β-Ketoenamine Covalent Organic Frameworks—Effects of Functionalization on Pollutant Adsorption

Abstract

Water pollution due to global economic activity is one of the greatest environmental concerns, and many efforts are currently being made toward developing materials capable of selectively and efficiently removing pollutants and contaminants. A series of β-ketoenamine covalent organic frameworks (COFs) have been synthesized, by reacting 1,3,5-triformylphloroglucinol (TFP) with different C2-functionalized and nonfunctionalized diamines, in order to evaluate the influence of wall functionalization and pore size on the adsorption capacity toward dye and heavy metal pollutants. The obtained COFs were characterized by different techniques. The adsorption of methylene blue (MB), which was used as a model for the adsorption of pharmaceuticals and dyes, was initially evaluated. Adsorption studies showed that –NO2 and –SO3H functional groups were favorable for MB adsorption, with TpBd(SO3H)2-COF [100%], prepared between TFP and 4,4′-diamine- [1,1′-biphenyl]-2,2′-disulfonic acid, achieving the highest adsorption capacity (166 ± 13 mg g–1). The adsorption of anionic pollutants was less effective and decreased, in general, with the increase in –SO3H and –NO2 group content. The effect of ionic interactions on the COF performance was further assessed by carrying out adsorption experiments involving metal ions. Isotherms showed that nonfunctionalized and functionalized COFs were better described by the Langmuir and Freundlich sorption models, respectively, confirming the influence of functionalization on surface heterogeneity. Sorption kinetics experiments were better adjusted according to a second-order rate equation, confirming the existence of surface chemical interactions in the adsorption process. These results confirm the influence of selective COF functionalization on adsorption processes and the role of functional groups on the adsorption selectivity, thus clearly demonstrating the potential of this new class of materials in the efficient and selective capture and removal of pollutants in aqueous solutions.

Chirality-Controlled Mercapto-β-cyclodextrin Covalent Organic Frameworks for Selective Adsorption and Chromatographic Enantioseparation

“…To illustrate the chiral adsorption capacity of SH-β-CD COFs, tryptophan (Trp) was used as a template molecule in the adsorption experiments. The Langmuir isotherm model is premised on the assumption that the adsorption sites on the adsorbent surface are homogeneous, and consequently, the subsequent experimental data were fitted with this model. − TAPB-DVA COF and [SH-β-CD] x -TAPB-DVA COFs were analyzed under the above conditions to observe the chiral selective adsorption discrepancy between them . Simultaneously, a binary polymer SH-β-CD-DVA-TAPB was prepared by condensation of the monomers TAPB and SH-β-CD-DVA, and the necessity of a stable and ordered crystal structure was indicated by comparing the selectivity of this polymer with that of SH-β-CD COFs.…”

Green and Fast Strategies for Energy‐Efficient Preparation of the Covalent Organic Framework TpPa‐1

“…Additionally, TpPa‐1 obtained by microwave radiation in an organic solvent media gave rise to excellent properties at the same time that with the conventional solvothermal route [25] . Other Tp‐based COFs with longer amines have been synthesized under microwave radiation in organic solvents [26] . The use of water as the solvent in microwave synthesis is rarer, [27,28] and there has not been any report of it in COF TpPa‐1.…”

“…[25] Other Tp-based COFs with longer amines have been synthesized under microwave radiation in organic solvents. [26] The use of water as the solvent in microwave synthesis is rarer, [27,28] and there has not been any report of it in COF TpPa-1.…”

Triazene-Linked Porous Organic Polymers for Heterogeneous Catalysis and Pollutant Adsorption

“…Porous organic polymers (POPs) are an emerging class of reticulated organic macromolecules that combine rigid, covalent structures and intrinsic, permanent porosity with low density, high specific surface area, and thermal and chemical stabilities. − POPs encompass several different families of polymerssuch as porous aromatic frameworks (PAFs), covalent organic frameworks (COFs), covalent triazine frameworks (CTFs), conjugated microporous polymers (CMPs), hyper-cross-linked polymers (HCPs), or polymers with intrinsic microporosity (PIMs), among otherswith differing physical and chemical characteristics, depending on the type of building blocks used and reaction conditions employed. ,− Precisely due to their high synthetic diversity and pore customizability, POPs are regarded as highly potential materials for a wide array of applications in different scientific fields, thus constituting one of the most currently researched topics in materials chemistry. Over the years, POP materials have been successfully used in the most varied applications, such as molecular biosensing, drug delivery systems and related biomedical applications, − gas capture and storage, , optoelectronics and energy storage, − adsorption of pollutants from aqueous solution, − and heterogeneous catalysisincluding conventional, − electrocatalytic, and photocatalytic , variantsamong others.…”