Two Heterometallic-Organic Frameworks Composed of Iron(III)-Salen-Based Ligands and d10Metals: Gas Sorption and Visible-Light Photocatalytic Degradation of 2-Chlorophenol

Ultrasmall copper-metal organic framework (Cu-MOF) quantum dots decorated on waste derived biochar for enhanced removal of emerging contaminants: Synergistic effect and mechanistic insight

This study proposes a novel one-pot hydrothermal impregnation strategy for surface decoration of waste derived pisum sativum biochar with zero‒dimensional Cu‒MOF Quantum dots (PBC‒HK), with an average particle size of 5.67 nm, for synergistic removal of an emerging sulfur containing drug pantoprazole (PTZ) and Basic Blue 26 (VB) dye within 80 min and 50 min of visible-light exposure, respectively. The designed Integrated Photocatalytic Adsorbent (IPA) presented an enhanced PTZ removal efficiency of 95.23% with a catalyst loading of 0.24 g/L and initial PTZ conc. 30 mg/L at pH 7, within 80 min via synergistic adsorption and photodegradation under visible-light exposure. While, on the other hand, 96.31% VB removal efficiency was obtained in 50 min with a catalyst dosage of 0.20 g/L, initial VB conc. 60 mg/L at pH 7 under similar irradiation conditions. An in-depth analysis of the synergistic adsorption and photocatalysis mechanism resulting in the shortened time for the removal of contaminants in the synergistic integrated model has been performed by outlining the various advantageous attributes of this strategy. The first-order degradation rate constant for PTZ was found to be 0.04846 min-1 and 0.04370 min-1 for PTZ and VB, respectively. Adsorption of contaminant molecules on the biochar (PS‒BC) surface can facilitate photodegradation by accelerating the kinetics, and photodegradation promotes regeneration of adsorption sites, contributing to an overall reduction in operation time for removal of contaminants. Besides enhancing the adsorption of targeted pollutants, the carbon matrix of IPAs serves as a surface for adsorption of intermediates of degradation, thereby minimizing the risk of secondary pollution. The photogenerated holes present in the VB is responsible for the generation of •OH radicals. While, the photogenerated electrons present in the CB are captured by Cu2+ of the MOF metal center, reducing it to Cu+, which is subsequently oxidized to produce additional •OH species in the aqueous medium. This process leads to effective charge separation of the photogenerated charge carriers and minimizes the probability of charge recombination as evident from photoluminescence (PL) analysis. Meanwhile, PL studies, EPR and radical trapping experiments indicate the predominant role of •OH radicals in the removal mechanism of PTZ and VB. The investigation of the degradation reaction intermediates was confirmed by HR‒LCMS, on the basis of which the plausible degradation pathway was elucidated in detail. Moreover, effects of pH, inorganic salts, other organic compounds and humic acid concentration have been investigated in detail. The environmental impact of the proposed method was comprehensively evaluated by ICP-OES analysis and TOC and COD removal studies. Furthermore, the economic feasibility and the cost-effectiveness of the catalyst was assessed to address the potential for large scale commercialization. Notably, this research not only demonstrates a rational design strategy for the utilization of solid waste into treasure via the fabrication of IPAs based on MOF Quantum dots (QDs) and waste-derived biochar, but also provides a practical solution for real wastewater treatment systems for broader industrial applications.

Dimensional Reduction of Metal-Organic Frameworks for Photocatalytic Synthesis of Fused Tetracyclic Heterocycles

Heterogeneous palladium catalysts with high efficiency, high Pd atom utilization, simplified separation, and recycle have attracted considerable attention in the field of synthetic chemistry. Herein, we reported a zirconium-based two-dimensional metal-organic framework (2D-MOF)-based Pd(II) photocatalyst (Zr-Ir-Pd) by merging the Ir photosensitizers and Pd(II) species into the skeletons of the 2D-MOF for the Pd(II)-catalyzed oxidation reaction. Morphological and structural characterization identified that Zr-Ir-Pd with a specific nanoflower-like structure consists of ultrathin 2D-MOF nanosheets (3.85 nm). Due to its excellent visible-light response and absorption capability, faster transfer and separation of photogenerated carriers, more accessible Pd active sites, and low mass transfer resistance, Zr-Ir-Pd exhibited boosted photocatalytic activity in catalyzing sterically hindered isocyanide insertion of diarylalkynes for the construction of fused tetracyclic heterocycles, with up to 12 times the Pd catalyst turnover number than the existing catalytic systems. In addition, Zr-Ir-Pd inhibited the competitive agglomeration of Pd(0) species and could be reused at least five times, owing to the stabilization of 2D-MOF on the single-site Pd and Ir sites. Finally, a possible mechanism of the photocatalytic synthesis of fused tetracyclic heterocycles catalyzed by Zr-Ir-Pd was proposed.

Schiff base MOFs and their derivatives for sequestration and degradation of pollutants: present and future

Removal of contaminants via adsorption and catalysis have received a significant interest as energy and money-saving solutions for treating the world's wastewater. Metal-organic frameworks (MOFs), a newly discovered class of porous crystalline materials, have demonstrated tremendous promise in the removal and destruction of contaminants for water purification. In order to improve the interactions of MOFs with the target pollutants for their selective removal and degradation, the Schiff base functionalities emerged as promising active sites. Through pre- and post-synthetic alterations, Schiff base functionalities are integrated into the pore cages of MOF adsorbent materials. To understand the adsorptive/catalytic mechanism, potential interactions between the Schiff base sites and the target pollutants are discussed. Based on cutting-edge techniques for their synthesis, this paper examines current developments in the creation of Schiff base-functionalized MOFs as innovative materials for adsorptive removal and catalytic degradation of contaminants for water remediation.

Graphite oxide as an electronic conductor modified ZIF-8/NH2-MIL-125(Ti) hybrid material used as a photocatalyst for removal of organic dyes under visible light irradiation

It is a great challenge to develop photocatalysts for the degradation of organic pollutants in the aqueous environment, especially those with excellent catalytic performance under visible light conditions. In this work, using graphene oxide (GO) as an electron shuttle agent and carrier, a hybrid of ZIF-8/NH₂-MIL-125(Ti) and GO (ZIF-8/NH₂-MIL-125(Ti)/GO) was prepared by a simple two-step solvothermal method. The morphology, structure, and combination of the synthesized catalysts were studied. The results showed that graphene oxide and ZIF-8 formed an in situ load on NH₂-MIL-125(Ti). The construction of hybrid materials significantly improved the catalytic activity of NH₂-MIL-125(Ti) in the visible light range. The degradation activity of the synthesized catalyst was further tested with reactive red dye. The results showed that the catalyst exhibited excellent catalytic removal efficiency for active red, with a degradation rate of 99.8% within 2 h. The prepared hybrid materials have good application prospects in the field of organic pollutant treatment in water.

Insight into non-covalent interactions in two triamine-based mononuclear iron(iii) Schiff base complexes with special emphasis on the formation of Br⋯π halogen bonding

The nature and characteristics of noncovalent interactions that play important roles in the crystal packing of two iron(iii) complexes have been discussed.

Metal-organic frameworks based adsorbents: A review from removal perspective of various environmental contaminants from wastewater

Rapidly increasing water contamination has turned into a major threat globally. The pollutants such as organic and inorganic compounds, heavy metals, and biological organisms are among the major contributor to water pollution. Therefore, the removal of these contaminants has attracted the researchers a lot. Various methodologies are being carried out for the purpose. Among them, the metal-organic frameworks (MOFs) with several active sites and tailorable porous architectures as adsorbents or photocatalytic removal agents is a fast-growing class of coordination chemistry to remove these agents from water. To date, numerous approaches dealing with water treatment including conservative and advanced technologies have been presented. This article thoroughly reviews the application of MOFs toward how to remove the toxic agents from water. The leading objective is to present up-to-date information and references regarding MOFs based materials toward wastewater treatment applications.

Functionalized metal-organic frameworks for photocatalytic degradation of organic pollutants in environment

Currently, many kinds of organic pollutants in air and water have a negative impact on humans and the environment. Notably, as a type of new functional materials, metal-organic frameworks (MOFs) with well-ordered porous structures and numerous active sites have been proven to be ideal photocatalysts for the degradation of organic pollutants. In the past few years, many encouraging achievements have been made in the research field of MOFs for photocatalysis. And a large number of functionalized MOFs have been constructed to improve photocatalytic activity. In this review, recent progress in the photocatalytic degradation of organic pollutants in both air and water using functionalized MOFs are summarized in detail. The focus is on photocatalytic mechanisms and some strategies employed to achieve higher degradation efficiency. Furthermore, the challenges and outlooks in this promising filed are also discussed. We hope this review would be useful for designing more functionalized MOFs with greater photocatalytic performance for the degradation of organic pollutants in the environment.

Recent advances in MOF-based photocatalysis: environmental remediation under visible light

Highly photoactive MOFs can be engineered via various strategies for the purpose of extended visible light absorption, more efficient generation, separation and transfer of charge carriers, as well as good recyclability.

Water depollution using metal-organic frameworks-catalyzed advanced oxidation processes: A review

This paper presents a review on the environmental applications of metal-organic frameworks (MOFs), which are inorganic-organic hybrid highly porous crystalline materials, prepared from metal ion/clusters and multidentate organic ligands. The emphases are made on the enhancement of the performance of advanced oxidation processes (AOPs) (photocatalysis, Fenton reaction methods, and sulfate radical (SO₄^-)-mediated oxidations) using MOFs materials. MOFs act as adsorption and light absorbers, leading to superior performance of photocatalytic processes. More recent examples of photocatalytic degradation of dyes are presented. Additionally, it is commonly shown that Fe-based MOFs exhibited excellent catalytic performance on the Fenton-based and SO₄^•--mediated oxidations of organic pollutants (e.g., dyes, phenol and pharmaceuticals). The significantly enhanced generation of reactive species such as OH and/or SO₄^- by both homogeneous and heterogeneous catalysis was proposed as the possible mechanism for water depollution. Based on the existing literature, the challenge and future perspectives in MOF-based AOPs are addressed.

An in Situ Embedded Square-Planar CuII/NiIIN4 Metalloligand in Coordination Polymers for Visible-Light Photocatalysis

Three coordination polymers (CPs) with square-planar Cu^II/Ni^IIN₄ subunits were formed in one step by subcomponent self-assembly, giving rise to an unprecedented linking variety of in situ embedded metalloligands and Cu^I clusters. All CPs exhibit unusual visible-light adsorption. Enhanced photocatalytic activity and high selectivity were observed in the oxidation of benzene under visible-light irradiation.

Iron Containing Metal-Organic Frameworks: Structure, Synthesis, and Applications in Environmental Remediation

Metal-organic frameworks (MOFs) with Fe content are gradually developing into an independent branch in environmental remediation, requiring economical, effective, low-toxicity strategies to the complete procedure. In this review, recent advancements in the structure, synthesis, and environmental application focusing on the mechanism are presented. The unique structure of novel design proposed specific characteristics of different iron-containing MOFs with potential innovation. Synthesis of typical MILs, NH₂-MILs and MILs based materials reveal the basis and defect of the current method, indicating the optimal means for the actual requirements. The adsorption of various contamination with multiple interaction as well as the catalytic degradation over radicals or electron-hole pairs are reviewed. This review implied considerable prospects of iron-containing MOFs in the field of environment and a more comprehensive cognition into the challenges and potential improvement.

A direct strategy to synthesize hybrid benzothiazole–carbamate moieties via O-acylation of phenols under metal–organic framework catalysis

Cu-CPO-27 was used as an efficient recyclable catalyst for the synthesis of benzothiazole–carbamate structures.

A chiral salen-based MOF catalytic material with high thermal, aqueous and chemical stabilities

A highly stable chiral Ni(salen)-based MOF material possessing a 1D open channel can efficiently catalyze the cycloaddition of simulated industrial CO₂ with epoxides, as well as the cycloaddition of epoxides with azides and alkynes under mild conditions.

N-HO and N-HCl supported 1D chains of heterobimetallic CuII/NiII-SnIV cocrystals

The Schiff base H₂L¹ [N,N'-ethylenebis(3-methoxysalicylaldimine)] or H₂L² [N,N'-ethylenebis(3-ethoxysalicylaldimine)] was reacted with MCl₂·xH₂O and SnCl₄·5H₂O to afford the supramolecular heterobimetallic systems (H₂ED)²⁺·2[ML]·[SnCl₆]^2- [M = Cu, L = L¹ (1), L = L² (2); M = Ni, L = L¹ (3), L = L² (4); ED = 1,2-ethylenediamine], whose structures were established by single crystal X-ray analyses. Each structure includes different entities, viz. a mononuclear [CuL]/[NiL] neutral complex (coformer), a hexachlorostannate dianion [SnCl₆]^2-, a 1,2-ethylenediammonium dication (H₂ED²⁺) and, only in 2 and 4, a methanol molecule. Based on the work of Grothe et al. (Cryst. Growth Des., 2016, 16, 3237-3243), compounds 1 and 3 are cocrystal salts, 2 and 4 are cocrystal salt solvates. The ionic pairs (H₂ED)²⁺·[SnCl₆]^2- in 1-4 are encapsulated by the Cu- or Ni-complexes, and stabilized by N-HO and one N-HCl bond interactions leading to infinite 1D chains. The antimicrobial studies of 1-4 against yeasts (C. albicans and S. cerevisiae) and Gram-positive (S. aureus and E. faecalis) and -negative bacteria (P. aeruginosa and E. coli) indicate that the Ni₂Sn systems (3 and 4) are more active than the analogous Cu₂Sn ones (1 and 2).

Two heterotrimetallic organic frameworks constructed using a functionalized Schiff base ligand: syntheses, structures and visible photocatalytic activities for the degradation of chlorophenols

Two 3D heterotrimetallics have been synthesized and their photocatalytic degradation performances for chlorophenols have been investigated.

Structures and multiple properties of two polar metal–organic frameworks based on achiral N,O-coordinated ligands: toward multifunctional materials

Reported here are two polar MOFs with combined PL and SHG response or combined antiferromagnetism and photocatalysis properties.