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Abstract Developing an eco-friendly, efficient, and highly selective gold-recovery technology is urgently needed in order to maintain sustainable environments and improve the utilization of resources. Here we report an additive-induced gold recovery paradigm based on precisely controlling the reciprocal transformation and instantaneous assembly of the second-sphere coordinated adducts formed between β-cyclodextrin and tetrabromoaurate anions. The additives initiate a rapid assembly process by co-occupying the binding cavity of β-cyclodextrin along with the tetrabromoaurate anions, leading to the formation of supramolecular polymers that precipitate from aqueous solutions as cocrystals. The efficiency of gold recovery reaches 99.8% when dibutyl carbitol is deployed as the additive. This cocrystallization is highly selective for square-planar tetrabromoaurate anions. In a laboratory-scale gold-recovery protocol, over 94% of gold in electronic waste was recovered at gold concentrations as low as 9.3 ppm. This simple protocol constitutes a promising paradigm for the sustainable recovery of gold, featuring reduced energy consumption, low cost inputs, and the avoidance of environmental pollution. 

Although catenanes comprising two ring-shaped components can be made in large quantities by templation, the preparation of three-dimensional (3D) catenanes with cage-shaped components is still in its infancy. Here, we report the design and syntheses of two 3D catenanes by a sequence of S N 2 reactions in one pot. The resulting triply mechanically interlocked molecules were fully characterized in both the solution and solid states. Mechanistic studies have revealed that a suit[3]ane, which contains a threefold symmetric cage component as the suit and a tribromide component as the body, is formed at elevated temperatures. This suit[3]ane was identified as the key reactive intermediate for the selective formation of the two 3D catenanes which do not represent thermodynamic minima. We foresee a future in which this particular synthetic strategy guides the rational design and production of mechanically interlocked molecules under kinetic control. 

Transition-metal-catalyzed C–H alkylation reactions directed by aldehydes or ketones have been largely restricted to electronically activated alkenes. Herein, we report a general protocol for the Ir( iii )-catalyzed ortho C–H alkylations of (hetero)aromatic aldehydes using alkyl boron reagents as the coupling partner. Featuring aniline as an inexpensive catalytic ligand, the method was compatible with a wide variety of benzaldehydes, heterocyclic aldehydes, potassium alkyltrifluoroborates as well as a few α,β-unsaturated aldehydes. An X-ray crystal structure of a benzaldehyde ortho C–H iridation intermediate was also successfully obtained. 

Two-photon excited near-infrared fluorescence materials have garnered considerable attention because of their superior optical penetration, higher spatial resolution, and lower optical scattering compared with other optical materials. Herein, a convenient and efficient supramolecular approach is used to synthesize a two-photon excited near-infrared emissive co-crystalline material. A naphthalenediimide-based triangular macrocycle and coronene form selectively two co-crystals. The triangle-shaped co-crystal emits deep-red fluorescence, while the quadrangle-shaped co-crystal displays deep-red and near-infrared emission centered on 668 nm, which represents a 162 nm red-shift compared with its precursors. Benefiting from intermolecular charge transfer interactions, the two co-crystals possess higher calculated two-photon absorption cross-sections than those of their individual constituents. Their two-photon absorption bands reach into the NIR-II region of the electromagnetic spectrum. The quadrangle-shaped co-crystal constitutes a unique material that exhibits two-photon absorption and near-infrared emission simultaneously. This co-crystallization strategy holds considerable promise for the future design and synthesis of more advanced optical materials.

 

The recognition and separation of anions attracts attention from chemists, materials scientists, and engineers. Employing exo‐binding of artificial macrocycles to selectively recognize anions remains a challenge in supramolecular chemistry. We report the instantaneous co‐crystallization and concomitant co‐precipitation between [PtCl₆]²⁻dianions and cucurbit[6]uril, which relies on the selective recognition of these dianions through noncovalent bonding interactions on the outer surface of cucurbit[6]uril. The selective [PtCl₆]²⁻dianion recognition is driven by weak [Pt−Cl⋅⋅⋅H−C] hydrogen bonding and [Pt−Cl⋅⋅⋅C=O] ion–dipole interactions. The synthetic protocol is highly selective. Recognition is not observed in combinations between cucurbit[6]uril and six other Pt‐ and Pd‐ or Rh‐based chloride anions. We also demonstrated that cucurbit[6]uril is able to separate selectively [PtCl₆]²⁻dianions from a mixture of [PtCl₆]²⁻, [PdCl₄]²⁻, and [RhCl₆]³⁻anions. This protocol could be exploited to recover platinum from spent vehicular three‐way catalytic converters and other platinum‐bearing metal waste.

 

The recognition and separation of anions attracts attention from chemists, materials scientists, and engineers. Employing exo‐binding of artificial macrocycles to selectively recognize anions remains a challenge in supramolecular chemistry. We report the instantaneous co‐crystallization and concomitant co‐precipitation between [PtCl₆]²⁻dianions and cucurbit[6]uril, which relies on the selective recognition of these dianions through noncovalent bonding interactions on the outer surface of cucurbit[6]uril. The selective [PtCl₆]²⁻dianion recognition is driven by weak [Pt−Cl⋅⋅⋅H−C] hydrogen bonding and [Pt−Cl⋅⋅⋅C=O] ion–dipole interactions. The synthetic protocol is highly selective. Recognition is not observed in combinations between cucurbit[6]uril and six other Pt‐ and Pd‐ or Rh‐based chloride anions. We also demonstrated that cucurbit[6]uril is able to separate selectively [PtCl₆]²⁻dianions from a mixture of [PtCl₆]²⁻, [PdCl₄]²⁻, and [RhCl₆]³⁻anions. This protocol could be exploited to recover platinum from spent vehicular three‐way catalytic converters and other platinum‐bearing metal waste.