Light-responsive Metal-organic Framework Research Articles

Efficient antibiotic degradation catalyzed by oxygen vacancy and Cu-Doped Cu-MOF under visible light

The widespread use of antibiotics in contemporary healthcare has led to their accumulation in natural water systems, contributing to a growing resistance among bacteria and posing a significant challenge to the sustainable development of human society. Photocatalysis has emerged as an effective technique to mitigate antibiotic pollution in water. This study focuses on developing and synthesizing a visible light responsive metal–organic framework (MOF), Cu-NTC, which employs copper as the metal node instead of the usual choice of molybdenum, and the rigid 1,4,5,8-naphthalene tetracarboxylic acid (H4NTC) as the organic ligand. A pivotal step in the synthesis involved the partial reduction of Cu2+, leading to the formation of Cu0/Cu+ doping. This doping, together with oxygen vacancies (OVs), introduces a localized state that functions as a doped energy level, thus prolonging carrier lifetime and enhancing the visible light photocatalytic activity of Cu-NTC. Remarkably, Cu-NTC achieved photocatalytic degradation efficiencies of 84.5 % for tetracycline (TC) and 96.1 % for norfloxacin (NFX) after 30 min in darkness followed by 120 min under visible light exposure. Moreover, Cu-NTC exhibited effective removal capabilities for other antibiotics within the quinolone and tetracycline groups, underscoring their potential for broader applications in water purification.

Versatile Multi-Wavelength Light-Responsive Metal-Organic Frameworks Micromotor through Porphyrin Metalation for Water Sterilization.

Traditional metal-organic frameworks (MOFs) based micro/nanomotors (MOFtors) can achieve three-dimensional (3D) motion mainly depending on noble metal (e.g., Pt), toxic fuels (e.g., hydrogen peroxide), and surfactants, or under external magnetic fields. In this study, light-driven MOFtors are constructed based on PCN-224(H) and regulated their photothermal and photochemical properties responding to the light of different wavelengths through porphyrin metalation. The resulting PCN-224(Fe) MOFtors presented a strong 3D motion at a maximum speed of 1234.9 ± 367.5µm s-1 under visible light due to the various gradient fields by the photothermal and photochemical effects. Such MOFtors exhibit excellent water sterilization performance. Under optimal conditions, the PCN-224(Cu) MOFtors presented the best antibacterial performance of 99.4%, which improved by 23.4% compared to its static counterpart and 43.7% compared to static PCN-224(H). The underlying mechanism demonstrates that metal doping could increase the production of reactive oxygen species (ROS) and result in a more positive surface charge under light, which are short-distance effective sterilizing ingredients. Furthermore, the motion of MOFtors appears very important to extend the short-distance effective sterilization and thus synergistically improve the antibacterial performance. This work provides a new idea for preparing and developing light-driven MOFtors with multi-responsive properties.

Significantly boosted photoelectrochemical water splitting performance by plasmonic enhanced Hematite@MOF composite photoelectrodes

Hematite as a catalyst for photoelectrochemical water splitting offers huge potential, due to its high chemical stability, great abundance, and low cost. However, the low water oxidation kinetics and poor charge transportation have hindered progress towards the manufacture of practical water splitting devices. To tackle these problems, a visible light responsive metal-organic framework (MOF) polyhedral zeolitic imidazolate (ZIF-67), and optimised plasmonic Ag nanorods were incorporated into hematite nanostructures to form a three-component heterojunction photoelectrode. The designed photoanode showed dramatically improved light harvesting in the visible range and enhanced charge transport. A mechanistic investigation allowed the deconvolution of the enhanced performance pathways. First, the Hematite@ZIF-67 core-shell p-n junction enables facile charge carrier transfer between ZIF-67 and hematite. In addition, ZIF-67 also provides active sites for water oxidation and boosts surface oxygen evolution reaction (OER) kinetics. Guided by finite-difference time-domain (FDTD) modelling, Ag nanorods with optimised aspect ratio were incorporated between ZIF-67 and hematite. The Ag nanorods facilitate broadband light absorption and surface charge injection, induced by near-field excitation enhancement and plasmonic resonance energy transfer (PRET) pathways. The design and addition of ZIF-67 and Ag nanorods result in superior performance for a hematite-based photoanode for photoelectrochemical (PEC) water oxidation.

Maintaining the configuration of a light-responsive metal–organic framework: LiYGeO4:Bi3+-incorporation-induced long-term bending through short-time light irradiation

After UV illumination at 254 nm for 10 min, the incorporated LiYGeO4:Bi3+ in the PCN-PLM can continuously provide light irradiation at 365 nm to regulate the CO2 adsorption capacity of PCN-250.

Photo-responsive metal–organic frameworks – design strategies and emerging applications in photocatalysis and adsorption

The emergence of light-responsive metal–organic frameworks represents an opportunity for stimuli responsive platform design for environmental applications.

Smart metal-organic framework (MOF) composites and their applications in environmental remediation

The applications of stimuli-responsive metal-organic frameworks (MOFs) during environmental remediation are discussed in detail in this paper. MOFs are highly porous materials with generally high adsorption capacity of environmental pollutants. The incorporation of stimuli-responsive moieties in their structures confer them with additional properties such as being easily recovered and recyclability. Consequently, there is an increase in the use of stimuli-responsive MOFs during environmental remediation. Some researchers have successfully incorporated photoactive species into the structures of MOFs resulting in the formation of light-responsive composites. The presence of thermo-responsive polymeric units in the structure of an MOF make it to have physicochemical properties that are sensitive to temperature changes. The recovery of MOFs composites can be facilitated by the incorporation of magnetic nanoparticles into their structures. This review explores the utilisation of thermo-responsive MOFs, light-responsive MOFs and magnetic responsive MOFs during environmental remediation. In addition, challenges associated with the use of smart MOFs during the remediation of polluted environments are discussed in detail in this review as well as their future prospects. • Smart MOFs are efficient adsorbents for environmental remediation • Their physicochemical properties are responsive to stimuli • Light, temperature, and magnetic stimulations are usually involved in smart MOFs • Adsorption/desorption processes in smart MOFs are triggered by changes in stimuli • Smart MOF=based membranes have stimuli-regulated pore sizes

Light-responsive metal-organic framework sheets constructed smart membranes with tunable transport channels for efficient gas separation.

Exploring a new type of smart membrane with tunable separation performance is a promising area of research. In this study, new light-responsive metal–organic framework [Co(azpy)] sheets were prepared by a facile microwave method for the first time, and were then incorporated into a polymer matrix to fabricate smart mixed matrix membranes (MMMs) applied for flue gas desulfurization and decarburization. The smart MMMs exhibited significantly elevated SO2(CO2)/N2 selectivity by 184(166)% in comparison with an unfilled polymer membrane. The light-responsive characteristic of the smart MMMs was investigated, and the permeability and selectivity of the Co(azpy) sheets-loaded smart MMMs were able to respond to external light stimuli. In particular, the selectivity of the smart MMM at the Co(azpy) content of 20% for the SO2/N2 system could be switched between 341 and 211 in situ irradiated with Vis and UV light, while the SO2 permeability switched between 58 Barrer and 36 Barrer, respectively. This switching influence was mainly ascribed to the increased SO2 adsorption capacity in the visible light condition, as verified by adsorption test. The CO2 permeability and CO2/N2 selectivity of MMMs in the humidified state could achieve 248 Barrer and 103.2, surpassing the Robeson's upper bound reported in 2019.

Facile integration of Ni-substituted polyoxometalate catalysts into mesoporous light-responsive metal-organic framework for effective photogeneration of hydrogen

The integration of functional homogeneous polyoxometalate (POM) complexes into highly-dispersed and recyclable heterogeneous catalysts remains a substantially challenging research topic in solar-driven water splitting area. In this work, we report a facile and broad-spectrum impregnation method to construct two POM@MOF composites, Ni3PW10@NU-1000 and Ni3P2W16@NU-1000, by respectively incorporating a tri-Ni-substituted Keggin-type (K6Na[Ni3(H2O)3PW10O39H2O], denoted as K6Na-Ni3PW10) and a Wells-Dawson-type (Na4Li5[Ni3(OH)3(H2O)3P2W16O59], denoted as Na4Li5-Ni3P2W16) polyoxometalate into a mesoporous Zr-based metal-organic framework (NU-1000). Under minimally optimized conditions, the resulting POM@MOF composites can effectively photocatalyze hydrogen production with superior long-term stability and reusability, achieving a hydrogen evolving rate of 3482 and 13051 μmol g−1 h−1 for Ni3PW10@NU-1000 and Ni3P2W16@NU-1000, respectively. Various photophysical and spectroscopic analyses elucidated the possible photocatalytic mechanism and the catalytic difference between two POM@MOF composites.

Controllable CO2 Capture in Metal–Organic Frameworks: Making Targeted Active Sites Respond to Light

Light-responsive metal–organic frameworks (LMOFs) are intriguing materials for CO2 capture owing to their tunable structures and performances. However, conventional LMOFs are reported to regulate C...

Linker defect engineering for effective reactive site formation in metal–organic framework photocatalysts with a MIL-125(Ti) architecture

Introduction of linker defects in a visible light responsive metal–organic framework (MOF) photocatalyst, MIL-125(Ti)–NH2, has been attempted to improve its reactivity. MIL-125(Ti)–NH2, composed of Ti-oxo cluster and 2-aminoterephthalic acid organic linker, was synthesized by a solvothermal method and then underwent photothermal treatments. XRD measurements and 1H NMR spectroscopy revealed that linker elimination from the MOF occurred by a simultaneous visible-light irradiation and mild heating at 313 K in water containing electron donor, while keeping its framework structure. The resultant defective MOF effectively promotes visible light-driven H2 evolution reaction from water containing electron donor without using any cocatalysts, and its activity is comparable to that of Pt cocatalysts-loaded crystalline MIL-125(Ti)–NH2. When pristine MIL-125(Ti)–NH2 without cocatalysts is used in the reaction, the reduction of Ti species in Ti-oxo clusters from Ti4+ to Ti3+ takes place instead of reducing protons to evolve H2; thereby, linker defect introduction caused by the photothermal treatment was concluded to play a role in creating effective reaction sites for proton reduction on Ti-oxo clusters.

A Light-Responsive Metal-Organic Framework Hybrid Membrane with High On/Off Photoswitchable Proton Conductivity.

Mimicking biological proton pumps to achieve stimuli-responsive protonic solids has long been of great interest for their diverse applications in fuel cells, chemical sensors, and bio-electronic devices. Now, dynamic light-responsive metal-organic framework hybrid membranes can be obtained by in situ encapsulation of photoactive molecules (sulfonated spiropyran, SSP), as the molecular valve, into the cavities of the host ZIF-8. The configuration of SSP can be changed and switched reversibly in response to light, generating different mobile acidic protons and thus high on/off photoswitchable proton conductivity in the hybrid membranes and device. This device exhibits a high proton conductivity, fast response time, and extremely large on/off ratio upon visible-light irradiation. This approach might provide a platform for creating emerging smart protonic solids with potential applications in the remote-controllable chemical sensors or proton-conducting field-effect transistors.

Light-Responsive Metal-Organic Framework as an Oxidase Mimic for Cellular Glutathione Detection.

Nanomaterials with enzyme-like characteristics (nanozymes) have been developed to mimic enzymes because of their low cost, high stability, and large-scale production. By using light as an external stimulation, one can modulate nanozymes' catalytic activities with controlled spatial and temporal precision. A few inorganic photoactive materials have been investigated to construct light-responsive oxidase-like nanozymes. However, these materials suffered from limited absorbance of visible light. To address this challenge, herein we have developed a photosensitized metal-organic framework (PSMOF) by using a derivative of Ru(bpy)32+ with stronger visible-light absorption as a PS linker. The PSMOF exhibited excellent oxidase-like activity, which could be modulated by switching light on and off. Moreover, the PSMOF was used to detect glutathione levels in both normal and cancer cells with good selectivity and high sensitivity. This study not only provides a smart strategy to modulate nanozymes' activities but also broadens the sensing applications of nanozymes.

New Azo-DMOF-1 MOF as a Photoresponsive Low-Energy CO2 Adsorbent and Its Exceptional CO2/N2 Separation Performance in Mixed Matrix Membranes.

A new generation-2 light-responsive metal-organic framework (MOF) has been successfully synthesized using Zn as the metal source and both 2-phenyldiazenyl terephthalic acid and 1,4-diazabicyclo[2.2.2]octane (DABCO) as the ligands. It was found that Zn-azo-dabco MOF (Azo-DMOF-1) exhibited a photoresponsive CO2 adsorption both in static and dynamic condition because of the presence of azobenzene functionalities from the ligand. Further application of this MOF was evaluated by incorporating it as a filler in a mixed matrix membrane for CO2/N2 gas separation. Matrimid and polymer of intrinsic microporosity-1 (PIM-1) were used as the polymer matrix. It was found that Azo-DMOF-1 could enhance both the CO2 permeability and selectivity of the pristine polymer. In particular, the Azo-DMOF-1-PIM-1 composite membranes have shown a promising performance that surpassed the 2008 Robeson Upper Bound.

Matrimid-JUC-62 and Matrimid-PCN-250 mixed matrix membranes displaying light-responsive gas separation and beneficial ageing characteristics for CO2/N2 separation

The performance of two generation-3 light-responsive metal-organic framework (MOF), namely JUC-62 and PCN-250, was investigated in a mixed matrix membrane (MMM) form. Both of them were incorporated inside the matrimid as the polymer matrix. Using our custom-designed membrane testing cell, it was observed that the MMMs showed up to 9% difference in CO2 permeability between its pristine and UV-irradiated condition. This shows that the light-responsive ability of the light-responsive MOFs could still be maintained. Thus, this finding is applicable in designing a smart material. Apart from that, the MMMs also has the potential to be applied for post-combustion carbon capture. At loadings up to 15 wt%, both CO2 permeability and CO2/N2 ideal selectivity could be significantly improved and surpassed the value exhibited by most of the MOF-matrimid MMM. Lastly the long term performance of the MMM was also evaluated and it was observed that both MMM could maintain their performance up to 1 month with only a slight decrease in CO2 permeability observed for 10 wt% PCN-250-matrimid. This study then opens up the possibility to fabricate a novel anti-aging multifunctional membrane material that is applicable as a smart material and also in post combustion carbon capture applications.

Light responsive metal-organic frameworks as controllable CO-releasing cell culture substrates.

A new carbon monoxide (CO)-releasing material has been developed by embedding a manganese carbonyl complex, MnBr(bpydc)(CO)3 (bpydc = 5,5'-dicarboxylate-2,2'-bipyridine) into a highly robust Zr(iv)-based metal-organic framework (MOF). Efficient and controllable CO-release was achieved under exposure to low intensity visible light. Size-controllable nanocrystals of the photoactive MOF were obtained and their CO-releasing properties were correlated with their crystal sizes. The photoactive crystals were processed into cellular substrates with a biocompatible polymer matrix, and the light-induced delivery of CO and its subsequent cellular uptake were monitored using a fluorescent CO-probe. The results discussed here demonstrate a new opportunity to use MOFs as macromolecular scaffolds towards CO-releasing materials and the advantage of MOFs for high CO payloads, which is essential in future therapeutic applications.

Photo-responsive MOFs: light-induced switching of porous single crystals containing a photochromic diarylethene

Herein we report the synthesis and characterization of light responsive metal organic framework (MOF) single crystals containing the photochromic diarylethene 1,2-bis(2,5-dimethyl-thien-3-yl)perfluorocyclopentene. Polarized light microscopy on single crystals indicates that the photochrome is preferentially aligned along the c-axis of the host.