Opportunities and challenges for plastic depolymerization by biomimetic catalysis.

Plastic waste has imposed significant burdens on the environment. Chemical recycling allows for repeated regeneration of plastics without deterioration in quality, but often requires harsh reaction conditions, thus being environmentally unfriendly. Enzymatic catalysis offers a promising solution for recycling under mild conditions, but it faces inherent limitations such as poor stability, high cost, and narrow substrate applicability. Biomimetic catalysis may provide a new avenue by combining high enzyme-like activity with the stability of inorganic materials. Biomimetic catalysis has demonstrated great potential in biomass conversion and has recently shown promising progress in plastic degradation. This perspective discusses biomimetic catalysis for plastic degradation from two perspectives: the imitation of the active centers and the imitation of the substrate-binding clefts. Given the chemical similarity between biomass and plastics, relevant work is also included in the discussion to draw inspiration. We conclude this perspective by highlighting the challenges and opportunities in achieving sustainable plastic recycling via a biomimetic approach.

Ammonia Electrosynthesis from Nitrate Using a Ruthenium-Copper Cocatalyst System: A Full Concentration Range Study.

Electrochemical synthesis of ammonia via the nitrate reduction reaction (NO3RR) has been intensively researched as an alternative to the traditional Haber-Bosch process. Most research focuses on the low concentration range representative of the nitrate level in wastewater, leaving the high concentration range, which exists in nuclear and fertilizer wastes, unexplored. The use of a concentrated electrolyte (≥1 M) for higher rate production is hampered by poor hydrogen transfer kinetics. Herein, we demonstrate that a cocatalytic system of Ru/Cu2O catalyst enables NO3RR at 10.0 A in 1 M nitrate electrolyte in a 16 cm2 flow electrolyzer, with 100% faradaic efficiency toward ammonia. Detailed mechanistic studies by deuterium labeling and operando Fourier transform infrared (FTIR) spectroscopy allow us to probe the hydrogen transfer rate and intermediate species on Ru/Cu2O. Ab initio molecular dynamics (AIMD) simulations reveal that adsorbed hydroxide on Ru nanoparticles increases the density of the hydrogen-bonded water network near the Cu2O surface, which promotes the hydrogen transfer rate. Our work highlights the importance of engineering synergistic interactions in cocatalysts for addressing the kinetic bottleneck in electrosynthesis.

Diatomic iron nanozyme with lipoxidase-like activity for efficient inactivation of enveloped virus.

Enveloped viruses encased within a lipid bilayer membrane are highly contagious and can cause many infectious diseases like influenza and COVID-19, thus calling for effective prevention and inactivation strategies. Here, we develop a diatomic iron nanozyme with lipoxidase-like (LOX-like) activity for the inactivation of enveloped virus. The diatomic iron sites can destruct the viral envelope via lipid peroxidation, thus displaying non-specific virucidal property. In contrast, natural LOX exhibits low antiviral performance, manifesting the advantage of nanozyme over the natural enzyme. Theoretical studies suggest that the Fe-O-Fe motif can match well the energy levels of Fe2 minority ß-spin d orbitals and pentadiene moiety π* orbitals, and thus significantly lower the activation barrier of cis,cis-1,4-pentadiene moiety in the vesicle membrane. We showcase that the diatomic iron nanozyme can be incorporated into air purifier to disinfect airborne flu virus. The present strategy promises a future application in comprehensive biosecurity control.

Addressing the quantitative conversion bottleneck in single-atom catalysis.

Single-atom catalysts (SACs) offer many advantages, such as atom economy and high chemoselectivity; however, their practical application in liquid-phase heterogeneous catalysis is hampered by the productivity bottleneck as well as catalyst leaching. Flow chemistry is a well-established method to increase the conversion rate of catalytic processes, however, SAC-catalysed flow chemistry in packed-bed type flow reactor is disadvantaged by low turnover number and poor stability. In this study, we demonstrate the use of fuel cell-type flow stacks enabled exceptionally high quantitative conversion in single atom-catalyzed reactions, as exemplified by the use of Pt SAC-on-MoS2/graphite felt catalysts incorporated in flow cell. A turnover frequency of approximately 8000 h-1 that corresponds to an aniline productivity of 5.8 g h-1 is achieved with a bench-top flow module (nominal reservoir volume of 1 cm3), with a Pt1-MoS2 catalyst loading of 1.5 g (3.2 mg of Pt). X-ray absorption fine structure spectroscopy combined with density functional theory calculations provide insights into stability and reactivity of single atom Pt supported in a pyramidal fashion on MoS2. Our study highlights the quantitative conversion bottleneck in SAC-mediated fine chemicals production can be overcome using flow chemistry.

Conductive, Large-Area, and Continuous 7,7,8,8-Tetracyanoquinodimethane@HKUST-1 Thin Films Fabricated Using Solution Shearing.

Most metal-organic frameworks (MOFs) have an insulating nature due to their porosity and redox-inactive organic components. The electrical conductivity of the prototypical MOF, HKUST-1, can be tuned by infiltrating a small-molecule organic semiconductor, 7,7,8,8-tetracyanoquinodimethane (TCNQ), into the HKUST-1 pores, creating TCNQ@HKUST-1. However, current processes of creating TCNQ@HKUST-1 films have many roadblocks such as slow crystallization rates, which limit high throughput production, and the formation of Cu(TCNQ) as a byproduct, which affects the electrical conductivity and degrades the chemical structure of HKUST-1. In this work, we show that HKUST-1 films can be rapidly synthesized over large areas with consistent thickness and no pinholes via a meniscus-guided coating technique called solution shearing. The subsequent pore activation process and TCNQ impregnation can be completed via solvent exchange to minimize the formation of the Cu(TCNQ) byproduct, and we obtain an increase in electrical conductivity of the solution-sheared TCNQ@HKUST-1 thin films of over 7 orders of magnitude, reaching a maximum value of 2.42 × 10-2 S m-1 when TCNQ is incorporated for 10 days. The conductivity of solution-sheared TCNQ@HKUST-1 is higher compared to films formed by high-pressure pelletization of TCNQ@HKUST-1. We show that solution shearing can produce large-area thin films rapidly and reduce the formation of grain boundaries better than pelletization, allowing for large-area electronics with both charge transport and porosity for applications as sensors and electronics.

Fabrication of copper phthalocyanine/reduced graphene oxide nanocomposites for efficient photocatalytic reduction of hexavalent chromium.

Copper(II) phthalocyanine (CuPc) and non-peripheral octamethyl-substituted copper(II) phthalocyanine (N-CuMe2Pc) were combined with reduced graphene oxide (rGO) via a precipitation method to form CuPc/rGO and N-CuMe2Pc/rGO nanocomposites, respectively. CuPc nanorods are distributed on rGO, and N-CuMe2Pc exists as nanorods and nanoparticles on rGO. The Cr(VI) removal ratio of N-CuMe2Pc/rGO exposed in simulated sunlight is 99.0% with a fast photocatalytic reaction rate of 0.0320 min-1, which is approximately 1.5 times faster than that of CuPc/rGO (0.0215 min-1) and far surpasses that of pristine phthalocyanine and rGO. As an electron acceptor, rGO can suppress the recombination of photo-induced electron-hole pairs and also can provide a large surface area for Cr(VI) removal, both of which are beneficial to the reducing capacity of the nanocomposites. The higher removal efficiency of N-CuMe2Pc/rGO compared with that of CuPc/rGO is attributed to the higher specific surface area, higher light harvesting, higher conductivity and more negative lowest unoccupied molecular orbital level of N-CuMe2Pc/rGO. The N-CuMe2Pc/rGO nanocomposite shows excellent photochemical recyclability which is essential for application in wastewater treatment.

Dual Defect-Passivation Using Phthalocyanine for Enhanced Efficiency and Stability of Perovskite Solar Cells.

Semiconducting molecules have been employed to passivate traps extant in the perovskite film for enhancement of perovskite solar cells (PSCs) efficiency and stability. A molecular design strategy to passivate the defects both on the surface and interior of the CH3 NH3 PbI3 perovskite layer, using two phthalocyanine (Pc) molecules (NP-SC6 -ZnPc and NP-SC6 -TiOPc) is demonstrated. The presence of lone electron pairs on S, N, and O atoms of the Pc molecular structures provides the opportunity for Lewis acid-base interactions with under-coordinated Pb2+ sites, leading to efficient defect passivation of the perovskite layer. The tendency of both NP-SC6 -ZnPc and NP-SC6 -TiOPc to relax on the PbI2 terminated surface of the perovskite layer is also studied using density functional theory (DFT) calculations. The morphology of the perovskite layer is improved due to employing the Pc passivation strategy, resulting in high-quality thin films with a dense and compact structure and lower surface roughness. Using NP-SC6 -ZnPc and NP-SC6 -TiOPc as passivating agents, it is observed considerably enhanced power conversion efficiencies (PCEs), from 17.67% for the PSCs based on the pristine perovskite film to 19.39% for NP-SC6 -TiOPc passivated devices. Moreover, PSCs fabricated based on the Pc passivation method present a remarkable stability under conditions of high moisture and temperature levels.

In situ synthesis of N-CoMe2Pc/rGO nanocomposite with enhanced photocatalytic activity and stability in Cr(VI) reduction.

Graphene-based composites are widely used in the photocatalytic treatment of heavy-metal ions or dyes. In this study, we developed a facile in situ precipitation method for preparing a non-peripheral octamethyl-substituted cobalt(II)phthalocyanine (N-CoMe2Pc)/reduced graphene oxide (rGO) nanocomposite as an efficient photocatalyst. The physical and chemical properties of the nanocomposite were investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and ultraviolet-visible, ultraviolet photoelectron, Fourier-transform infrared, Raman, and x-ray photoelectron spectroscopies. The results showed that the N-CoMe2Pc nanoparticles were immobilized on rGO nanosheets via π-π stacking interactions. The photocatalytic activity of the nanocomposite in the reduction of hexavalent chromium [Cr(VI), 10 mg/l] under visible-light irradiation was investigated. The Cr(VI) removal ratio reached 99.5% with a high photocatalytic rate of 0.0359 min-1, which is ten times faster than that achieved with pristine N-CoMe2Pc. The high removal efficiency is attributed to the following: (1) the number of active sites provided by nanodot-like N-CoMe2Pc is larger than that provided by bulk Pc, which can increase the production of photogenerated carriers, and (2) enhanced charge carrier separation resulting from intimate contact between N-CoMe2Pc nanodots and GO nanosheets. The N-CoMe2Pc/rGO also showed excellent stability and reusability. The Cr(VI) removal efficiency was 93.2% after eight photocatalytic test cycles.

Molecular Design Strategy in Developing Titanyl Phthalocyanines as Dopant-Free Hole-Transporting Materials for Perovskite Solar Cells: Peripheral or Nonperipheral Substituents?

We demonstrate a molecular design strategy to enhance the efficiency of phthalocyanine (Pc)-based hole-transporting materials (HTMs) in perovskite solar cells (PSCs). Herein, two titanyl phthalocyanine (TiOPc) derivatives are designed and applied as dopant-free HTMs in planar n-i-p-structured PSCs. The newly developed TiOPc compounds possess eight n-hexylthio groups attached to either peripheral (P-SC6-TiOPc) or nonperipheral (NP-SC6-TiOPc) positions of the Pc ring. Utilizing these dopant-free HTMs in PSCs with a mixed cation perovskite as the light-absorbing material and tin oxide (SnO2) as the electron-transporting material (ETM) results in a considerably enhanced efficiency for NP-SC6-TiOPc-based devices compared to PSCs using P-SC6-TiOPc. Hence, all of the photovoltaic parameters, including power conversion efficiency (PCE), fill factor, open-circuit voltage, and short-circuit current density, are remarkably improved from 5.33 ± 1.01%, 33.34 ± 3.45%, 0.92 ± 0.18 V, and 17.33 ± 2.08 mA cm-2 to 15.83 ± 0.44%, 69.03 ± 1.59%, 1.05 ± 0.01 V, and 21.80 ± 0.36 mA cm-2, respectively, when using the nonperipheral-substituted TiOPc derivative as the HTM in a PSC. Experimental and computational analysis suggests more compact molecular packing for NP-SC6-TiOPc than P-SC6-TiOPc in the solid state due to stronger π-π interactions, leading to thin films with better quality and higher performance in hole extraction and transportation. PSCs with NP-SC6-TiOPc also offer much higher long-term stability than P-SC6-TiOPc-based devices under ambient conditions with a relative humidity of 75%.