2D Porphyrinic Metal-Organic Framework Nanosheets as Multidimensional Photocatalysts for Functional Materials

Enzyme-Mimic Photoinitiated Flow-Polymerization with High Stereoselectivity under Mild Conditions

Enzymatic reactions can achieve efficient flow-polymerization with specificity and high stereoselectivity. However, current enzyme-mimic polymerization systems cannot achieve high stereoregularity in flow reactions under mild conditions. This inefficient chain control may be due to the absence of a specific catalyst structure for the target monomer. This study reports a model of enzyme-mimic catalytic material for the polymerization of a specific monomer. In particular, the specific enzyme-mimic photoinitiated flow-polymerization of benzyl acrylate was realized at 22 °C using zinc porphyrin metal-organic framework (Zn-PMOF) membranes with one-dimensional nanochannels, achieving the efficient synthesis of highly heterotactic polymers. Under visible light irradiation, the zinc porphyrin core on the membrane surface could initiate polymerization, while copper porphyrin MOF with similar structures could not. The specific channel structure of the Zn-PMOF membrane provided space for stereochemical control. Control experiments, density functional theory simulations, and spectroscopic characterizations show that the combination of size effect and channel-monomer interactions realized higher monomer conversion and polymer stereoregularity in the flow reaction. Furthermore, the crystallinity, shear stress, and ionic conductivity of enzyme-mimic polymers were considerably better than those of bulk polymerization products. Thus, this study provides a method for enzyme-mimic polymerization with high stereoselectivity under mild conditions.

Better Together: Photoredox/Copper Dual Catalysis in Atom Transfer Radical Polymerization

Photomediated Atom Transfer Radical Polymerization (photoATRP) is an activator regeneration method, which allows for the controlled synthesis of well-defined polymers via light irradiation. Traditional photoATRP is often limited by the need for high-energy ultraviolet or violet light. These could negatively affect the control and selectivity of the polymerization, promote side reactions, and may not be applicable to biologically relevant systems. This drawback can be circumvented by an introduction of the catalytic amount of photocatalysts, which absorb visible and/or NIR light and, therefore, controlled, regenerative ATRP can be performed with the dual-catalytic cycle. Herein, a critical summary of recent developments in the field of dual-catalysis concerning Cu-catalyzed ATRP is provided. Contributions of involved species are examined mechanistically, followed by challenges and future directions towards the next generation of advanced functional macromolecular materials.

Porphyrin-Based Metal-Organic Framework Photocatalysts: Structure, Mechanism and Applications

In recent years, porphyrins have been frequently reported as photocatalysts due to their fascinating photochemical properties. However, porphyrins have the same shortcomings as other homogeneous photocatalysts, such as poor stability and difficulty in recovering. To solve this problem, it is a good strategy to form a porphyrin-based metal-organic framework (PMOF) by modifying porphyrin functional groups and adding metals as nodes to connect and control the arrangement of porphyrins. The metal nodes control the rigidity and connectivity of the porphyrin modules to order them in the MOF, which improves the stability of the porphyrins, avoids porphyrin aggregation and folding, and increases the active sites for photocatalytic reactions. This review summarized the research progress of PMOF photocatalysts in the last ten years and analyzed the effects of the spatial structure, porphyrin ligands, porphyrin central metals, and metal nodes of PMOF on the photocatalytic performance. The applications of PMOF-based photocatalysts in H2 production, CO2 reduction, pollutant degradation, and sterilization are reviewed. In addition, the mechanism of these processes is described in detail. Finally, some suggestions on the development of PMOF photocatalysts are put forward.

A novel Bi12O17Cl2/GO/Co3O4 Z-type heterojunction photocatalyst with ZIF-67 derivative modified for highly efficient degradation of antibiotics under visible light

Levofloxacin (LVX) is difficult to be naturally degraded by microorganisms in water, and its residues in water will pose significant risks to human health and ecological environment. In this study, Bi12O17Cl2 was used as the main body, Bi12O17Cl2/GO/Co3O4 composite photocatalyst was prepared by pyrolysis of zeolitic imidazolate framework-67 (ZIF-67) combined with in-situ precipitation method and used to degrade LVX. A sequence of characterizations shows that addition of Co3O4 and graphene oxide (GO) increases the visible light response range, improves the separation efficiency of photogenerated electrons and holes (e--h+) of photocatalyst, and thus improves the degradation efficiency of LVX. Under the optimal reaction conditions, the LVX degradation rate of Bi12O17Cl2/1.5GO/7.5Co3O4 can reach 91.2 % at 120 min, and its reaction rate constant is the largest (0.0151 min-1), which is 2.17, 13.14 and 1.53 times that of Bi12O17Cl2, Co3O4 and Bi12O17Cl2/7.5Co3O4, respectively, showing better photocatalytic performance. Simultaneously, the recycling stability of Bi12O17Cl2/1.5GO/7.5Co3O4 was also verified. The capture experiments and electron EPR test results showed that superoxide radicals (•O2-) and photogenerated holes (h+) were the primary active substances in the reaction process. Finally, combined with HPLC-MS results, the photocatalytic degradation pathway of LVX was derived. This work will provide a theoretical basis for the design of Metal Organic Frameworks (MOFs)-derivative modified Bi12O17Cl2-based photocatalysts.

Nanozyme Decorated Metal-Organic Framework Nanosheet for Enhanced Photodynamic Therapy Against Hypoxic Tumor

INTRODUCTION

Photodynamic therapy (PDT) has attracted increasing attention in the clinical treatment of epidermal and luminal tumors. However, the PDT efficacy in practice is severely impeded by tumor hypoxia and the adverse factors associated with hydrophobic photosensitizers (PSs), including low delivery capacity, poor photoactivity and limited ROS diffusion. In this study, Pt nanozymes decorated two-dimensional (2D) porphyrin metal-organic framework (MOF) nanosheets (PMOF@HA) were fabricated and investigated to conquer the obstacles of PDT against hypoxic tumors.

MATERIALS AND METHODS

PMOF@HA was synthesized by the coordination of transition metal iron (Zr4+) and PS (TCPP), in situ generation of Pt nanozyme and surface modification with hyaluronic acid (HA). The abilities of hypoxic relief and ROS generation were evaluated by detecting the changes of O2 and 1O2 concentration. The cellular uptake was investigated using flow cytometry and confocal laser scanning microscopy. The SMMC-7721 cells and the subcutaneous tumor-bearing mice were used to demonstrate the PDT efficacy of PMOF@HA in vitro and in vivo, respectively.

RESULTS

Benefiting from the 2D structure and inherent properties of MOF materials, the prepared PMOF@HA could not only serve as nano-PS with high PS loading but also ensure the rational distance between PS molecules to avoid aggregation-induced quenching, enhance the photosensitive activity and promote the rapid diffusion of generated radical oxide species (ROS). Meanwhile, Pt nanozymes with catalase-like activity effectively catalyzed intratumoral overproduced H2O2 into O2 to alleviate tumor hypoxia. Additionally, PMOF@HA, with the help of externally coated HA, significantly improved the stability and increased the cell uptake by CD44 overexpressed tumor cells to strengthen O2 self-supply and PDT efficacy.

CONCLUSION

This study provided a new strategy of integrating 2D porphyrin MOF nanosheets with nanozymes to conquer the obstacles of PDT against hypoxic tumors.

Exciton Dissociation into Charge Carriers in Porphyrinic Metal-Organic Frameworks for Light-Assisted Li-O2 Batteries

Light-assisted Li-O2 batteries exhibit a high round-trip efficiency attributable to the assistance of light-generated electrons and holes in oxygen reduction and evolution reactions. Nonetheless, the excitonic effect arising from Coulomb interaction between electrons and holes impedes carrier separation, thus hindering efficient utilization of photo-energy. Herein, porphyrinic metal-organic frameworks with (Fe2Ni)O(COO)6 clusters are used as photocathodes to accelerate exciton dissociation into charge carriers for light-assisted Li-O2 batteries. The coupling of Ni 3d and Fe 3d orbitals boosts ligand-to-metal cluster charge transfer, and hence drives exciton dissociation and activates O2 for superoxide (•O2 -) radicals, rather than singlet oxygen (1O2) under photoexcitation. These enable the light-assisted Li-O2 batteries with a low total overvoltage of 0.28 V and round-trip efficiency of 92% under light irradiation of 100 mW cm-2. This work highlights the excitonic effect in photoelectrochemical processes and provides insights into photocathode design for light-assisted Li-O2 batteries.

Sub-Nanometer Mono-Layered Metal-Organic Frameworks Nanosheets for Simulated Flue Gas Photoreduction

The dilemma between the thickness and accessible active site triggers the design of porous crystalline materials with mono-layered structure for advanced photo-catalysis applications. Here, a kind of sub-nanometer mono-layered nanosheets (Co-MOF MNSs) through the exfoliation of specifically designed Co3 cluster-based metal-organic frameworks (MOFs) is reported. The sub-nanometer thickness and inherent light-sensitivity endow Co-MOF MNSs with fully exposed Janus Co3 sites that can selectively photo-reduce CO2 into formic acid under simulated flue gas. Notably, the production efficiency of formic acid by Co-MOF MNSs (0.85 mmol g-1 h-1) is ≈13 times higher than that of the bulk counterpart (0.065 mmol g-1 h-1) under a simulated flue gas atmosphere, which is the highest in reported works up to date. Theoretical calculations prove that the exposed Janus Co3 sites with simultaneously available sites possess higher activity when compared with single Co site, validating the importance of mono-layered nanosheet morphology. These results may facilitate the development of functional nanosheet materials for CO2 photo-reduction in potential flue gas treatment.

Catalysis with Two-Dimensional Metal-Organic Frameworks: Synthesis, Characterization, and Modulation

The demand for the exploration of highly active and durable electro/photocatalysts for renewable energy conversion has experienced a significant surge in recent years. Metal-organic frameworks (MOFs), by virtue of their high porosity, large surface area, and modifiable metal centers and ligands, have gained tremendous attention and demonstrated promising prospects in electro/photocatalytic energy conversion. However, the small pore sizes and limited active sites of 3D bulk MOFs hinder their wide applications. Developing 2D MOFs with tailored thickness and large aspect ratio has emerged as an effective approach to meet these challenges, offering a high density of exposed active sites, better mechanical stability, better assembly flexibility, and shorter charge and photoexcited state transfer distances compared to 3D bulk MOFs. In this review, synthesis methods for the most up-to-date 2D MOFs are first overviewed, highlighting their respective advantages and disadvantages. Subsequently, a systematic analysis is conducted on the identification and electronic structure modulation of catalytic active sites in 2D MOFs and their applications in renewable energy conversion, including electrocatalysis and photocatalysis (electro/photocatalysis). Lastly, the current challenges and future development of 2D MOFs toward highly efficient and practical electro/photocatalysis are proposed.

Nucleic Acid-Binding Dyes as Versatile Photocatalysts for Atom-Transfer Radical Polymerization

Nucleic acid-binding dyes (NuABDs) are fluorogenic probes that light up after binding to nucleic acids. Taking advantage of their fluorogenicity, NuABDs have been widely utilized in the fields of nanotechnology and biotechnology for diagnostic and analytical applications. We demonstrate the potential of NuABDs together with an appropriate nucleic acid scaffold as an intriguing photocatalyst for precisely controlled atom-transfer radical polymerization (ATRP). Additionally, we systematically investigated the thermodynamic and electrochemical properties of the dyes, providing insights into the mechanism that drives the photopolymerization. The versatility of the NuABD-based platform was also demonstrated through successful polymerizations using several NuABDs in conjunction with diverse nucleic acid scaffolds, such as G-quadruplex DNA or DNA nanoflowers. This study not only extends the horizons of controlled photopolymerization but also broadens opportunities for nucleic acid-based materials and technologies, including nucleic acid-polymer biohybrids and stimuli-responsive ATRP platforms.

Rare-Earth Metal-Organic Framework with Nonplanar Porphyrin Groups for High-Efficiency Photocatalysis

Nonplanar porphyrins play crucial roles in many biological processes and chemical reactions as catalysts. However, the preparation of artificial nonplanar porphyrins suffers from complicated organic syntheses. Herein, we present a new rare-earth porphyrinic metal-organic framework (RE-PMOF), BUT-233, which is a three-dimensional (3D) framework structure with the flu topology consisting of 4-connected BBCPPP-Ph ligands H4BBCPPP-Ph = 5',5⁗-(10,20-diphenylporphyrin-5,15-diyl)bis([1,1':3',1″-terphenyl]-4,4'' dicarboxylic acid) and 8-connected Eu6 clusters. Noteworthily, the porphyrin cores of the BBCPPP-Ph ligands in BUT-233 are nonplanar with a ruffle-like conformation. In contrast, the porphyrin core in the free ligand H4BBCPPP-Ph is in a nearly ideally planar conformation, as confirmed by its single-crystal structure. BUT-233 is microporous with 6-8 Å pores and a Brunauer-Emmett-Teller (BET) surface area of 649 m2/g, as well as high stability in common solvents. The MOF was used as a photocatalyst for the oxidation degradation of a chemical warfare agent model molecule CEES (CEES = 2-chloroethyl ethyl sulfide) under the light-emitting diode (LED) irradiation and an O2 atmosphere at room temperature. CEES was almost completely converted into its nontoxic light-oxidized product CEESO (CEESO = 2-chloroethyl ethyl sulfoxide) in only 5 min with t1/2 = 2 min (t1/2: half-life). Moreover, the toxic deep-oxidized product 2-chloroethyl ethyl sulfone (CEESO2) was not detected. The catalytic activity of BUT-233 was high in comparison with those of some previously reported MOF catalysts. The results of photo/electrochemical property studies suggested that the high catalytic activity of BUT-233 was benefited from the presence of nonplanar porphyrin rings on its pore surface.

Challenges and Opportunities in Preserving Key Structural Features of 3D-Printed Metal/Covalent Organic Framework

Metal-organic framework (MOF) and covalent organic framework (COF) are a huge group of advanced porous materials exhibiting attractive and tunable microstructural features, such as large surface area, tunable pore size, and functional surfaces, which have significant values in various application areas. The emerging 3D printing technology further provides MOF and COFs (M/COFs) with higher designability of their macrostructure and demonstrates large achievements in their performance by shaping them into advanced 3D monoliths. However, the currently available 3D printing M/COFs strategy faces a major challenge of severe destruction of M/COFs' microstructural features, both during and after 3D printing. It is envisioned that preserving the microstructure of M/COFs in the 3D-printed monolith will bring a great improvement to the related applications. In this overview, the 3D-printed M/COFs are categorized into M/COF-mixed monoliths and M/COF-covered monoliths. Their differences in the properties, applications, and current research states are discussed. The up-to-date advancements in paste/scaffold composition and printing/covering methods to preserve the superior M/COF microstructure during 3D printing are further discussed for the two types of 3D-printed M/COF. Throughout the analysis of the current states of 3D-printed M/COFs, the expected future research direction to achieve a highly preserved microstructure in the 3D monolith is proposed.

Unleashing the Power of PET-RAFT Polymerization: Journey from Porphyrin-Based Photocatalysts to Combinatorial Technologies and Advanced Bioapplications

The emergence of photoinduced energy/electron transfer-reversible addition-fragmentation chain transfer polymerization (PET-RAFT) not only revolutionized the field of photopolymerization but also accelerated the development of porphyrin-based photocatalysts and their analogues. The continual expansion of the monomer family compatible with PET-RAFT polymerization enhances the range of light radiation that can be harnessed, providing increased flexibility in polymerization processes. Furthermore, the versatility of PET-RAFT polymerization extends beyond its inherent capabilities, enabling its integration with various technologies in diverse fields. This integration holds considerable promise for the advancement of biomaterials with satisfactory bioapplications. As researchers delve deeper into the possibilities afforded by PET-RAFT polymerization, the collaborative efforts of individuals from diverse disciplines will prove invaluable in unleashing its full potential. This Review presents a concise introduction to the fundamental principles of PET-RAFT, outlines the progress in photocatalyst development, highlights its primary applications, and offers insights for future advancements in this technique, paving the way for exciting innovations and applications.

Hot-Pressing Metal Covalent Organic Frameworks as Personal Protection Films

Effective personal protection is crucial for controlling infectious disease spread. However, commonly used personal protective materials such as disposable masks lack antibacterial/antiviral function and may lead to cross infection. Herein, a polyethylene glycol-assisted solvent-free strategy is proposed to rapidly synthesize a series of the donor-acceptor metal-covalent organic frameworks (MCOFs) (i.e., GZHMU-2, JNM-1, and JNM-2) under air atmosphere and henceforth extend it via in situ hot-pressing process to prepare MCOFs based films with photocatalytic disinfect ability. Best of them, the newly designed GZHMU-2 has a wide absorption spectrum (200 to 1500 nm) and can efficiently produce reactive oxygen species under sunlight irradiation, achieving excellent photocatalytic disinfection performance. After in situ hot-pressing as a film material, the obtained GZHMU-2/NMF can effectively kill E. coli (99.99%), S. aureus (99%), and H1N1 (92.5%), meanwhile possessing good reusability. Noteworthy, the long-term use of a GZHMU-2/NWF-based mask has verified no damage to the living body by measuring the expression of mouse blood routine, lung tissue, and inflammatory factors at the in-vivo level.

3D-printed liquid metal polymer composites as NIR-responsive 4D printing soft robot

4D printing combines 3D printing with nanomaterials to create shape-morphing materials that exhibit stimuli-responsive functionalities. In this study, reversible addition-fragmentation chain transfer polymerization agents grafted onto liquid metal nanoparticles are successfully employed in ultraviolet light-mediated stereolithographic 3D printing and near-infrared light-responsive 4D printing. Spherical liquid metal nanoparticles are directly prepared in 3D-printed resins via a one-pot approach, providing a simple and efficient strategy for fabricating liquid metal-polymer composites. Unlike rigid nanoparticles, the soft and liquid nature of nanoparticles reduces glass transition temperature, tensile stress, and modulus of 3D-printed materials. This approach enables the photothermal-induced 4D printing of composites, as demonstrated by the programmed shape memory of 3D-printed composites rapidly recovering to their original shape in 60 s under light irradiation. This work provides a perspective on the use of liquid metal-polymer composites in 4D printing, showcasing their potential for application in the field of soft robots.

Two-Dimensional Cu-Porphyrin Metal-Organic Framework Nanosheet-Supported Flaky TiO2 as an Efficient Visible-Light-Driven Photocatalyst for Dye Degradation and Cr(VI) Reduction

A series of 2D M(Cu, Zn, Co, and Mn)-TCPP MOFs/TiO2 binary nanocomposites (TCPP = tetrakis(4-carboxyphenyl)porphyrin) were constructed by solvothermal in situ loading of flaky TiO2 on the surface of 2D metal-organic frameworks (MOFs). The influence of different coordination metals on the catalytic activity was studied, and it was found that the 2D Cu-TCPP MOFs/TiO2 nanocomposite exhibited the best photo-Fenton performance. The superior property can be attributed to the high absorption coefficient and ultrathin two-dimensional structure of the 2D Cu-TCPP MOFs nanosheets. Meanwhile, the 2D Cu-TCPP MOFs/TiO2 II heterostructure can effectively promote the separation and transfer of photoformed carriers. Moreover, under visible irradiation, the optimized 2D Cu-TCPP MOFs/TiO2 composite can convert 99.9% of Cr(VI) to Cr(III) within 60 min with methanol as the hole scavenger at pH 3.14. Also, the photocatalytic performance of 2D Cu-TCPP MOFs/TiO2 was maintained after five reaction cycles. Furthermore, the proposed visible-light-driven photocatalysis mechanism of the 2D Cu-MOFs/TiO2 composite was reasonably derived according to experimental results. This study demonstrates the potential of building efficient TiO2-based visible light photocatalysts with 2D metal-porphyrin MOFs.

Emulsion-Directed Synthesis of Poly-Porphyrin Nanoparticles as Heterogeneous Photocatalysts for PET-RAFT Polymerization

Heterogeneous photocatalysts have attracted extensive attention in photo-induced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization due to their remarkable advantages such as easy preparation, tunable photoelectric properties, and recyclability. In this study, zinc (II) 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (ZnTAPP)-based poly-porphyrin nanoparticles (PTAPP-Zn) are constructed by an emulsion-directed approach. It is investigated as a heterogeneous photocatalyst for PET-RAFT polymerization of various methacrylate monomers under visible light exposure, and the reactions show refined polymerization control with high monomer conversions. Furthermore, it is demonstrated that the PTAPP-Zn nanoparticles with the larger pore size enhance photocatalytic activity in PET-RAFT polymerization. In addition, the capabilities of oxygen tolerance and temporal control are demonstrated and PTAPP-Zn particles can be easily recycled and reused without an obvious decrease in catalytic efficiency.

Mesoporous Mixed-Metal-Organic Framework Incorporating a [Ru(Phen)3]2+ Photosensitizer for Highly Efficient Aerobic Photocatalytic Oxidative Coupling of Amines

[Ru(Phen)₃]²⁺ (phen = phenanthroline) as a very classical photosensitizer possesses strong absorption in the visible range and facilitates photoinduced electron transfer, which plays a vital role in regulating photochemical reactions. However, it remains a significant challenge to utilize more adequately and exploit more efficiently the ruthenium-based materials due to the uniqueness, scarcity, and nonrenewal of the noble metal. Here, we integrate the intrinsic advantages of the ruthenium-based photosensitizer and mesoporous metal-organic frameworks (meso-MOFs) into a [Ru(Phen)₃]²⁺ photosensitizer-embedded heterometallic Ni(II)/Ru(II) meso-MOF (LTG-NiRu) via the metalloligand approach. LTG-NiRu, with an extremely robust framework and a large one-dimensional (1D) channel, not only makes ruthenium photosensitizer units anchored in the inner wall of meso-MOF tubes to circumvent the problem of product/catalyst separation and recycling of catalysts in heterogeneous systems but also exhibits exceptional activities for the aerobic photocatalytic oxidative coupling of amine derivatives as a general photocatalyst. The conversion of the light-induced oxidative coupling reaction for various benzylamines is ∼100% in 1 h, and more than 20 chemical products generated by photocatalytic oxidative cycloaddition of N-substituted maleimides and N,N-dimethylaniline can be synthesized easily in the presence of LTG-NiRu upon visible light irradiation. Moreover, recycling experiments demonstrate that LTG-NiRu is an excellent heterogeneous photocatalyst with high stability and excellent reusability. LTG-NiRu represents a great potential photosensitizer-based meso-MOF platform with an efficient aerobic photocatalytic oxidation function that is convenient for gram-scale synthesis.

Design, synthesis, and application of some two-dimensional materials

Two-dimensional (2D) materials are widely used as key components in the fields of energy conversion and storage, optoelectronics, catalysis, biomedicine, etc. To meet the practical needs, molecular structure design and aggregation process optimization have been systematically carried out. The intrinsic correlation between preparation methods and the characteristic properties is investigated. This review summarizes the recent research achievements of 2D materials in the aspect of molecular structure modification, aggregation regulation, characteristic properties, and device applications. The design strategies to fabricate functional 2D materials starting from precursor molecules are introduced in detail referring to organic synthetic chemistry and self-assembly technology. It provides important research ideas for the design and synthesis of related materials.

Conjugated cross-linked phosphine as broadband light or sunlight-driven photocatalyst for large-scale atom transfer radical polymerization

The use of light to regulate photocatalyzed reversible deactivation radical polymerization (RDRP) under mild conditions, especially driven by broadband light or sunlight directly, is highly desired. But the development of a suitable photocatalyzed polymerization system for large-scale production of polymers, especially block copolymers, has remained a big challenge. Herein, we report the development of a phosphine-based conjugated hypercrosslinked polymer (PPh₃-CHCP) photocatalyst for an efficient large-scale photoinduced copper-catalyzed atom transfer radical polymerization (Cu-ATRP). Monomers including acrylates and methyl acrylates can achieve near-quantitative conversions under a wide range (450-940 nm) of radiations or sunlight directly. The photocatalyst could be easily recycled and reused. The sunlight-driven Cu-ATRP allowed the synthesis of homopolymers at 200 mL from various monomers, and monomer conversions approached 99% in clouds intermittency with good control over polydispersity. In addition, block copolymers at 400 mL scale can also be obtained, which demonstrates its great potential for industrial applications.

Nanomaterial integrated 3D printing for biomedical applications

3D printing technology, otherwise known as additive manufacturing, has provided a promising tool for manufacturing customized biomaterials for tissue engineering and regenerative medicine applications. A vast variety of biomaterials including metals, ceramics, polymers, and composites are currently being used as base materials in 3D printing. In recent years, nanomaterials have been incorporated into 3D printing polymers to fabricate innovative, versatile, multifunctional hybrid materials that can be used in many different applications within the biomedical field. This review focuses on recent advances in novel hybrid biomaterials composed of nanomaterials and 3D printing technologies for biomedical applications. Various nanomaterials including metal-based nanomaterials, metal-organic frameworks, upconversion nanoparticles, and lipid-based nanoparticles used for 3D printing are presented, with a summary of the mechanisms, functional properties, advantages, disadvantages, and applications in biomedical 3D printing. To finish, this review offers a perspective and discusses the challenges facing the further development of nanomaterials in biomedical 3D printing.

Metalloporphyrin Metal–Organic Frameworks: Eminent Synthetic Strategies and Recent Practical Exploitations

The emergence of metal–organic frameworks (MOFs) in recent years has stimulated the interest of scientists working in this area as one of the most applicable archetypes of three-dimensional structures that can be used as promising materials in several applications including but not limited to (photo-)catalysis, sensing, separation, adsorption, biological and electrochemical efficiencies and so on. Not only do MOFs have their own specific versatile structures, tunable cavities, and remarkably high surface areas, but they also present many alternative procedures to overcome emerging obstacles. Since the discovery of such highly effective materials, they have been employed for multiple uses; additionally, the efforts towards the synthesis of MOFs with specific properties based on planned (template) synthesis have led to the construction of several promising types of MOFs possessing large biological or bioinspired ligands. Specifically, metalloporphyrin-based MOFs have been created where the porphyrin moieties are either incorporated as struts within the framework to form porphyrinic MOFs or encapsulated inside the cavities to construct porphyrin@MOFs which can combine the peerless properties of porphyrins and porous MOFs simultaneously. In this context, the main aim of this review was to highlight their structure, characteristics, and some of their prominent present-day applications.

Ti3 C2 TX MXene Modified with ZnTCPP with Bacteria Capturing Capability and Enhanced Visible Light Photocatalytic Antibacterial Activity

Light-assisted antibacterial therapy is a promising alternative to antibiotic therapy due to the high antibacterial efficacy without bacterial resistance. Recent research has mainly focused on the use of near-infrared light irradiation to kill bacteria by taking advantage of the synergistic effects rendered by hyperthermia and radical oxygen species. However, photocatalytic antibacterial therapy excited by visible light is more convenient and practical, especially for wounds. Herein, a visible light responsive organic-inorganic hybrid of ZnTCPP/Ti₃ C₂ T_X is designed and fabricated to treat bacterial infection with antibacterial efficiency of 99.86% and 99.92% within 10 min against Staphylococcus aureus and Escherichia coli, respectively. The porphyrin-metal complex, ZnTCPP, is assembled on the surface of Ti₃ C₂ T_X MXene to capture bacteria electrostatically and the Schottky junction formed between Ti₃ C₂ T_X and ZnTCPP promotes visible light utilization, accelerates charge separation, and enhances the mobility of photogenerated charges, and finally increases the photocatalytic activity. As a result of the excellent bacteria capturing ability and photocatalytic antibacterial effects, ZnTCPP/Ti₃ C₂ T_X exposed to visible light has excellent antibacterial properties in vitro and in vivo. Therefore, organic-inorganic materials that have been demonstrated to possess good biocompatibility and enhance wound healing have large potential in bio-photocatalysis, antibacterial therapy, as well as antibiotics-free treatment of wounds.

Transforming Dyes into Fluorophores: Exciton-Induced Emission with Chain-like Oligo-BODIPY Superstructures

Herein we present a systematic study demonstrating to which extent exciton formation can amplify fluorescence based on a series of ethylene-bridged oligo-BODIPYs. A set of non- and weakly fluorescent BODIPY motifs was selected and transformed into discrete, chain-like oligomers by linkage via a flexible ethylene tether. The prepared superstructures constitute excitonically active entities with non-conjugated, Coulomb-coupled oscillators. The non-radiative deactivation channels of Internal Conversion (IC), also combined with an upstream reductive Photoelectron Transfer (rPET) and Intersystem Crossing (ISC) were addressed at the monomeric state and the evolution of fluorescence and (non-)radiative decay rates studied along the oligomeric series. We demonstrate that a "masked" fluorescence can be fully reactivated irrespective of the imposed conformational rigidity. This work challenges the paradigm that a collective fluorescence enhancement is limited to sterically induced motional restrictions.

Highly Effective Photocatalytic Radical Reactions Triggered by a Photoactive Metal-Organic Framework

On account of their inherent reactive properties, radical reactions play an important role in organic syntheses. The booming photochemistry provides a feasible approach to trigger the generation of radical intermediates in organic reaction processes. Thus, developing effective photocatalysts becomes the key step in radical reactions. In this work, the triphenylamine moiety with photoactivity is successfully embedded in a highly porous and stable metal-organic framework (MOF), and the obtained MOF, namely, Zr-TCA, naturally displays a photoactive property derived from the triphenylamine-based ligand. In photocatalytic studies, the triphenylamine-based Zr-TCA not only exhibits a high catalytic activity on the aerobic oxidation of sulfides via the generation of the superoxide radical anion (O2•-) under light irradiation but also shows good efficiency in the trifluoromethylation of arenes and heteroarenes by the formation of the trifluoromethyl radical (CF3•) as an intermediate. Moreover, the high performance of Zr-TCA can be well maintained over a wide range of substrates in these radical reactions, and the recycled Zr-TCA still retains its excellent photocatalytic activity. The high recyclability and catalytic efficiency to various substrates make the constructed triphenylamine-based Zr-TCA a promising photocatalyst in diverse radical reactions.

Development of High Throughput Photopolymerizations Using Micron-Sized Ultrathin Metal-Organic Framework Nanosheets

Polymer syntheses in a high throughput format are still challenging due to the tedious procedures for prior deoxygenation and catalyst removal. Two-dimensional (2D) metal-organic framework (MOF) nanosheets are advantageous for elevating the catalytic efficiency and catalyst recyclability. Polymerization of a wide variety of monomers, including hydrophilic acrylamides and hydrophobic acrylates, was attempted directly in a multi-well plate by employing Zn-ZnPPF-2D nanosheets (PPF = porphyrin paddlewheel framework) as a heterogeneous photocatalyst. Various parameters such as monomer concentration, catalyst concentration and light wavelength were investigated with respect to their effects on polymerization rate and the degree of control over the molecular weight and molecular weight distribution. Due to the larger surface area and more accessible catalytic sites, the top-performing Zn-ZnPPF-2D exhibited fast polymerization kinetics over the Zn-ZnPPF-3D bulk crystals. In addition, the synthesis of triblock copolymers with a single loading of catalysts confirmed the outstanding catalytic performance of these 2D MOF catalysts. Finally, PET-RAFT polymerization was demonstrated to be achievable entirely in a microliter-scale human cell culture medium. As such, this strategy provides high levels of control and precision over macromolecular synthesis outcomes that best align with the requirements of high throughput approaches towards biological applications. This article is protected by copyright. All rights reserved.

Controlling mechanical properties of 3D printed polymer composites through photoinduced reversible addition–fragmentation chain transfer (RAFT) polymerization

Reversible addition–fragmentation chain-transfer (RAFT) polymerization has been exploited to design silica-nanoparticle-incorporated photocurable resins for 3D printing of materials with enhanced mechanical properties and complex structures.

Metal–organic-framework-based photocatalysts for microorganism inactivation: a review

A metal–organic framework (MOF) is a porous coordination material composed of multidentate organic ligands and metal ions or metal clusters.

Porphyrin-based donor-acceptor COFs as efficient and reusable photocatalysts for PET-RAFT polymerization under broad spectrum excitation

Covalent organic frameworks (COFs) are crystalline and porous organic materials attractive for photocatalysis applications due to their structural versatility and tunable optical and electronic properties. The use of photocatalysts (PCs) for polymerizations enables the preparation of well-defined polymeric materials under mild reaction conditions. Herein, we report two porphyrin-based donor-acceptor COFs that are effective heterogeneous PCs for photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT). Using density functional theory (DFT) calculations, we designed porphyrin COFs with strong donor-acceptor characteristics and delocalized conduction bands. The COFs were effective PCs for PET-RAFT, successfully polymerizing a variety of monomers in both organic and aqueous media using visible light (λ max from 460 to 635 nm) to produce polymers with tunable molecular weights (MWs), low molecular weight dispersity, and good chain-end fidelity. The heterogeneous COF PCs could also be reused for PET-RAFT polymerization at least 5 times without losing photocatalytic performance. This work demonstrates porphyrin-based COFs that are effective catalysts for photo-RDRP and establishes design principles for the development of highly active COF PCs for a variety of applications.

Contributions of photochemistry to bio-based antibacterial polymer materials

Surgical site infections constitute a major health concern that may be addressed by conferring antibacterial properties to surgical tools and medical devices via functional coatings. Bio-sourced polymers are particularly well-suited to prepare such coatings as they are usually safe and can exhibit intrinsic antibacterial properties or serve as hosts for bactericidal agents. The goal of this Review is to highlight the unique contribution of photochemistry as a green and mild methodology for the development of such bio-based antibacterial materials. Photo-generation and photo-activation of bactericidal materials are illustrated. Recent efforts and current challenges to optimize the sustainability of the process, improve the safety of the materials and extend these strategies to 3D biomaterials are also emphasized.

Screening RAFT agents and photocatalysts to mediate PET-RAFT polymerization using a high throughput approach

We report a high throughput approach for the screening of RAFT agents and photocatalysts to mediate photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization.