The development of atmospheric pressure N2 reduction to NH3 is attracting much attention in green chemistry, yet it is still a challenge to obtain satisfactory activity under mild conditions. Herein, an efficient near-infrared (NIR) photothermal catalysis reduction of N2 constitutes an occurrence is reported. With or without V-substitute polyoxometalates (POMs) loaded on the surface of Fe-chelated polydopamine (Fe-PDA) photothermal support through the electrostatic interactions, NIR photothermal catalysts POMs@Fe-PDA are fabricated. The induction of “FeV” cofactor facilitates electron transfer between V(V)/V(IV)&Fe(III)/Fe(II) and N2, thereby activating N2 molecule. The synergy between the catalytic activity of V-POMs and the local NIR photothermal effect of Fe-PDA dramatically enhances N2 reduction. Noticeably, PMo10V2@Fe-PDA exhibits a significantly enhanced NH3 production rate of 181.1 μmol·L−1 with a turnover frequency of 1006.1 mmol·M−1·h−1 under 808 nm NIR laser radiation, being the highest values reported at atmospheric pressure. We expect that this work could provide an alternative approach for photothermal catalysis N2 reduction under mild conditions.
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The combination of donor–acceptor (D–A) structures presents a viable strategy for fabricating covalent organic frameworks (COFs) with exceptional photocatalytic performances. Nevertheless, the selection of functional groups on donor or acceptor building blocks and their effect on the macroscopic properties of COFs are ambiguous. In this study, we tactfully synthesized a pair of Py-DBT-COFs from the same pyrene (Py) donor and 4,7-diphenylbenzo[c][1,2,5]thiadiazole (DBT) acceptor cores with distinct primitive functional groups. The primitive functional groups of building units determine the photocatalytic properties of corresponding Py-DBT-COFs. Specifically, Py-C-DBT-COF synthesized from Py-4CHO and DBT-2NH2 showcases a splendid H2 evolution rate as high as 21,377.7 μmol/(g·h) (with 5 wt.% Pt) originating from better charge transfer capacity, which is significantly superior to that of Py-N-DBT-COF constructed from Py-4NH2 and DBT-2CHO. The distinct photocatalytic performances of the two COFs are demonstrated to originate from the different charge separation and transfer capabilities. This work supplies a new avenue for optimizing the photocatalytic performance of D–A COFs from the perspective of primitive functional group selections.
The continuous and sustainable photo-activity on micro- or nano-carriers has always been a key stepping stone in the industrialization of photo-catalysis, photo-synthesis, and photo-degradation. Herein, we report a new series of positively charged hollow microspheres carrying porphyrin moieties. Such hollow spheres are formed through crosslinking of well-ordered porous thin laminates, initiated by co-assembly of regular monomers and those decorated with porphyrin moieties. On the surface of an individual sphere, densely distributed positive sites attract anionic reactants. The superficial porphyrin decomposes the accumulated reactants under 1 Sun. After degradation and release of products, the photoactive sites are thereby renewed. We demonstrate that polymer network (1:10) exhibited superior sustainable photocatalytic performance with complete degradation of methyl orange (MO) in 40 min with no observable performance deterioration after six cycles. The established close loop of adsorption–reaction–release cycle makes possible many efficient and continuous photo-catalytic processes.
Chemodynamic therapy (CDT) offers a promising alternative to conventional cancer treatment. However, the limited acidity and H2O2 concentration in tumor microenvironment (TME) severely impair the anticancer effects of CDT. In this study, we report a microemulsion-assisted coassembly method to prepare iron(III) tetraphenylporphyrin (FeTPP) and magnetic (Fe3O4) nanocomposite material (FeTPP@Fe3O4), using photoactive FeTPP and Fe3O4 nanocrystals as building blocks. The self-assembling nature of FeTPP results in disordered aggregation and fluorescence quenching, leading to a high light-to-heat conversion efficiency. Continuously, the photo-thermal effect enhances the catalytic decomposition of hydrogen peroxide (H2O2) in the Fenton reaction on Fe3O4 nanocrystals to generate highly toxic hydroxyl radicals (·OH) to destroy cancer cells. This cascade reaction produces a synergistic therapeutic effect between CDT and photothermal therapy (PTT), which significantly amplifies the therapeutic effect and enhances the treatment outcome of cancer patients. The highly efficient tumor catalytic therapy in vivo results confirmed that this nanomedicine treatment is an excellent biocompatible catalytic nanomedicine therapy achieved through a photo-enhanced Fenton reaction activity approach.
Molecular self-assembly is a natured-inspired strategy to integrate individual functional molecules into supramolecular nanostructured materials through noncovalent bond interactions for solar to fuel conversion. However, the design and engineering of the morphology, size, and orderly stacking of supramolecular nanostructures remain a great challenge. In this study, regular porphyrin nanocrystals with different orderly stacked structures are synthesized through noncovalent self-assembly of Pt(II) meso-tetra (4-carboxyphenyl) porphine (PtTCPP), using surfactants with different electronegativity. The synergy of noncovalent bond interactions between porphyrin molecules, and between porphyrin molecules and surfactants resulted in different molecular packing patterns. Due to the spatial ordering of PtTCPP molecules, the different nanocrystals exhibit both collective optical properties and morphology-dependent activities in photocatalytic hydrogen production. The measurements of the photodeposition of dual cocatalysts showed that the photogenerated electrons and holes selectively aggregated at different active sites, revealing separation pathways and directional transfer of photogenerated electrons and holes in the assemblies. This study provides a new strategy to exert rational control over porphyrin self-assembly nanocrystals for highly efficient water splitting.
The use of functional nanoparticles as peroxidase-like (POD-like) catalyst has recently become a focus of research in cancer therapy. Phthalocyanine is a macrocyclic conjugated metal ligand, which is expected to achieve a high POD-like catalytic activity, generating free radicals and inhibiting the proliferation of cancer cells. In this paper, we synthesized phthalocyanine nanocrystals with different structures through noncovalent self-assembly confined within micro-emulsion droplets, and manganese phthalocyanine (MnPc) possessing a metal–N–C active center was used as the building block. These nano-assemblies exhibit shape-dependent POD-like catalytic activities, because the emulsifier and MnPc co-mixed assembly reduced the close packing between MnPc molecules and exposed more active sites. The assembly had a water-dispersed nanostructure, which is conducive to accumulation at tumor sites through the enhanced permeability and retention effect (EPR). Because of a highly efficient microenvironmental response, the assembly showed higher catalytic activity only emerged under the acidic tumor-like microenvironment, but caused less damage to normal tissues in biomedical applications. In vivo and in vitro catalytic therapy tests showed excellent anti-tumor effects. This work explored a new way for the application of metal–organic macromolecules such as MnPc as nanozymes for catalytic tumor therapy.
Nanoparticle photosensitizers possess technical advantages for photocatalytic reactions due to enhanced light harvesting and efficient charge transport. Here we report synthesis of semiconductor nanoparticles through covalent coupling and assembly of metalloporphyrin with condensed carbon nitride. The resultant nanoparticles consist of light harvesting component from the condensed carbon nitride and photocatalytic sites from the metalloporphyrins. This synergetic particle system effectively initiates efficient charge separation and transport and exhibits excellent photocatalytic activity for CO2 reduction. The CO production rate can reach up to 57 μmol/(g·h) with a selectivity of 79% over competing H2 evolution. Controlled experiments demonstrate that the combination of light harvesting with photocatalytic activity via covalent assembly is crucial for the high photocatalytic activity. Due to effective charge separation and transfer, the resultant nanoparticle photocatalysts show exceptional photo stability against photo-corrosion under light irradiation, enabling for long-term utilization. This research opens a new way for the development of stable, effective nanoparticle photocatalysts using naturally abundant porphyrin pigments.
In order to broaden the absorption range of graphitic carbon nitride, one of the common methods is to couple the well-known photosensitizer porphyrin with graphitic carbon nitride through van der Waals weak interactions. To date, to combine porphyrin with graphitic carbon nitride through covalent interactions has not been settled. In this work, through rational molecular design, we successfully incorporated porphyrin into the matrixes of graphitic carbon nitride by covalent bonding via one-pot thermal copolymerization. The resultant material not only can widen the absorption range but also possess the enlarged specific surface area and construction intramolecular heterojunctions which can contribute to improve electron-holes separation efficiency. The resultant photocatalyst exhibited enhanced H2 production rate (7.6 mmol·g-1·h-1) and with the apparent quantum efficiency (AQE) of 13.3% at 450 nm. At the same time, this method opens a way to fabricate graphitic carbon nitride nanosheets via bottom-up strategy.