Functional Polyselenoureas for Selective Gold Recovery Prepared from Catalyst-Free Multicomponent Polymerizations of Elemental Selenium

Abstract

Selenium-containing polymers with fascinating functionalities such as stimuli-responsive property, enzyme mimics, antioxidant activity, promotion of immune-cell activity, anticancer activity, and controlled delivery property, are highly desired, but rarely developed due to their underexplored synthetic methods. Herein, through careful design of monomeric structures and polymerization conditions, we report a series of catalyst-free multicomponent polymerizations (MCPs) of elemental selenium with aliphatic/aromatic diamines and diisocyanides that directly converted selenium to polyselenoureas with long-term stability, good solubility, well-characterized structures, and unique functionalities. The MCPs enjoyed broad monomer scope and fast conversion in 1 min, delivering 18 polyselenoureas with high molecular weights (M w s up to 94,600 g/mol) in high yields (up to 99%). Furthermore, the polyselenoureas could be used for the extraction of Au 3+ from mixed-metal ion solutions under practical conditions with high selectivity, sensitivity (< 1 μg/L), efficiency (> 99.99%), and capacity (up to 665.60 mg•Au 3+ /g) within 1 min. Further, the elemental gold was recoverable after the pyrolysis of the polymer complexes.

Precisely Alternating Copolymerization of Episulfides and Isothiocyanates: A Practical Route to Construct Sulfur-Rich Polymers

“…However, current routes to construct sulfur-rich polymers, especially well-defined ones still remain rare due to the limitations on the easily available sulfur-containing feedstocks. Elemental sulfur is a promising sulfur source, and its multicomponent copolymerization has been extensively studied to deliver polythioureas or polythioamides. − While this strategy is facile and effective, the insolubility of the elemental sulfur usually leads to unsatisfied reactivity and broad polydispersity index ( Đ ) . Uncontrolled polymerization behavior also tortures other dithiols and thiolactones involved synthetic strategies. − In contrast, ring-opening polymerization (ROP) and ring-opening copolymerization (ROCOP) are promising alternatives to target well-defined polymers in a controlled manner. − A variety of sulfur-containing monomers have been demonstrated to be able to give well-defined polymers in mild conditions, as exemplified by poly­(thioester)­s through ROCOP of cyclic thioanhydrides and episulfides. ,, Besides, ROCOP of heteroallene comonomers (CS 2 , COS) with epoxides and episulfides offers an atom-economical approach to sulfur-containing macromolecules, − however, tailor-made catalysts and monomer combinations are generally required to mitigate the involved oxygen–sulfur exchange side reactions. − …”

Facile Multicomponent Polymerizations toward Multifunctional Heterochain Polymers with α,β-Unsaturated Amidines

“…To meet the high annual demand for gold, a large part of gold is recycled from gold-containing industrial wastes such as waste circuit boards. , Conventional methods for gold extraction usually suffered from the toxicity of inorganic cyanide and hypochlorite, extreme pH conditions, limited efficiency, and environmental problems. In the recent few years, some green strategies have been developed for effective gold enrichment, such as based on the strong coordination of Au 3+ with sulfur or selenium in hydrophobic polymers, , or complexation with nitrogen atoms especially those involved in metal–organic framework materials, as well as the bacteria-enrichment method . Encouraged by the highly selective and sensitive detection of Au 3+ by P 1e / 2a / 3 , we envisioned that this nitrogen-rich polymer might also be useful for gold enrichment.…”

One-Pot Multicomponent Polymerization, Metal-, and Non-Metal-Catalyzed Synthesis of Organoselenium Compounds

“…In 2019, Wu et al reported the synthesis of functionalized and structurally diverse polyselenoureas via catalyst-free and solvent-free MC polymerizations of elemental Se, diisocyanides, and aliphatic/aromatic diamines. It is worth noting that the obtained polyselenoureas encompassed enhanced thermal stability and solubility, long-term stability, and the potential extraction of gold ions (Au 3+ ) from mixed-metal ion solutions ( Scheme 43 ) [ 91 ].…”