Photocatalytic Chemical CO2 Fixation by Cu-BDC Nanosheet@Macroporous–Mesoporous-TiO2 under Mild Conditions

Interconnected Periodic Macroporous NaNbO3 for High-Efficiency Solar-Driven Photocatalytic Hydrogen Evolution

Highly ordered periodic macroporous structures have been extensively utilized to significantly enhance the photocatalytic activity. However, constructing 3D interconnected ordered porous ternary nanostructures with highly crystalline frameworks remains a formidable challenge. Here, we introduce the design and fabrication of 3D interconnected periodic macroporous NaNbO3 (PM NaNbO3) to effectively increase the density of surface-active sites and optimize the photogenerated carrier-transfer efficiency. By incorporating Pt as a cocatalyst, PM NaNbO3 exhibits an exceptional photocatalytic hydrogen generation rate of 10.04 mmol h-1 g-1, which is approximately six and five times higher than those of calcined NaNbO3 (C-NaNbO3) and hydrothermal NaNbO3 (H-NaNbO3), respectively. This outstanding performance can be attributed to the synergistic effects arising from its well-interconnected pore architecture, large surface area, enhanced light absorption capability, and improved charge carrier separation and transport efficiency. The findings presented in this study demonstrate an innovative approach toward designing hierarchically periodic macroporous materials for solar-driven hydrogen production.

Photoelectrocatalytic Utilization of CO2 : A Big Show of Si-based Photoelectrodes

CO2 is a greenhouse gas that contributes to environmental deterioration; however, it can also be utilized as an abundant C1 resource for the production of valuable chemicals. Solar-driven photoelectrocatalytic (PEC) CO2 utilization represents an advanced technology for the resourcing of CO2 . The key to achieving PEC CO2 utilization lies in high-performance semiconductor photoelectrodes. Si-based photoelectrodes have attracted increasing attention in the field of PEC CO2 utilization due to their suitable band gap (1.1 eV), high carrier mobility, low cost, and abundance on Earth. There are two pathways to PEC CO2 utilization using Si-based photoelectrodes: direct reduction of CO2 into small molecule fuels and chemicals, and fixation of CO2 with organic substrates to generate high-value chemicals. The efficiency and product selectivity of PEC CO2 utilization depends on the structures of the photoelectrodes as well as the composition, morphology, and size of the catalysts. In recent years, significant and influential progress has been made in utilizing Si-based photoelectrodes for PEC CO2 utilization. This review summarizes the latest research achievements in Si-based PEC CO2 utilization, with a particular emphasis on the mechanistic understanding of CO2 reduction and fixation, which will inspire future developments in this field.

Metal-Organic-Framework-Derived Bromine and Nitrogen Dual-Doped Porous Carbon for CO2 Photocycloaddition Reaction

The cycloaddition of CO2 with epoxides driven by light irradiation is an intriguing approach to preparing cyclic carbonates. However, it remains a great challenge to achieve high photocatalytic efficiency in the absence of a cocatalyst. Herein, we explored a metal-organic-framework (MOF)-templated pyrolysis strategy to prepare uniform bromine ions/nitrogen-codoped carbon materials (Br-CN) as low-cost photocatalysts for CO2 cycloaddition. The optimal catalyst Br-CN-1-550 can be used as a photocatalyst to catalyze CO2 cycloaddition, remarkably reducing the energy consumption. As a result of its benefits of high photothermal efficiency and rich nucleophilic sites (Br ions), BN-CN-1-550 affords a 9 times higher yield of 4-(chloromethyl)-1,3-dioxolan-2-one than that of the ZIF-8-derived CN under cocatalyst-free conditions and light irradiation (300 mW·cm-2 full-spectrum irradiation, 10 h). This strategy provides a cost-effective way to obtain cyclic carbonate under cocatalyst-free conditions.

CO2 Cycloaddition under Ambient Conditions over Cu-Fe Bimetallic Metal-Organic Frameworks

Carbon dioxide cycloaddition into fine chemicals is prospective technology to solve energy crisis and environmental issues. However, high temperature and pressure are usually required in the conventional cycloaddition reactions of CO2 with epoxides. Moreover, metal active sites play a vital role in the CO2 cycloaddition, but it is still unclear. Herein, we select the isostructural MOF-919-Cu-Fe and MOF-919-Cu-Al as models to promote the performance and clarify the effects of metal type on the CO2 cycloaddition. The MOF-919-Cu-Fe with exposed Fe and Cu Lewis acid sites reaches the CO2 cycloaddition with over 99.9% conversion and over 99.9% selectivity at room temperature and a 1 bar CO2 atmosphere, 3.0- and 52.6-fold higher than those of the MOF-919-Cu-Al with Al and Cu sites (33.8%) and the 1H-pyrazole-4-carboxylic acid, Fe, and Cu mixed system (1.9%), respectively. The proposed mechanism demonstrated that the exposed Fe3+ sites facilitate the ring opening of epoxide and CO2 activation to boost the CO2 cycloaddition reaction. This work provides a new insight to tune the catalytic sites of MOFs to achieve high performance for CO2 fixation.

Co-Doped Mn3 O4 Nanocubes via Galvanic Replacement Reactions for Photocatalytic Reduction of CO2 with High Turnover Number

The synthesis of Co-doped Mn₃ O₄ nanocubes was achieved via galvanic replacement reactions for photo-reduction of CO₂ . Co@Mn₃ O₄ nanocubes could efficiently photo-reduce CO₂ to CO with a remarkable turnover number of 581.8 using [Ru(bpy)₃ ]Cl₂  ⋅ 6H₂ O as photosensitizer and triethanolamine as sacrificial agent in acetonitrile and water. The galvanic replaced Co species are homogeneously distributed at the outer surface of Mn₃ O₄ , providing catalytic active sites during CO₂ reduction reactions, which facilitate the separation and migration of photogenerated charge carriers, further benefiting the outstanding photocatalytic performance of CO₂ reduction. Density functional theory calculations revealed that the decreasing of conduction band maximum in Co@Mn₃ O₄ was beneficial to the electron attachment from the excited sensitized molecule, which promoted photocatalytic reduction of CO₂ .

Recent Advances in Porous Materials for Photocatalytic CO2 Reduction

Photocatalytic CO₂ reduction into solar fuels is a promising technology for addressing energy and CO₂ emission issues. Because of the superior properties in CO₂ adsorption and activation, molecular diffusion, light absorption, and charge separation and transfer, porous materials have been developed into a multifunctional platform for photocatalytic CO₂ reduction. In this Perspective, we first discuss the emerging trends of CO₂ reduction in major inorganic porous materials-based photocatalysts, such as mesoporous materials, macroporous materials, hollow materials, hierarchically porous materials, and zeolites. Prospects and challenges in the development of porous materials-based photocatalysts are then outlined. Finally, we envision feasible solutions for the deployment of porous materials to enhance photocatalytic CO₂ reduction performance.

Hierarchically ordered macroporous TiO2 architecture via self-assembled strategy for environmental remediation

Hierarchical orderd macroporous TiO₂ architecture (HOMTA) was prepared with aid of ethylenediamine (EDA) and investigated the impact of amine molecules on the properties of TiO₂ architecture. The different variation of amine molecules (EDA) leads to tunning the morphology under hydrothermal approach which is confirmed by FESEM and TEM analysis. The XRD and Raman studies confirms the crystal structure of anatase and brookite phase of TiO₂. The surface of the architecture strongly depended on the concentration of EDA which plays a vital role in surface area which is revealed by Brunauer Emmett-Teller (BET) analysis. The obtained HOMTA was employed as photocatalyst and active photoanode in the dye sensitized solar cells (DSSC). The DSSC device exhibits excellent efficiency (η) of 5.27% for the EDA capped TiO₂ (S5) which had high surface area (167.11 m²/g) for better dye loading, whereas the lower concentration of EDA capped TiO₂ (S1, S2, S3 and S4) resulted the efficiency of 2.14, 3.90, 3.25 and 4.37%, respectively. The efficiency of photocatlysis degradation of the prepared samples (S1, S2, S3, S4 and S5) was 94.8, 90.47, 91.41, 91.32 and 93.75% under light source. The excellent photocatalysis property was achieved by S5 within 6 min due to high surface area which inducing more active site.

Nickel Nanoparticles Immobilized over Mesoporous SBA-15 for Efficient Carbonylative Coupling Reactions Utilizing CO2: A Spotlight

Ecofriendly routes for the synthesis of carbamates and carbonylative coupling products such as benzyl formate derivatives are very demanding for both academia and industries. Foreseeing a sustainable green future, we systematically analyzed the synthesis history of both these chemicals, mentioning their pros and cons. As a step towards green chemistry, here we have optimized the reaction conditions for the synthesis of various benzyl formates from corresponding benzyl halides and carbamates from substituted anilines and alkyl halides catalyzed by Ni(0) nanoparticles (NPs) immobilized over amine-functionalized ordered mesoporous SBA-15 material in the presence of CO₂ as C1 source. This spotlight on applications is aimed to provide a clear outlook to date regarding the gradual progress in the synthesis of both these aforementioned chemicals and finally addresses further efforts for overcoming the current challenges.

Catalytic amplification based on hierarchical heterogeneity bimetal-organic nanostructures with peroxidase-like activity

In this paper, integrating heterometallic units and nanostructures into metal-organic frameworks (MOFs) were applied to improve the sensitivity of detecting hydrogen peroxide (H₂O₂) in neutral solution. The bimetal-MOFs (CuCo-BDC) and GO composite (CuCo-BDC/GO) were first synthesized via an ordinary one-step solvothermal synthesis. The CuCo-BDC/GO with admirable peroxidase-like catalytic activity could be applied to detect H₂O₂. The results have low detection limit of 69 nM (S/N = 3) and a wide linear detection range, from 100 nM to 3.5 mM. This is superior to recently published biosensors based on noble metal nanomaterials, which confirms CuCo-BDC/GO as the MOF electrocatalysts with high performance. The remarkable electroanalytical performance of CuCo-BDC/GO is due to the presence of numerous open metal active sites, the synergistic effect of Cu²⁺ and Co²⁺, hierarchical structure with high-specific surface areas and the marvelous electrochemical properties of GO. Therefore, CuCo-BDC/GO is a powerful candidate for detecting H₂O₂ in electrochemical biosensing fields. Moreover, H₂O₂ detection in real samples can be done with the CuCo-BDC/GO, including human serum samples. Therefore, the novel CuCo-BDC/GO is a promising catalyst that can be applied in biotechnological and environmental applications.

Low-temperature processed tantalum/niobium co-doped TiO2electron transport layer for high-performance planar perovskite solar cells

A low-temperature preparation process is significantly important for scalable and flexible devices. However, the serious interface defects between the normally used titanium dioxide (TiO₂) electron transport layer (ETL) obtained via a low-temperature method and perovskite suppress the further improvement of perovskite solar cells (PSCs). Here, we develop a facile low-temperature chemical bath method to prepare a TiO₂ETL with tantalum (Ta) and niobium (Nb) co-doping. Systematic investigations indicate that Ta/Nb co-doping could increase the conduction band level of TiO₂and could decrease the trap-state density, boosting electron injection efficiency and reducing the charge recombination between the perovskite/ETL interface. A superior power conversion efficiency of 19.44% can be achieved by a planar PSC with a Ta/Nb co-doped TiO₂ETL, which is much higher than that of pristine TiO₂(17.60%). Our achievements in this work provide new insights on low-temperature fabrication of low-cost and highly efficient PSCs.

Interface Engineering of Co-LDH@MOF Heterojunction in Highly Stable and Efficient Oxygen Evolution Reaction

The electrochemical splitting of water into hydrogen and oxygen is considered one of the most promising approaches to generate clean and sustainable energy. However, the low efficiency of the oxygen evolution reaction (OER) acts as a bottleneck in the water splitting process. Herein, interface engineering heterojunctions between ZIF-67 and layered double hydroxide (LDH) are designed to enhance the catalytic activity of the OER and the stability of Co-LDH. The interface is built by the oxygen (O) of Co-LDH and nitrogen (N) of the 2-methylimidazole ligand in ZIF-67, which modulates the local electronic structure of the catalytic active site. Density functional theory calculations demonstrate that the interfacial interaction can enhance the strength of the Co-Oout bond in Co-LDH, which makes it easier to break the H-Oout bond and results in a lower free energy change in the potential-determining step at the heterointerface in the OER process. Therefore, the Co-LDH@ZIF-67 exhibits superior OER activity with a low overpotential of 187 mV at a current density of 10 mA cm-2 and long-term electrochemical stability for more than 50 h. This finding provides a design direction for improving the catalytic activity of OER.

Encapsulation of Porphyrin-Fe/Cu Complexes into Coordination Space for Enhanced Selective Oxidative Dehydrogenation of Aromatic Hydrazides

The encapsulation of specific nanoentities into hollow nanomaterials derived from metal organic frameworks has attracted continuous and growing research attentions owing to their unique structural properties and unusual synergistic functions. Herein, using the phase transformation of uniform rhombi dodecahedron ZIF-67, hollow nano-shell with a well-defined morphology is successfully prepared. Particularly, the iron-oxygen complex, that is formed by the interaction between TCPP-Fe/Cu (TCPP = tetrakis(4-carboxyphenyl)-porphyrin) and oxygen, can be acted as an ideal proton acceptor for practical organic reactions. Considering the unique adaptability of hollow ZIFs (named HZ) to the transformation of encapsulated TCPP-Fe/Cu bimetallic catalytic active sites, a heterogeneous catalyst (defined as HZ@TCPP-Fe/Cu) through morphology-controlled thermal transformation and rear assemble processes is designed and constructed. Under heterogeneous conditions, HZ@TCPP-Fe/Cu serves as a multifunctional molecular selector to promote the oxidative dehydrogenation of different aromatic hydrazide derivatives with high selectivity toward primary carbon among primary, secondary, and tertiary carbons that are unachievable by other traditional homogeneous catalysts. The high catalytic activity, selectivity, and recyclability of the catalyst proposed here are attractive advantages for an alternative route to the environmentally benign transformation of aromatic hydrazides to aromatic azobenzene.