Thiol grafted imine-based covalent organic frameworks for water remediation through selective removal of Hg(ii)

Abstract

An outstanding and selective material for Hg(ii) polluted water remediation based on an imine-linked COF endowed with triazole and thiol groups.

Gas–Solid Heterogeneous Postsynthetic Modification of Imine‐Based Covalent Organic Frameworks

“…As the starting materials for the reaction we selected [HC≡C] 0.5 ‐TPB‐DMTP‐COF and two azides previously unreported in the postsynthetic modification of COFs: benzyl azide and ( S )‐2‐(azidomethyl)‐1‐Boc‐pyrrolidine (Scheme ). [HC≡C] 0.5 ‐TPB‐DMTP‐COF has been extensively used in the literature as a platform for postsynthetic modification due to its high crystallinity, porosity and chemical stability . Before the cycloaddition reaction, the material was characterized by Fourier transform infrared spectroscopy (FTIR), 13 C cross‐polarized magic‐angle‐spinning solid‐state NMR ( 13 C CP‐MAS‐NMR), powder X‐ray diffraction (PXRD) and nitrogen adsorption–desorption measurements at 77 K. All the data are in accordance with those already reported (Figure and Figure S3 in the Supporting Information).…”

Tailoring Covalent Organic Frameworks To Capture Water Contaminants

“…The azide-alkyne cycloaddition reaction is, to date, the most commonly used method for pore surface functionalization of COFs. Such reactions are attractive for PSM due to their high yields, large substrate scope, and simplicity of the procedures.B oth azide [116,117] and alkyne [49,[118][119][120][121][122][123] substituents have been incorporated into COFs ands uccessfullyc onverted further to give functionalized pore surfaces. However,ahigh degree of functionalization of the pore walls is usually associated with ar eductioni nt he porosity,a nd sometimes even crystallinity,o f the COF material, and for an optimal material ab alance needs to be found between sufficient porosity and amount of functionalities.…”

“…The frameworks explored for this applicationh ave typicallyf eatured either tetragonal or hexagonal pores (Scheme 1). Promising results have been obtained for the captureo f, for example, organic dyes, [31][32][33][34][35] perfluoroalkyl substances, [36] aryl-organophosphorous flame retardants, [37] pesticides, [38][39][40] phenol endocrine disruptors, [41,42] lactic acid, [43] iodine, [44,45] mercury, [46][47][48][49] radionuclides, [50] lanthanides, [51] and oil spills. [52] We found COFs to efficiently adsorb biotoxins from seawater [53] andp harmaceuticalc ontaminants from water, [54] expanding their use to these classes of hazardouscompounds.…”

Amidation, Esterification, and Thioesterification of a Carboxyl‐Functionalized Covalent Organic Framework

“…Theperformance of this series of functionalized COFs (COF-616, COF-616-NS4',COF-616-CY,COF-616-IMD,COF-616-MTE, and COF-616-DTT) as well as the unfunctionalized COF-4PE-3P [23,24] were assayed for the uptake of metal ions (K + ,C a 2+ ,P b 2+ ,H g 2+ ,C u 2+ ,Z n 2+ ,a nd Ni 2+ )f rom water (Figure 4a). While the thiol groups of COF-616-DTT outperformed other chelators due to their superior soft Lewis basicity, [18,25,26] nitrogen-rich chelators also showed appreciable adsorption of heavy metal ions (i.e., COF-616-CY for removal of Pb 2+ ,Cu 2+ ,Zn 2+ ,and Ni 2+ ,and COF-616-IMD for removal of Hg 2+ ), thus providing av iable alternative for designing heavy metal ions adsorbents.T he varying uptake capacities and selectivities towards heavy metal ions with different chelating groups ( Figure S32) illustrate the impor-tance of screening and optimizing the performance of agiven framework by appending al ibrary of functional groups through facile post-synthetic modification.…”

“…Postsynthetic modification provides higher versatility,w ith click chemistry currently being the most widely-used protocol. [17,18] However,c onducting such copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions on COFs generally requires anaerobic handling, involves heterogeneous Cu I catalysts that need to be removed from the pores of the framework, and is incompatible with molecules featuring chelating functionalities-all of which greatly limit the generality of this approach. As such, am ore general and facile strategy for post-synthetic modification of COFs is highly sought after.…”