The scientific community has been developing promising materials to increase the sustainability and efficiency of production processes and pollutant environmental remediation strategies. Porous organic polymers (POPs) are of special interest, as they are insoluble custom-built materials at the molecular level, endowed with low densities and high stability, surface areas, and porosity. This paper describes the synthesis, characterization, and performance of three triazine-based POPs (T-POPs) in dye adsorption and Henry reaction catalysis. T-POPs were prepared by a polycondensation reaction between melamine and a dialdehyde (terephthalaldehyde (T-POP1) or isophthalaldehyde derivatives with a hydroxyl group (T-POP2) or both a hydroxyl and a carboxyl group (T-POP3)). The crosslinked and mesoporous polyaminal structures, with surface areas between 139.2 and 287.4 m² g⁻¹, positive charge, and high thermal stability, proved to be excellent methyl orange adsorbents, removing the anionic dye with an efficiency >99% in just 15–20 min. The POPs were also effective for methylene blue cationic dye removal from water, reaching efficiencies up to ca. 99.4%, possibly due to favorable interactions via deprotonation of T-POP3 carboxyl groups. The modification of the most basic polymers, T-POP1 and T-POP2, with copper(II) allowed the best efficiencies in Henry reactions catalysis, leading to excellent conversions (97%) and selectivities (99.9%).

Starch is one of the most abundant polysaccharides in nature and has a high potential for application in several fields, including effluent treatment as an adsorbent. Starch has a unique structure, with zones of different crystallinity and a glycosidic structure containing hydroxyl groups. This configuration allows a wide range of interactions with pollutants of different degrees of hydrophilicity, which includes from hydrogen bonding to hydrophobic interactions. This review article aims to survey the use of starch in the synthesis of diverse adsorbents, in forms from nanoparticles to blends, and evaluates their performance in terms of amount of pollutant adsorbed and removal efficiency. A critical analysis of the materials developed, and the results obtained is also presented. Finally, the review provides an outlook on how this polysaccharide can be used more effectively and efficiently in remediation efforts in the near future.

A chitosan–silica hybrid aerogel was synthesized and presented as a potential adsorbent for the purification of cupric ion-contaminated media. The combination of the organic polymer (chitosan), which can be obtained from fishery wastes, with silica produced a mostly macroporous material with an average pore diameter of 33 µm. The obtained aerogel was extremely light (56 kg m⁻³), porous (96% porosity, 17 cm³ g⁻¹ pore volume), and presented a Brunauer–Emmett–Teller surface area (S_BET) of 2.05 m² g⁻¹. The effects of solution pH, aerogel and Cu(II) concentration, contact time, and counterion on cupric removal with the aerogel were studied. Results showed that the initial pH of the cation-containing aqueous solution had very little influence on the removal performance of this aerogel. According to Langmuir isotherm, this material can remove a maximum amount of ca. 40 mg of cupric ions per gram and the kinetic data showed that the surface reaction was the rate-limiting step and equilibrium was quickly reached (in less than one hour). Thus, the approach developed in this study enabled the recovery of waste for the preparation of a novel material, which can be efficiently reused in a new application, namely water remediation.

Toxic heavy metals are priority pollutants in wastewater, commonly present in dangerous concentrations in many places across the globe. Although in trace quantities copper is a heavy metal essential to human life, in excess it causes various diseases, whereby its removal from wastewater is a necessity. Among several reported materials, chitosan is a highly abundant, non-toxic, low-cost, biodegradable polymer, comprising free hydroxyl and amino groups, that has been directly applied as an adsorbent or chemically modified to increase its performance. Taking this into account, reduced chitosan derivatives (RCDs 1–4) were synthesised by chitosan modification with salicylaldehyde, followed by imine reduction, characterised by RMN, FTIR-ATR, TGA and SEM, and used to adsorb Cu(II) from water. A reduced chitosan (RCD3), with a moderate modification percentage (43%) and a high imine reduction percentage (98%), proved to be more efficient than the remainder RCDs and even chitosan, especially at low concentrations under the best adsorption conditions (pH 4, R_S/L = 2.5 mg mL⁻¹). RCD3 adsorption data were better described by the Langmuir–Freundlich isotherm and the pseudo-second-order kinetic models. The interaction mechanism was assessed by molecular dynamics simulations, showing that RCDs favour Cu(II) capture from water compared to chitosan, due to a greater Cu(II) interaction with the oxygen of the glucosamine ring and the neighbouring hydroxyl groups.

This study purposes three triazine-based porous organic polymers (T-POPs 1-3) as advanced platforms for the early detection of antibiotic-polluted environments and effective water decontamination, in order to mitigate water pollution and antimicrobial resistance, which are two huge current problems damaging ecosystems and human health. T-POPs exhibited good performances as adsorbents for the removal of sulfamethazine (SMT) and tetracycline (TC) from water, with efficiencies up to 97% and 96%, and maximum adsorption capacities between (0.36-0.44) and (0.21-0.27) mmol g^-1, respectively, which are similar or even higher (up to 40.3 times) than those reported for other materials. In addition, good reusability was achieved, particularly for T-POP2, despite being the polymer with the lowest surface area. A slightly higher selectivity of T-POPs for sulfonamides and the best performance of T-POP3 to remove six antibiotics from a micromolar solution were observed. T-POPs also acted as fluorescent chemosensors, since T-POP1 underwent linear Stern-Volmer fluorescence quenching in the presence of both SMT and TC, while the enhanced-fluorescent T-POP2 and T-POP3 experienced fluorescence extinction through a sphere of action mechanism in contact with TC, and bathochromic shift accompanied by a hyperchromic effect on the new fluorescent region with the increase in SMT concentration. Thus, T-POP2 and T-POP3 can both promote a selective on-site monitoring of each drug in contaminated water streams and an efficient water remediation, thanks to the synergy between hydrogen and van der Waals interactions. In summary, these triazine-based porous organic polymers are promising materials for the simultaneous monitoring and treatment of antibiotic-containing water and wastewaters.

Poly(vinyl alcohol) (PVA) hydrogels incorporating β-cyclodextrin (βCD) nanosponges (CDNSs) were developed as hybrid supramolecular systems for the controlled delivery of amitriptyline hydrochloride (AMT). The βCD-derived nanosponges provide host–guest cavities for drug inclusion, while the PVA network acts as a diffusion-regulating matrix. Initially, adsorption–desorption studies were performed on isolated CDNSs to evaluate their drug-loading capacity prior to incorporation into the hydrogels. The CDNSs exhibited efficient encapsulation (∼60%) and released more than 90% of the drug, confirming strong yet reversible host–guest interactions within CDs cavities. The drug-loaded CDNSs were subsequently dispersed in PVA solutions and physically cross-linked by freeze–thaw cycling, producing hydrogels containing embedded supramolecular reservoirs. Increasing the PVA concentration (from 14 to 20% w/v) generated denser polymer networks, reducing the swelling degree from ∼60 to ∼30 and slowing water uptake. CDNSs incorporation altered the hydrogel microstructure and introduced additional drug–matrix interactions, resulting in reduced burst release, measurable lag times, and more prolonged release compared with neat PVA hydrogels. Release kinetics were best described by the Weibull model, indicating diffusion-controlled transport in the pure matrices and heterogeneous diffusion behavior in the hybrid systems. Overall, AMT release is governed by coupled mechanisms involving diffusion through the polymer network and dissociation from cyclodextrin host sites, with CDNSs acting as supramolecular reservoirs within the hydrogel matrix.