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With the fast-growing accumulation of electronic waste and rising demand for rare metals, it is compelling to develop technologies that can promotionally recover targeted metals, like gold, from waste, a process referred to as urban mining. Thus, there is increasing interest in the design of materials to achieve rapid, selective gold capture while maintaining high adsorption capacity, especially in complex aqueous-based matrices. Here, a highly porous metal-organic framework (MOF)–polymer composite, BUT-33–poly( para -phenylenediamine) (PpPD), is assessed for gold extraction from several matrices including river water, seawater, and leaching solutions from CPUs. BUT-33–PpPD exhibits a record-breaking extraction rate, with high Au 3+ removal efficiency (>99%) within seconds (less than 45 s), a competitive capacity (1600 mg/g), high selectivity, long-term stability, and recycling ability. Furthermore, the high porosity and redox adsorption mechanism were shown to be underlying reasons for the material’s excellent performance. Given the accumulation of recovered metallic gold nanoparticles inside, the material was also efficiently applied as a catalyst.

The traditional vacuum activation of covalent organic framework (COF) materials typically erodes the materials' crystallinity significantly and then reduces the surface area of isolated materials. Developing new methods for synthesizing robust COFs which could survive the duration of the vacuum activation process is of great practical significance. In this work, a robust imine-linked 2D COF TAPB-TA was creatively constructed in supercritical CO 2 (ScCO 2 ) with γ-valerolactone (GVL) as a cosolvent instead of previously widely reported reaction conditions. Upon vacuum activation, the as-prepared COF (denoted as Sc-COF) via this green synthesis could still possess a high surface area, while preventing the pores from undesirable collapse and the loss of material quality could be avoided successfully. Further, Sc-COF showed excellent stability toward solvent immersion−reactivation cycles. Furthermore, this method is universal and can be facilely extended to the synthesis of other iminelinked 2D COFs and is expected to be transferable to a broader range of customized COFs. Theoretic calculations imply that ScCO 2 serves to attenuate the COF−COF interactions during the activation process preventing the collapse of the structure. It decreases the viscosity of the solution as compared to pure GVL, enabling fast diffusion kinetics of monomers to the reactive sites. Moreover, thanks to the low dielectric constant, usage of the ScCO 2 solvent diminishes the energy barriers of imine bond formation, thus facilitating ordered COF growth. These insights have important implications for studying and understanding how more robust 2D COFs could form and thus greatly expand their practical applications.

Electrochemical conversion of CO2 into liquid fuels such as ethanol, powered by renewable electricity, is an efficient strategy for CO2 utilization to produce high value-added products. In this work, we...

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