Adsorptive removal of indole and quinoline from model fuel using adenine-grafted metal-organic frameworks

Noteworthy synthesis strategies and applications of metal-organic frameworks for the removal of emerging water pollutants from aqueous environment

17 global Sustainable Development Goals (SDGs) were established through the adoption of the 2030 Agenda for Sustainable Development by all United Nations members. Clean water and sanitation (SDG 6) and industry, innovation, and infrastructure (SDG 9) are the SDGs focus of this work. Of late, various new companies delivering metal-organic frameworks (MOFs) have blossomed and moved the field of adsorption utilizing MOFs to another stage. Inside this unique circumstance, this article aims to catch recent advancements in the field of MOFs and the utilizations of MOFs relate to the expulsion of arising contaminations that present huge difficulties to water quality because of their steadiness and possible damage to environments and human wellbeing. Customary water treatment techniques regularly neglect to eliminate these poisons, requiring the advancement of novel methodologies. This study overviews engineering techniques for controlling MOF characteristics for better flexibility, stability, and surface area. A current report on MOFs gathered new perspectives that are amicably discussed in emergent technologies and extreme applications towards environmental sectors. Various applications in many fields that exploit MOFs are being fostered, including gas storage, fluid separation, adsorbents, catalysis, medication delivery, and sensor utilizations. The surface area of a wide range of MOFs ranges from 103 to 104 m2/g, which exceeds the standard permeability of several material designs. MOFs with extremely durable porosity are more significant in their assortment and variety than other classes of porous materials. The work outlines the difficulties encountered in the synthesis steps and suggests ways to make use of MOFs' value in a variety of contexts. This caters to creating multivariate systems enclosed with numerous functionalities, leading to the synthesis of MOFs that offer a synergistic blend of in-built properties and exclusive applications. Additionally, the MOF-related future development opportunities and challenges are discussed.

Synthesis of MnFe2O4/activated carbon derived from durian shell waste for removal of indole in water: Optimization, modelling, and mechanism

While durian shell is often discharged into landfills, this waste can be a potential and zero-cost raw material to synthesize carbon-based adsorbents with purposes of saving costs and minimizing environmental contamination. Indole (IDO) is one of serious organic pollutants that influence aquatic species and human health; hence, the necessity for IDO removal is worth considering. Here, we synthesized a magnetic composite, denoted as MFOAC, based on activated carbon (AC) derived from durian shell waste incorporated with MnFe2O4 (MFO) to adsorb IDO in water. MFOAC showed a microporous structure, along with a high surface area and pore volume, at 518.9 m2/g, and 0.106 cm3/g, respectively. Optimization of factors affecting the IDO removal of MFOAC were implemented by Box-Behnken design and response surface methodology. Adsorption kinetics and isotherms suggested a suitable model for MFOAC to remove IDO. MFOAC was recyclable with 3 cycles. Main interactions involving in the IDO adsorption mechanism onto MFOAC were clarified, including pore filling, n-π interaction, π-π interaction, Yoshida H-bonding, H-bonding.

Effect of biochars on the immobilization and form of Cadmium (Cd) in simulated Cd deposition of iron rich soils

Atmospheric deposition of Cd poses a serious threat to ecosystem security. Biochar is widely used for polluted soil remediation, however, whether biochar already applied to the soil can reduce the hazards of newly deposited Cd remains to be studied. Thus, an indoor cultural experiment and static adsorption method were conducted to study the isothermal and kinetic adsorption processes of three types of biochar (rice husk, rubber wood, and tobacco stem biochars) on Cd in iron rich soils and the effect of biochar on the morphological distribution of Cd in the soil and the soil pH. The results showed that the soil with biochar in our study could quickly fix "the new deposited Cd" in the soil in 3 h with the maximum adsorption capacity in rubber wood biochar-treated sample (3227.34 mg/kg）. The addition of all three biochar treatments significantly increased the soil pH and reduced the soil exchange state Cd content, with a 13.69-17.32% increase in the pH and a 13.22-54.39% reduction in the exchange state Cd content when contrasted with the control, which could promote those Cd converting into unavailable Cd (carbonate-bound form Cd, Fe-Mn oxide-bound form Cd, or residual form Cd) for crops. In summary, the addition of three kinds of biochar treatments could effectively reduce the ecological and environmental risk of soil that was contaminated by Cd and could provide a reliable theoretical basis for the effect of biochar on the improvement of the quality of soil that is contaminated by heavy metals.

Micro-paper-based analytical device decorated with metal-organic frameworks for the assay of synthetic cannabinoids in oral fluids coupled to ion mobility spectrometry

A new concept of paper-based device has been developed combining the advantages of cellulose supports and the rich surface chemistry of metal-organic frameworks (MOFs). The composite, named as NH2-UiO-66@paper, has been developed for the isolation of synthetic cannabinoid receptor agonists (SCRAs) in oral fluids, trying to mimic the interactions of those compounds with the human CB1R and CB2R receptors, mainly governed by hydrogen bonding and π-interactions with serine and histidine residues. MOF selection (UiO-66) and functionalization of the ligand (2-aminoterephthalic acid) has been done according to the following criteria: (i) water stability of the selected MOF, and (ii) promoting appropriate interactions with SCRAs due to the MOF nature. NH2-UiO-66@paper composite has been characterized in depth and the results confirmed that the material is stable at the temperature selected for thermal desorption (230 °C). Furthermore, the developed method provided appropriate precision values (RSD < 12%) and a limit of detection as low as 10 ng using ion mobility spectrometry as analytical technique. Lastly, the method has been successfully applied to the isolation of several synthetic cannabinoids from oral fluids. This method claims to be an interesting approach for expanding the combination of MOFs with sustainable support and represents a promising alternative to sophisticated and non-portable systems due to the negligible sample treatment required and the simplicity of the operation, which can be applied with screening purposes.

Simultaneous biodegradation of pyridine, indole, and ammonium along with phenol and thiocyanate by aerobic granular sludge

Aerobic granular sludge potential for concurrent biodegradation of two nitrogenous heterocyclic compounds (NHCs), i.e., pyridine and indole, and ammonia nitrogen along with phenol and thiocyanate was investigated in three sequencing batch reactors (SBRs) (R1, R2, and R3). Pyridine and indole were provided, respectively, in R1 and R2, whereas R3 was operated with a mixture of equimolar concentrations of pyridine and indole. Three concentrations of NHCs (1.0, 2.5, and 5.0 mM) were investigated to observe the impact on aerobic granules. Pyridine did not exhibit any adverse effect on the granular characteristics (volatile suspended solids of 6.00 ± 0.08 g L^-1 and sludge volume index of 37.98 ± 0.84 mL gTSS^-1) up to a concentration of 5.0 mM (402.93 ± 6.29 mg L^-1) (R1) with around 74% and >98% removal for pyridine and other pollutants (phenol, thiocyanate, and ammonia nitrogen), respectively. However, indole had a substantial adverse impact on the granular characteristics and other contaminants removal with a concentration of more than 1.0 mM (120.65 ± 4.84 mg L^-1) (R2). The current research work provides an experimental treatment methodology for the wastewater in which pyridine, indole, ammonium, phenol, and thiocyanate coexist.

Adsorptive removal of hazardous organics from water and fuel with functionalized metal-organic frameworks: Contribution of functional groups

The purification of contaminated water and fuel is very important for our sustainability. Adsorptive removal has attracted significant attention because of possible applications in industry and the rapid development of metal-organic frameworks (MOFs), which can be competitive adsorbents. In this review, the possible/competitive purification of water (contaminated with organics) and fuel (composed of S- and N-Containing compounds) via adsorption using MOFs, especially those with various functional groups (FGs), will be discussed. The contribution of FGs such as -OH, -COOH, -SO₃H, -NH₂, and -NH₃⁺ to adsorption/purification will be analyzed in detail, not only to understand the plausible adsorption mechanism but also to utilize specific FGs in adsorption. Moreover, methods for introducing FGs onto MOFs will be summarized. Finally, the prospects for both adsorption/removal and emerging fields will be suggested. Studies for practical applications in industry with shaped MOFs from inexpensive route will be important. The solution pH should be considered for the adsorption of aqueous solution. Applications of MOFs in other fields like storage/delivery and enrichment of analytes might be deeply studied.

High Capacity Oil Denitrogenation over Azine- and Tetrazine-Decorated Metal-Organic Frameworks: Critical Roles of Hydrogen Bonding

In this work, we demonstrate that rational decoration of pore walls of the metal-organic frameworks (MOFs) with azine and dihydro-tetrazine functions is a very practical strategy for high capacity removal of both neutral and basic nitrogen-containing compounds (NCCs) from model oil. Its performance is even much better than the MOFs with high surface area, open metal sites, and different functional groups such as amine, hydroxyl, carboxy, and sulfonate. For this aim, a number of isostructure functional MOFs (FMOFs) have been synthesized. Among them, TMU-5 (with formula [Zn(OBA)(BPDH)_0.5] _n·1.5DMF, where H₂OBA = 4,4'-oxybis(benzoic acid) and BPDH = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) and TMU-34 (with formula [Zn(OBA)(H₂DPT)_0.5] _n·DMF H₂DPT = 3,6-di(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine) show high affinity toward neutral and basic NCCs, respectively. Dihydro-tetrazine-decorated TMU-34 shows good affinity toward basic NCCs [pyridine (PYD) and quinoline (QUI)] because of hydrogen bonding of dihydro-tetrazine (-NH)···(N) basic NCCs. TMU-34 can adsorb about 619 and 632 mg g^-1 PYD and QUI, respectively. On the other hand, azine-methyl-functionalized TMU-5 shows very high affinity to neutral NCCs [pyrrole (PRR) and indole (IND)] owing to strong hydrogen bonding of azine-methyl (Me-C═N-N═C-Me)···(NH) neutral NCCs. TMU-5 can adsorb 518 and 578 mg g^-1 PRR and IND, respectively. These numbers are among the best reported data in this area and even reveal higher significance of the host-guest interaction when we consider moderate surface of these FMOFs. These results have been achieved by our "application-directed cavity functionalization" approach through decoration of MOF structures by suitable organic functional groups for specific purposes.

Polyaniline-Encapsulated Metal-Organic Framework MIL-101: Adsorbent with Record-High Adsorption Capacity for the Removal of Both Basic Quinoline and Neutral Indole from Liquid Fuel

Polyaniline-encapsulated metal-organic frameworks (MOFs; MIL-101, Cr-benzenedicarboxylate) were prepared via a ship-in-bottle strategy and applied in liquid phase adsorptions. The modified MIL-101s showed record-high adsorptions for both basic and neutral nitrogen-containing compounds (NCCs) from liquid model fuel. For example, the maximum adsorption capacities ( Q_o) of the protonated polyaniline (pANI)@MIL-101 for the basic quinoline and neutral indole from n-octane were 556 and 602 mg/g, respectively. The plausible adsorption mechanisms such as hydrogen bonding, acid-base interaction, and cation-π interaction were proposed to explain the extraordinary adsorptions of the studied adsorbates. Moreover, the adsorbents could be recycled via a simple approach and reused in adsorptions without noticeable decrease in performances. Therefore, the pANI-encapsulated MOFs could be recommended as a new type of adsorbents for very efficient removal of both basic and neutral NCCs from liquid fuel.

Uracil grafted imine-based covalent organic framework for nucleobase recognition

An imine-based covalent organic framework (COF) decorated in its cavities with uracil groups has shown selective recognition towards adenine in water.