increment of gas per irradiance (ΔT/IDNI) decreased with increasing gas velocity. VACNTs, which are characterized by the coexistence of aggregates and nanotubes in the freeboard, showed a higher value of ΔT/IDNI than ENCNTs for the same gas velocity. The relative heat absorption temperature (T*) decreased with increasing gas velocity, and dropped below 1.0 at the solid holdup of 0.04, indicating that the freeboard region’s contribution to the receiver’s heat absorption increased. VACNTs and ENCNTs showed maximum thermal efficiencies of 26.7 % and 30.5 % at gas velocities of 0.12 and 0.16 m/s, respectively, which was 33 % higher than that of SiC. Considering the particle properties and particle dynamics, the obtained thermal efficiencies in the present and previous studies were correlated with the Reynolds, Archimedes and Prandtl numbers and the ratios of the specific heat capacities of the particles to the gas.

Construction of polyoxometalate-based metal−organic frameworks through covalent bonds for enhanced visible light-driven coupling of alcohols with amines

Broad spectral response and rapid carrier transport are essential in making efficient photocatalysts. In this work, we utilized Keggin-type polyoxometalates (POMs) [CoIIW12O40]6– as metal-to-metal charge transfer (MMCT) chromophores and assembled them into metal–organic frameworks (MOFs) to construct visible-light-responsive, noble metal-free crystalline POM-based MOFs (POMOFs) (CoW-1 and CoW-2). The precise introduction of MMCT chromophores extending the light absorption of POMOFs to the visible region and improving the solar energy utilization efficiency, meanwhile, the Cu-O-W covalent bonds constructed in CoW-1 makes the framework structure more robust, reduces the interfacial contact resistance, facilitates the electron transfer, suppresses the recombination of the electron-hole pairs, improves the charge carriers separation efficiency, and boosts the quantum efficiency, thus achieving high catalytic activity in the coupling reaction of benzyl alcohol with aniline under visible light irradiation (>400 nm). In the presence of CoW-1, the reaction conversion yield was measured as 92.6 % with turnover frequency reaching 374.4 h−1, and the apparent quantum yield at 595 nm was calculated as 17.5 %, besides, CoW-1 also exhibited high catalytic stability and reusability. To the best of our knowledge, this is the first work describing the enhanced photocatalytic performance of POMOFs based on the synergistic effect of MMCT and covalent linkage.