Breaking of π-Continuity by σ-Linkers in Covalent Organic Frameworks for Efficient Photoreduction and Recovery of Gold From Electronic Waste.

Photoreduction of metal ions plays a central role in the recovery of precious metals from electronic waste, yet its design is still largely governed by a semiconductor paradigm that links extended π-conjugation and long-range charge transport to superior performance. Herein, we challenge this assumption by demonstrating that deliberate disruption of π-continuity via σ-linkers in covalent organic frameworks (COFs) affords a more effective electronic architecture for localized redox reactions. The resulting π-disrupted framework (σ-COF) generates low-energy, spatially confined electronic states that prolong photogenerated electron lifetimes and promote their transfer to adsorbed Au(III) species. Under illumination, σ-COF exhibits a dramatic enhancement in gold uptake from electronic-waste-derived solutions, increasing from ∼1000 to 3045 mg/g, whereas a structurally analogous π-conjugated framework (π-COF) shows only a modest increase (from ∼1200 to 1700 mg/g). Spectroscopic and photoelectrochemical studies reveal efficient electron accumulation at redox-active sites without reliance on extended π-delocalization, with adsorption and reduction occurring within the same local domains. This work establishes controlled π-disruption as a new electronic design principle for COF photoreductants in noble metal recovery.