One-pot synthesis of nitrogen-rich aminal- and triazine-based hierarchical porous organic polymers with highly efficient iodine adsorption

Exploration of iodine adsorption performance of pyrene-based two-dimensional covalent organic frameworks

Radioiodine (mainly 129I and 131I) is known to be dangerous nuclear waste due to its high toxicity, fast mobility and long radioactive half-life. As an emerging class of novel porous organic polymers, covalent organic frameworks (COFs) have demonstrated tremendous application potential in the field of radioactive iodine capture because of their high specific surface area and tunable pore structure. Herein, three π-conjugated pyrene-based COFs, namely PyTTA-BPDA-COF, PyTTA-BPY-COF, and PyTTA-BT-COF, have been successfully prepared and used as highly efficient adsorbents for iodine capture. The experimental results show that the three COFs displayed excellent adsorption performance, with adsorption capacity of 5.03, 4.46, and 3.97 g g-1 for PyTTA-BPDA-COF, PyTTA-BPY-COF, and PyTTA-BT-COF, respectively. Additionally, the release rate of iodine-loaded COFs in methanol solution and recyclability were also impressive, demonstrating their potential for practical applications. The mechanism investigation reveals that both imine linkage and π-conjugated structure of the COFs may contribute to their high iodine adsorption capability. This work is instructive as a guide for designing and synthesizing COFs as a solid-phase adsorbent for iodine uptake.

Amino-Functionalized NDI-Based MOFs as Unusual "Turn On" and "Turn Off" Fluorescent Sensors for Phenolic Pollutants with Double Solvent Channel Response and Iodine Adsorbents

Regulating mixed ligands to change the functional properties of metal-organic frameworks (MOFs) has been an important topic; especially, the structural changes have significant implications for the transformation of sensing response in different solvent channels. Herein, two [Cd (DPNDI) (NH2-BDC)0.5(NO3)]·2.25DMF (1) and [Cd(DPNDI)(NH2-AIPA)]·0.5DMF (2) (DPNDI = N,N-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide, NH2-BDC = 2-amino terephthalic acid, NH2-AIPA = 5-aminoisophthalic acid) were synthesized by the solvothermal method. Structural analysis shows that complex 1 has a two-dimensional planar network structure and complex 2 exhibits a three-dimensional network structure, endowing its potential as an efficient fluorescence sensor for phenolic compound detection under different solvent environments. Both complexes showed high fluorescence quenching sensitivity to phenolics in a water medium. Conversely, complex 1 showed a fluorescence enhancement response to phenolic pollutants in an ethanol system with significantly low detection limits and recyclability. The detection limits were 0.58 μM for TNP, 1.3 μM for DNP, and 2.43 μM for PCP. In addition, the uncoordinated amino groups in the complexes promote them to exhibit excellent iodine adsorption performance. Especially, complex 2 can serve as an adsorbent for iodine in cyclohexane solution with better adsorption efficiency than that of complex 1, and its adsorption capacity can reach 505 mg/g. The mixed ligands regulation strategy of NDI-based MOFs will open up an effective avenue for the conversion of fluorescence signals in dual-solvent channels and play simultaneously important roles in multiple applications.

Synthesis and Characterization of Bipyridine-Based Polyaminal Network for CO2 Capture

The response to the high demand for decreasing the amount of CO₂ in the atmosphere, a new polyaminal-based polymer network was designed and successfully prepared through one-pot polycondensation reaction of melamine and [2,2′-Bipyridine]-5,5′-dicarbaldehyde. The formation of the polymer structure was confirmed by FT-IR, solid-state ¹³C NMR, and powder-X-ray diffraction. The porous properties of the polymeric structure were confirmed by field-emission scanning electron microscope and N₂ adsorption–desorption methods at 77 K. The prepared polymer can take up 1.02 mmol/g and 0.71 mmol/g CO₂ at 273 K and 298 K, respectively, despite its relatively modest Brunauer–Emmett–Teller (BET) surface area (160.7 m²/g), due to the existence of superabundant polar groups on the pore surfaces.

Synthesis of Naphthalene-Based Polyaminal-Linked Porous Polymers for Highly Effective Uptake of CO2 and Heavy Metals

Studying the effect of functional groups on the porosity structure and adsorption efficiency of polymer materials is becoming increasingly interesting. In this work, a novel porous polyaminal-linked polymer, based on naphthalene and melamine (PAN-NA) building blocks, was successfully synthesized by a one-pot polycondensation method, and used as an adsorbent for both CO2 and heavy metals. Fourier transform infrared spectroscopy, solid-state 13 C NMR, powder X-ray diffraction, and thermogravimetry were used to characterize the prepared polymer. The porous material structure was established by field-emission scanning electron microscope and N2 adsorption-desorption methods at 77 K. The polymer exhibited excellent uptake of CO2, 133 mg/g at 273 K and 1 bar. In addition, the adsorption behavior of PAN-NA for different metal cations, including Pb(II), Cr(III), Cu(II), Cd(II), Ni(II), and Ba(II), was investigated; a significant adsorption selectivity toward the Pb(II) cation was detected. The influence of pH, adsorbent dose, initial concentrations, and contact time was also assessed. Our results prove that the introduction of naphthalene in the polymer network improves the porosity and, thus, CO2 adsorption, as well as the adsorption of heavy metals.

Construction of manganese-based metal organic frameworks derived from aromatic dicarboxylic acids and application for the adsorption of iodine

In this work, we selected terephthalic acid or 2-amino-terephthalic acid as ligand, transition metal manganese salt as metal source under the solvothermal conditions to successfully construct two kinds of manganese-based metal-organic frameworks (Mn-MOFs): Mn3(BDC)3(H2O)2 (1) and Mn3(NH2-BDC)3(DMF)4 (2) (H2BDC = terephthalic acid; NH2-BDC = 2-amino terephthalic acid; DMF = N, N-dimethyl formamide). It was characterized by elemental analysis, IR spectrum, thermogravimetric analysis (TG), X-ray powder diffraction (PXRD) and UV-vis absorption spectrum. It was found that the packing structures of compounds 1 and 2 were constructed by the trinuclear Mn3O16 building block and exhibited different spatial structure: compound 1 was a three-dimensional structure, and 2 was a two-dimensional network structure. The iodine adsorption in cyclohexane solution properties of compounds 1 and 2 were investigated. Research results showed that the uncoordinated amino group in the structure of framework compounds has a great influence on the iodine adsorption capacity and compound 2 had good adsorption property and reusability.

Interface assembly of specific recognition gripper wrapping on activated collagen fiber for synergistic capture effect of iodine

Efficient capture of radioactive iodine (¹²⁹I, ¹³¹I) is of great significance in spent fuel treatment. In this paper, a new adsorbent named Catechin@ACF was successfully prepared through interface assembly of specific recognition gripper with plant polyphenols (catechin) on activated collagen fiber (ACF), and the catechin membrane with specific grip on iodine was successfully constructed on the surface of ACF. The results showed that the adsorbent assembled catechin membrane was rich in aromatic rings, hydroxyl groups and imine adsorption sites, and possessed specific recognition and capture characteristics of iodine. Moreover, the as-prepared Catechin@ACF showed excellent capture capacity for iodine vapor and iodine in organic solution with the maximum capture capacity of 2122.68 mg/g and 258.29 mg/g, respectively. In iodine-cyclohexane solution, the adsorption process was in according with the Pseudo first order kinetic and Langmuir isothermal model. In addition, the specific recognition and capture mechanism analysis indicated that the aromatic rings, phenolic hydroxyl groups and imine groups in the catechin membrane were the specific and effective grippers for iodine, and finally iodine formed a stable conjugated system with the adsorbent in the form of I^- and I₃^-. Therefore, the as-prepared specific iodine capturer Catechin@ACF was expected to play a vital role in the capture of radioactive iodine in spent fuel off-gas because of its specific recognition, high capture capacity, large-scale preparation, and environment-friendly.

Porous Organic Polymer Synthesized by Green Diazo-Coupling Reaction for Adsorptive Removal of Methylene Blue

A porous organic polymer (marked as DT-POP), which contains abundant free phenolic hydroxyl groups, is synthesized by the well-known green azo-coupling reaction in water, characterized, and utilized as an effective adsorbent for the elimination of methylene blue (MB) from water solutions. The presence of permanent mesopores, abundant active functional groups, and π-electron enrichment ascribed to phenyl rings make DT-POP an efficient adsorbent for MB due to strong hydrogen bonding, π-π, and electrostatic interactions with the cationic dye MB. DT-POP with high stability and high adsorption capacity can be reused many times and thus shows high applicability in pollutant disposal.