Porous Covalent Organic Framework Based Hydrogen‐Bond Nanotrap for the Precise Recognition and Separation of Gold

Abstract

Utilizing weak interactions to effectively recover and separate precious metals in solution is of great importance but the practice remains a challenge. Herein, we report a novel strategy to achieve precise recognition and separation of gold by regulating the hydrogen-bond (H-bond) nanotrap within the pore of covalent organic frameworks (COFs). It is found that both COF-HNU25 and COF-HNU26 can efficiently capture Au III with fast kinetics, high selectivity, and uptake capacity. In particular, the COF-HNU25 with the high density of H-bond nanotraps exhibits an excellent gold uptake capacity of 1725 mg g À 1 , which is significantly higher than that (219 mg g À 1 ) of its isostructural COF (COF-42) without H-bond nanostrap in the pores. Importantly, the uptake capacity is strongly correlated to the number of H-bonds between phenolic OH in the COF and [AuCl 4 ] À in water, and multiple H-bond interactions are the key driving force for the excellent gold recovery and reusability of the adsorbent.

Designing Local Electron Delocalization in 2D Covalent Organic Frameworks for Enhanced Sunlight-Driven Photocatalytic Activity

“…The peak of N 1s at around 400.3 eV was assigned to the C−N bonds of the β-ketoamine linkages. 37 Field emission scanning electron microscopy (FE-SEM) confirmed the homogeneous rod-like crystallites of TPBD-R-COF with nanometer to micrometer sizes (Figures S6−S9 The porosities of all of the materials were determined by N 2 adsorption−desorption isotherms at 77 K. The type IV sorption isotherm plots revealed that each COF exhibited the mesoporous characteristics (Figure 2E). The Brunauer− Emmett−Teller specific surface areas of TPBD-H-COF, TPBD-F-COF, TPBD-CN-COF, and TPBD-NO 2 -COF were calculated to be 1005, 1492, 1073, and 335 m 2 /g, respectively.…”

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).…”

Modulating Skeletons of Covalent Organic Framework for High‐Efficiency Gold Recovery

“…[9] Specifically, several COFs with different functional groups were proposed to endow COFs with specific recognition and high uptakes for gold ions via H-bond interaction. [10] Most COFs for Au capture focused on modifying the porous walls with specified groups (e.g., thiol, phenolic and amide groups) to construct H-bond traps to capture Au. [11] However, the development of frameworks was ignored because of the weak binding ability of the Au ions.…”

“…Introducing binding groups along the pore walls of COFs has been shown to capture various ions such as Hg 2+ , UO 2 2+ , and Cr 4+ [9] . Specifically, several COFs with different functional groups were proposed to endow COFs with specific recognition and high uptakes for gold ions via H‐bond interaction [10] . Most COFs for Au capture focused on modifying the porous walls with specified groups (e.g., thiol, phenolic and amide groups) to construct H‐bond traps to capture Au [11] .…”