Defective Metal Organic Framework Research Articles

Sensitizer created defective metal organic framework as a new platform for boosting visible-light photocatalysis of g-C3N4

We developed herein for the first time a sensitizer created defective MOF (SCD-MOF), simultaneously possessing sensitizers and defects as visible-light harvester and electron trapper, respectively, which can synergistically improve the visible-light photocatalysis of polymeric graphitic carbon nitride (g-C3N4). Based on this discovery, the resulting 5.0 wt% FeTCPP⊂UiO-66@g-C3N4 shows a significant 6.6 and 3.9 times improvement in catalytic efficiency compared with its parent materials of FeTCPP⊂UiO-66 and g-C3N4 in degrading organic pollutants. Moreover, it shows a 10.4 times enhancement in catalytic efficiency compared with commercial TiO2 (P25). Mechanism studies suggest that sensitizer molecules and defects in SCD-MOF can synergistically improve photocatalytic efficiency because of broadening the visible-light response and strengthening the charge carrier separation. This work illustrates a remarkably triple synergetic effect among visible-light harvester, electron/hole separator, and semiconductor and thus established SCD-MOF as a class of new platform to greatly improve the visible-light photocatalytic performance of conventional semiconductors.

Engineering NH2‐Cu‐NH2 Triple‐atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3

AbstractSelective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C−C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal–organic framework UiO‐66‐NH2 for selective overall photo‐reduction of CO2 into acetone. The Cu2+ site in well‐modified CuN2O2 units served as a trapping site to capture electrons via efficient electron‐hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*‐CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat−1 h−1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple‐atomic sites to producing C3 product from photosynthesis with water.

Engineering NH2-Cu-NH2 Triple-atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3.

Selective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C-C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal-organic framework UiO-66-NH2 for selective overall photo-reduction of CO2 into acetone. The Cu2+ site in well-modified CuN2O2 units served as a trapping site to capture electrons via efficient electron-hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*-CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat -1 h-1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple-atomic sites to producing C3 product from photosynthesis with water.

Phosphomolybdic acid regulated the defective metal-organic framework UiO-66 for electrochemical nitrogen reduction reaction

In recent years, electrochemical ammonia synthesis has been considered a green process with excellent application prospects. The nitrogen reduction process (NRR) needs more activation energy when NN bonds are broken, which decreases the ammonia yield rate and Faraday efficiency (FE) for ammonia synthesis. Herein, UiO-66-xHPMo electrocatalysts are effectively synthesized by regulating the defects of the metal-organic framework (UiO-66) using phosphomolybdic acid (HPMo) as a defect regulator. XRD, FT-IR, TEM, XPS, TPD, etc., characterized the catalysts. As a result, the reasons for the increase in NH3 yield rate (RNH3) are catalysts losing the ligand of terephthalic acid, exposing more Zr6 nodes as active sites, and providing numerous active sites for NN cleavage. However, introducing HPMo makes catalysts more alkaline and have lower charge transfer resistance, which are more inclined to adsorb H+ and enhance hydrogen evolution reaction (HER), reducing FEs. Thus, with a voltage of −0.3 V (vs. RHE) and a neutral electrolyte (0.1 mol L−1 Na2SO4), UiO-66–2HPMo has excellent NRR performance (RNH3: 36.61 μg h−1 mg−1, FE: 31.09%).

A Janus-ROS Healing System Promoting Infectious Bone Regeneration via Sono-Epigenetic Modulation.

Elimination of bacterial infections and simultaneously promoting osteogenic differentiation are highly required for infectious bone diseases. Massive reactive oxygen species (ROS) can damage cells, while low ROS concentrations as a molecular signal can regulate cellular fate. In this study, a Janus-ROS healing system is developed for infectious bone regeneration. An alendronate (ALN)-mediated defective metal-organic framework (MOF) sonosensitizer is prepared, which can effectively clear Methicillin-resistant Staphylococcus aureus (MRSA) infections and promote osteogenic differentiation under differential ultrasonic irradiation. In the presence of zirconium-phosphate coordination, the ALN-mediated porphyrin-based MOF (HN25) with a proper defect has great sonodynamic antibacterial efficiency (98.97%, 15min) and bone-targeting ability. Notably, under low-power ultrasound irradiation, HN25 can increase the chromatin accessibility of ossification-related genes and FOXO1 to promote bone repair through low ROS concentrations. Animal models of paravertebral infection, fracture with infection, and osteomyelitis demonstrate that HN25 successfully realizes the targeted and potent repair of various infectious bone tissues through rapid MRSA elimination, inhibiting osteoclast activity and promoting bone regeneration. The results show that high catalytic efficiency and bioactive MOF can be constructed using pharmaceutical-mediated defect engineering. The Janus-ROS treatment is also a promising therapeutic mode for infectious tissue regeneration.

Tuning Main Group Element-based Metal-Organic Framework to Boost Electrocatalytic Nitrogen Reduction Under Ambient Conditions.

Main group element-based materials are emerging catalysts for ammonia (NH3 ) production via a sustainable electrochemical nitrogen reduction reaction (N2 RR) pathway under ambient conditions. However, their N2 RR performances are less explored due to the limited active behavior and unclear mechanism. Here, an aluminum-based defective metal-organic framework (MOF), aluminum-fumarate (Al-Fum), is investigated. As a proof of concept, the pristine Al-Fum MOF is synthesized by the solvothermal reaction process, and the defect engineering method namely solvent-assisted linker exchange, is applied to create the defective Al sites. The defective Al sites play an important role in ensuring the N2 RR activity for defective Al-Fum. It is found that only the defective Al-Fum enables stable and effective electrochemical N2 RR, in terms of the highest production rate of 53.9µg(NH3 ) h-1 mgcat -1 (in 0.4m K2 SO4 ) and the Faradaic efficiency of 73.8% (in 0.1m K2 SO4 ) at -0.15V vs reversible hydrogen electrode) under ambient conditions. Density functional theory calculations confirm that the N2 activation can be achieved on the defective Al sites. Such sites also allow the subsequent protonation process via the alternating associative mechanism. This defect characteristic gives the main group Al-based MOFs the ability to serve as promising electrocatalysts for N2 RR and other attractive applications.

Coordination Defect-Induced Frustrated Lewis Pairs in Polyoxometalate-Based Metal-Organic Frameworks for Efficient Catalytic Hydrogenation.

Precise control of the structure and spatial distance of Lewis acid (LA) and Lewis base (LB) sites in a porous system to construct efficient solid frustrated Lewis pair (FLP) catalyst is vital for industrial application but remains challenging. Herein, we constructed FLP sites in a polyoxometalate (POM)-based metal-organic framework (MOF) by introducing coordination-defect metal nodes (LA) and surface-basic POM with abundant oxygen (LB). The well-defined and unique spatial conformation of the defective POM-based MOF ensure that the distance between LA and LB is at ~4.3 Å, a suitable distance to activate H2. This FLP catalyst can heterolytically dissociate H2 into active Hδ-, thus exhibiting high activity in hydrogenation, which is 55 and 2.7 times as high as that of defect-free POM-based MOF and defective MOF without POM, respectively. This work provides a new avenue toward precise design multi-site catalyst to achieve specific activation of target substrate for synergistic catalysis.

Coordination Defect‐Induced Frustrated Lewis Pairs in Polyoxo‐metalate‐Based Metal–Organic Frameworks for Efficient Catalytic Hydrogenation

AbstractPrecise control of the structure and spatial distance of Lewis acid (LA) and Lewis base (LB) sites in a porous system to construct efficient solid frustrated Lewis pair (FLP) catalyst is vital for industrial application but remains challenging. Herein, we constructed FLP sites in a polyoxometalate (POM)‐based metal–organic framework (MOF) by introducing coordination‐defect metal nodes (LA) and surface‐basic POM with abundant oxygen (LB). The well‐defined and unique spatial conformation of the defective POM‐based MOF ensure that the distance between LA and LB is at ~4.3 Å, a suitable distance to activate H2. This FLP catalyst can heterolytically dissociate H2 into active Hδ−, thus exhibiting high activity in hydrogenation, which is 55 and 2.7 times as high as that of defect‐free POM‐based MOF and defective MOF without POM, respectively. This work provides a new avenue toward precise design multi‐site catalyst to achieve specific activation of target substrate for synergistic catalysis.

Defective metal–organic framework derived from the waste plastic bottles for rapid and efficient nitroimidazole antibiotics removal

In order to alleviate the pressure on the ecological environment and human health caused by wastewater of nitroimidazole antibiotics and poly(ethylene terephthalate) (PET) plastic waste, we propose a strategy of using defective MIL-68(Al) (d-MIL-68(Al)) derived from waste PET plastic for dimetridazole (DMZ) capture. The resulting d-MIL-68(Al) exhibits an excellent adsorption capacity of 555.6 mg g−1, which is three times of pristine MIL-68(Al) (181.8 mg g−1), demonstrating that the defective structures in d-MIL-68(Al) play a crucial role in the adsorption process. Remarkably, d-MIL-68(Al) can remove nearly 97% of DMZ in the first 10 s, and the removal efficiency reached 99% after adsorption equilibrium, affording a record kinetic rate constant k2 (2.84 g mg−1 min−1). In short, d-MIL-68(Al) possesses both an ultrafast adsorption rate and outstanding adsorption capacity toward DMZ compared with reported adsorbents. Mechanism analysis reveals that the excellent DMZ adsorption performances can be ascribed to the abundant active sites caused by defective structures, as well as the π-π stacking and hydrogen bonding interactions between MOF and DMZ. Hence, d-MIL-68(Al) derived from waste PET plastic is an efficient porous adsorbent for rapid DMZ removal, which not only possesses great potential for wastewater treatment, but also reduces the harmful PET plastic waste, reflecting the concept of sustainable development.

Removal of bisphenol A by integrated adsorption and biodegradation using immobilized laccase onto defective PCN-224

Environmentally widespread endocrine-disrupting chemicals, such as bisphenol A (BPA), have posed a risk to living things. Laccase, a kind of oxidoreductase, can effectively catalyze the degradation of phenolic compounds like BPA. Herein, a defective metal-organic framework (dPCN-224) with BPA adsorption capability was synthesized and used for laccase immobilization. The material was extensively characterized and successful immobilization of laccase via hydrophobic interaction was confirmed. The immobilization reached an enzyme loading density of 80 mg/g onto dPCN-224 and the laccase@dPCN-224 showed high activity recovery (90.0% vs. free laccase) and increased thermostability, pH tolerance, and organic co-solvent resistance over the free enzyme. Moreover, at various concentrations (0.5–20 mg/L), the BPA removal efficiencies of laccase@dPCN-224 were 3.3–5.0 times higher than those of free laccase due to the cooperative effect of adsorption and enzymatic degradation. The BPA bound on laccase@dPCN-224 could be almost completely biodegraded by adding 0.5 mM of electro-mediator (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)). In addition, after five consecutive batch cycles, the BPA removal efficiency of laccase@dPCN-224 kept as high as 98.1% at 5 mg/L BPA. Taken together, the results proved the potential of laccase@dPCN-224 for applications in addressing environmental BPA pollutions.

Defective Metal–Organic Framework Nanocrystals as Signal Amplifiers for Electrochemical Dopamine Sensing

Defective Metal–Organic Framework Nanocrystals as Signal Amplifiers for Electrochemical Dopamine Sensing

Thiol-decorated defective metal-organic framework for effective removal of mercury(II) ion

Removal of mercury (Hg) ion from water is important while still faces challenges in capacity and adsorption speed. Herein, using thiol-containing mercaptoacetic acid (MA) as the template, we constructed a novel metal-organic framework (MOF) adsorbent, Zr-MSA-MA (MSA, mercaptosuccinic acid). Unlike other monodentate acids such as acetic acid and formic acid, MA benefits to maintain high-content binding sites, in the meantime of defect formation. On the basis, Zr-MSA-MA exhibits a high adsorption capacity of 714.8 mg g−1 for Hg2+ and fast adsorption kinetics, superior to other MOF-based adsorbents. Co-existing metal ions and pH have only slight interference for the adsorption behavior. Besides, the adsorption is proved to an endothermic reaction and the adsorbent can be regenerated based on a simple elution. Further analysis indicates the strong chemical bonding of Hg2+ and –SH is the main adsorption mechanism. Thus, our work demonstrates the Zr-MSA-MA can serve as a potential adsorbent for Hg2+, and provides a novel strategy to construct defective adsorbent via using active group-containing template.

Defective MOF-74 with ancillary open metal sites for the enhanced adsorption of chemical warfare agent simulants.

The development of effective porous adsorbents plays a vital role in eliminating hazardous substances from the environment. Toxic chemicals, including chemical warfare agents (CWAs), pose significant risks to both humans and ecosystems, highlighting the urgency to create efficient porous adsorbents. Therefore, substantial attention has been directed towards advancing adsorption techniques for the successful eradication of CWAs from the environment. Herein, we demonstrate a rational approach for enhancing the adsorption capability of a porous metal-organic framework (MOF) by employing ancillary open metal sites within the MOF structure. To generate defective MOF-74 (D-MOF-74) with ancillary open metal sites, some of the 2,5-dihydroxy-1,4-bezenedicarboxylic acid (DHBDC) linkers originally present in the MOF-74 structure were replaced with 1,4-benzenedicarboxylic acid (BDC) linkers. The absence of hydroxyl groups in the BDC linkers compared to the original DHBDC linkers creates ancillary open metal sites, which enhance the adsorption ability of D-MOF-74 for CWA simulants such as dimethyl methyl phosphonate, 2-chloroethyl ethyl sulfide, and methyl salicylate by providing effective interaction sites for the targeted molecules. However, excessive creation of open metal sites causes the collapse of the originally well-developed MOF-74 structure, resulting in a substantial reduction in its empty space and a subsequent decline in adsorption efficiency. Thus, to produce a defective MOF with the best performance, it is necessary to replace an appropriate amount of organic linker and create suitable open metal sites. Moreover, D-MOF-74 displays excellent recyclability during consecutive adsorption cycles without losing its original structure and morphology, suggesting that D-MOF-74 is an effective and stable material for the removal of CWA simulants.

Facile electrospray fabrication of ultralow biofouling cellulose acetate desalination membrane with nanocellulose/UiO66-NH2 fillers

The inherently high porosity, hydrophilicity, and large surface area of the octahedral UiO66-NH2 nanocrystals were exploited in synergy with cellulose nanocrystals (CNCs) as electrospray coating nanocomposites onto the cellulose acetate (CA) desalination membranes. Optimal loadings of both nanoparticles (0.05% w/v each) enabled the partial embedment of the defective metal-organic framework (MOF) crystals in the dense CA layer, successfully facilitating a faster, low-tortuosity water transport pathway through the active layer. With just one electrospray scan, the CNC/UiO66-NH2-coated CA membrane achieved an almost doubled the water permeability coefficient of 0.24 L m−2 h−1 bar−1 while maintaining a retention efficiency of over 94% in brackish water desalination. Moreover, the electrospray-coated membrane demonstrated healthier flux recovery from continuous E. coli cross-flow filtration exposure, exhibiting great resistance to biofouling. Overall, the CNC/UiO66-NH2-coated CA membrane outperforms many CA-based desalination membranes reported in the literature in terms of water/salt permselectivity and anti-fouling capabilities.

Enzymes-Encapsulated Defective Metal–Organic Framework Hydrogel Coupling with a Smartphone for a Portable Glucose Biosensor

Enzymes featuring high catalytic efficiency and selectivity have been widely used as the sensing element in analytical chemistry. However, the structural fragility and poor machinability of an enzyme significantly limit its practicability in biosensors. Herein, we develop a robust and sensitive hybrid biosensor by means of co-encapsulating enzymes into a defective metal-organic framework (MOF), followed by a double-crosslinked alginate gelatinization. The defective MOF encapsulation can enhance the stability of enzymes, yet well preserve their biocatalytic function, while the alginate gelatinization allows the MOF biohybrid high stretchability and mechanical strength, which facilitates the integration of a bead-, fiber-, and sheet-like portable biosensor. In this work, the enzymes consisting of glucose oxidase and peroxidase are co-encapsulated into this MOF hydrogel, and it can efficiently convert glucose into a blue-violet product through the biocatalytic cascade of encapsulated enzymes, enabling the colorimetric biosensing of glucose on a miniaturized MOF hydrogel when coupling with a smartphone. Interestingly, this MOF biohybrid hydrogel outputs a stronger sensing signal than the free biohybrid powders, attributed to the catalytic product-accumulated effect of the highly hydrophilic microenvironment of the hydrogel. As a result, this portable biosensor can sensitively and selectively sense glucose with a linear range from 0.05 to 4 mM. Importantly, both the hydrophilic hydrogel and MOF "armor" endow enzymes with high durability, and its sensing activity was well-maintained even after placing the biosensor at room temperature for 30 d. We believe that this MOF biohybrid hydrogel has huge potential for the engineering of next-generation portable biosensors.

Silver Nanoparticle-Incorporated Defect-Engineered Zr-based Metal-Organic Framework for Efficient Multicomponent Catalytic Reactions.

Small-sized silver nanoparticles are incorporated into a thiol-functionalized stable Zr-based metal-organic framework (MOF). Thiol functionalization has been carried out using 2-mercapto benzoic acid (2-MBA) as the modulator, which promotes defect formation in the MOF structure. The incorporation of silver nanoparticles aided by the silver-sulfur interactions in this defective MOF gives rise to catalytic activity. Its catalytic efficiency in the highly atom-efficient A3 coupling reaction has been studied for a variety of substrates with impressive recyclability. The synergistic effect of the electron-rich silver core and electron-deficient surface of the thiol-bonded silver nanoparticle is key for this catalytic reaction.

Breaking the Activity-Selectivity Trade-Off of Pt Nanoparticles Encapsulated in UiO-66 for Hydrogenation by Constructing Suitable Hierarchical Structure

The simultaneous enhancement of activity and selectivity during hydrogenation is a great challenge. Herein, by encapsulating Pt nanoparticles (NPs) into the hierarchical defective metal–organic framework (MOF) of UiO-66, the steric screening effect of the pores, Lewis acid sites of the nodes, and metal-MOF synergy have been finely tuned and effectively utilized for selective hydrogenation. Benefiting from optimal meso/micropores, favorable Lewis acid sites and strengthened metal–support interaction, Pt NPs encapsulated in hierarchical UiO-66 exhibited superior performance in selective hydrogenation. With the proper loading of Pt NPs into suitable meso/microporous UiO-66, the conversion of cinnamaldehyde is increased from 18.2% to 85% along with the selectivity for cinnamyl alcohol being improved from 15.8% to 76% under 70 °C and 2 MPa. The conventional trade-off relationship between increasing selectivity and promoting activity for encapsulated metal catalysts has been broken with the as-developed catalyst. This study provides a promising strategy to optimize transformation efficiency by the design of a tailored MOF-based framework for encapsulating metal NPs with the needed steric effect and synergistic effect.

Mitigated Aging in a Defective Metal–Organic Framework Pillared Polymer of an Intrinsic Porosity Hybrid Membrane for Efficient Gas Separation

Mitigated Aging in a Defective Metal–Organic Framework Pillared Polymer of an Intrinsic Porosity Hybrid Membrane for Efficient Gas Separation

Defective metal-organic framework derivative for efficient electrocatalytic oxygen evolution reaction

At present, we are still striving for sustainable and clean energy production to meet the energy demand of modern society. Among various advanced technologies, electrocatalytic oxygen evolution reaction (OER) plays a key role. Here, we have prepared Ce1-xCuxO nanorods with excellent structural properties by MOF derivation method. In this case, Ce1-xCuxO nanorods can achieve high catalytic activity, high specific surface area and abundant oxygen vacancies, and further improve the OER activity. In 1.0 M KOH, the Ce1-xCuxO electrocatalyst achieves a current density of 10 mA·cm−2 at a low overpotential of 351 mV and a Tafel slope of 82.6 mV·dec−1. Moreover, Ce1-xCuxO exhibits superior electrochemical stability. Our study provides a facile and efficient strategy for the rational design of MOF-derived materials towards effective and low-cost electrocatalysis.

Thiol-Decorated Defective Metal-Organic Framework for Effective Removal of Mercury(Ii) Ion

Thiol-Decorated Defective Metal-Organic Framework for Effective Removal of Mercury(Ii) Ion