Porous organic polycarbene nanotrap for efficient and selective gold stripping from electronic waste

Abstract

The role of N-heterocyclic carbene, a well-known reactive site, in chemical catalysis has long been studied. However, its unique binding and electron-donating properties have barely been explored in other research areas, such as metal capture. Herein, we report the design and preparation of a poly(ionic liquid)-derived porous organic polycarbene adsorbent with superior gold-capturing capability. With carbene sites in the porous network as the “nanotrap”, it exhibits an ultrahigh gold recovery capacity of 2.09 g/g. In-depth exploration of a complex metal ion environment in an electronic waste-extraction solution indicates that the polycarbene adsorbent possesses a significant gold recovery efficiency of 99.8%. X-ray photoelectron spectroscopy along with nuclear magnetic resonance spectroscopy reveals that the high performance of the polycarbene adsorbent results from the formation of robust metal-carbene bonds plus the ability to reduce nearby gold ions into nanoparticles. Density functional theory calculations indicate that energetically favourable multinuclear Au binding enhances adsorption as clusters. Life cycle assessment and cost analysis indicate that the synthesis of polycarbene adsorbents has potential for application in industrial-scale productions. These results reveal the potential to apply carbene chemistry to materials science and highlight porous organic polycarbene as a promising new material for precious metal recovery.

Selective and Light-Enhanced Au(III) Recovery by a Porphyrin-Based Metal–Organic Framework: Performance and Underlying Mechanisms

“…The higher ζ-potential of PCN-224 in light led to relatively stronger repulsion to positive nonprecious metal ions, thus showing enhanced selectivity. In summary, we found that visible light largely promoted the Au recovery performance of PCN-224 and made it superior to other materials in terms of recovery capacity ( q max ) and selectivity ( K d ), including UiO-66, COFs, − polymers, ,,, and 2D materials ,, (Figure S9).…”

“…We also noted that visible light enhanced the selectivity of Au by both increasing the recovery of Au(III) and decreasing the uptake of nonprecious metals. Under light irradiation, the uptake of Zn and made it superior to other materials in terms of recovery capacity (q max ) and selectivity (K d ), including UiO-66, 57 COFs, 58−61 polymers, 37,38,62,63 and 2D materials 33,64,65 (Figure S9).…”

Rapid and Selective Gold Stripping from Electronic Waste with Yolk–Shell-Structured Ion-Imprinted Magnetic Mesoporous Nanorobots for Efficient Water Decontamination

“…It can be seen from the high-resolution spectra of Au 4f (Figure c) that the peaks at 87.62 and 83.91 eV correspond to the Au 4f 5/2 and Au 4f 7/2 of Au­(III), indicating that the adsorption process occurred only by chelation without redox reaction, which was the reason why the adsorption amount of MMNR-IIP-YS was not high . In addition, the spectrum of N 1s can be divided into two characteristic peaks at 402.05 and 399.80 eV attributed to CN and C–N, respectively (Figure d). Noteworthily, both CN and C–N groups moved to higher binding energy after binding with Au­(III), and the characteristic binding energies of O 1s and C 1s hardly changed (Figure S9), indicating that there was strong chelation between the nitrogen-containing group and Au­(III).…”

“…Among them, adsorption has been recognized as a feasible and environmentally friendly strategy due to its easy operation, low cost, high efficiency, and green process . Recently, numerous novel gold adsorbents with high capacities have already been explored, such as metal–organic frameworks (MOFs), − porous organic polymers (such as covalent organic frameworks, porous aromatic frameworks, , porous organic polycarbene, and porous porphyrin polymer , ), functionalized silicas, polysaccharides, chelating resins, and modified fibers . Although these adsorbents were effective in capturing gold from electronic waste, their tedious synthetic procedures, high-cost precursors, poor selectivity, and slow kinetics of some of them impede their practical applications.…”

Chemically Controlled Reversible Magnetic Phase Transition in Two-Dimensional Organometallic Lattices

“…It should be noted that the experimental synthesis of these 2D organometallic frameworks would be challenging because the N and O atoms of the ligands may compete with C atoms and coordinate to Cr. To solve this issue, one possible route is via forming metal–carbene bonds between transition metals and ligands. , Another possible route is to employ organic ligands with additional heteroatoms that can stably coordinate with transition metals. A potential example is the 5,5′-dihydroxyl-substituted 4,4′-bipyrimidine, where the opposite N atoms in 1,1′ position are used to bind transition metals, and the other two N atoms in the 3,3′ position are involved in tautomerization.…”