Trap Inlaid Cationic Hybrid Composite Material for Efficient Segregation of Toxic Chemicals from Water

Ultralight crystalline hybrid composite material for highly efficient sequestration of radioiodine

Considering the importance of sustainable nuclear energy, effective management of radioactive nuclear waste, such as sequestration of radioiodine has inflicted a significant research attention in recent years. Despite the fact that materials have been reported for the adsorption of iodine, development of effective adsorbent with significantly improved segregation properties for widespread practical applications still remain exceedingly difficult due to lack of proper design strategies. Herein, utilizing unique hybridization synthetic strategy, a composite crystalline aerogel material has been fabricated by covalent stepping of an amino-functionalized stable cationic discrete metal-organic polyhedra with dual-pore containing imine-functionalized covalent organic framework. The ultralight hybrid composite exhibits large surface area with hierarchical macro-micro porosity and multifunctional binding sites, which collectively interact with iodine. The developed nano-adsorbent demonstrate ultrahigh vapor and aqueous-phase iodine adsorption capacities of 9.98 g.g-1 and 4.74 g.g-1, respectively, in static conditions with fast adsorption kinetics, high retention efficiency, reusability and recovery.

A Water-Stable Cationic SIFSIX MOF for Luminescent Probing of Cr2 O7 2- via Single-Crystal to Single-Crystal Transformation

The sensing and monitoring of toxic oxo-anion contaminants in water are of significant importance to biological and environmental systems. A rare hydro-stable SIFSIX metal-organic framework, SiF6 @MOF-1, {[Cu(L)2 (H2 O)2 ]·(SiF6 )(H2 O)}n , with exchangeable SiF6 2- anion in its pore is strategically designed and synthesized, exhibiting selective detection of toxic Cr2 O7 2- oxo-anion in an aqueous medium having high sensitivity, selectivity, and recyclability through fluorescence quenching phenomena. More importantly, the recognition and ion exchange mechanism is unveiled through the rarely explored single-crystal-to-single crystal (SC-SC) fashion with well-resolved structures. A thorough SC-SC study with interfering anions (Cl- , F- , I- , NO3 - , HCO3 - , SO4 2- , SCN- , IO3 - ) revealed no such transformations to take place, as per line with quenching studies. Density functional theory calculations revealed that despite a lesser binding affinity, Cr2 O7 2- shows strong orbital mixing and large driving forces for electron transfer than SiF6 2- , and thus enlightens the fluorescence quenching mechanism. This work inaugurates the usage of a SIFSIX MOF toward sensing application domain under aqueous medium where hydrolytic stability is a prime concern for their plausible implementation as sensor materials.

Confinement inside MOFs Enables Guest-Modulated Spin Crossover of Otherwise Low-Spin Coordination Cages

Confinement of discrete coordination cages within nanoporous lattices is an intriguing strategy to gain unusual properties and functions. We demonstrate here that the confinement of coordination cages within metal-organic frameworks (MOFs) allows the spin state of the cages to be regulated through multilevel host-guest interactions. In particular, the confined in situ self-assembly of an anionic FeII4L6 nanocage within the mesoporous cationic framework of MIL-101 leads to the ionic MOF with an unusual hierarchical host-guest structure. While the nanocage in solution and in the solid state has been known to be invariantly diamagnetic with low-spin FeII, FeII4L6@MIL-101 exhibits spin-crossover (SCO) behavior in response to temperature and release/uptake of water guest within the MOF. The distinct color change concomitant with water-induced SCO enables the use of the material for highly selective colorimetric sensing of humidity. Moreover, the spin state and the SCO behavior can be modulated also by inclusion of a guest into the hydrophobic cavity of the confined cage. This is an essential demonstration of the phenomenon that the confinement within porous solids enables an SCO-inactive cage to show modulable SCO behaviors, opening perspectives for developing functional supramolecular materials through hierarchical host-guest structures.

Ordered Macro/Microporous Ionic Organic Framework for Efficient Separation of Toxic Pollutants from Water

In case of pollutant segregation, fast mass diffusion is a fundamental criterion in order to achieve improved performance. The rapid mass transport through porous materials can be achieved by availing large open pores followed by easy and complete accessibility of functional sites. Inducing macroporosity into such materials could serve as ideal solution providing access to large macropores that offer unhindered transport of analyte and full exposure to interactive sites. Moreover, the challenge to configure the ionic-functionality with macroporosity could emerge as an unparalleled avenue toward pollutants separation. Herein, we strategized a synthetic protocol for construction of a positively charged hierarchically-porous ordered interconnected macro-structure of organic framework where the size and number of macropores can easily be tuned. The ordered macropores with strong electrostatic interaction synergistically exhibited ultrafast removal efficiency towards various toxic pollutants.

Synthesis of a Mixed-Ligand H-Bonded Cu Coordination Polymer: Exploring the pH-Dependent High Photocatalytic Degradation of Rhodamine 6G, Methyl Violet, Crystal Violet, and Rose Bengal Dyes under Room Illumination

A new mixed-ligand H-bonded coordination polymer {[Cu2(Or)2(Bimb)3]·4H2O} n (KA@CP-S) has been prepared hydrothermally using basic copper carbonate with 1,4-bis[(1H-imidazol-1-yl)methyl]benzene (Bimb) and potassium orotate (OrK) ligands. According to topological studies, KA@CP-S has a new topology with a three-connected uninodal net with point symbol (PS) {82·12}2{8}3. The KA@CP-S was employed as a catalyst for screening of a series of harmful cationic, anionic, and neutral organic dyes in contaminated water. The photocatalytic degradation study shows that it exhibits good catalytic efficiency for cationic dyes like Crystal Violet (CV, 75.8%), Methyl Violet (MV, 76.8%), and Rhodamine 6G (Rh6G, 86.5%) and Rose Bengal (RB, 76.1%), which is an anionic dye, while for a neutral dye, its catalytic efficiency is only 72% (Neutral Red) at ambient temperature. The effect of pH on photocatalytic degradation was also analyzed. The degradation experiment reveals that the detection limits of KA@CP-S for mostly catalyzed colorant concentrations in contaminated water are 0.60 ppm (CV), 0.20 ppm (RB), 0.33 ppm (MV), and 0.20 ppm (Rh6G) at pH 12, 4, and 10. The degradation of dyes follows pseudo-first-order kinetics. The excellent catalytic property and regeneration ability of KA@CP-S make it a potential and efficient future remedial material for the detection and separation of toxic dyes from wastewater contaminated by industrial effluents.