Synthesis and Engineering of Bio-Based Porous Organic Polymers for Gold Recovery

The development of functional porous materials from renewable resources offers a promising strategy to reduce reliance on fossil-derived feedstocks and advance sustainable materials technologies. Here, we report the facile synthesis of bio-based porous organic polymers (bioPOPs) through the polycondensation of vanillin-derived organic dialdehydes and inexpensive diamine monomers. The synthetic approach demonstrates good generality, enabling vanillin-derived monomers bearing different functional substituents (H, OH, CH3, OCH3, and NO2) to be converted into bioPOPs with high specific surface areas of up to 523 m2/g and abundant microporosity. Furthermore, cellulose nanofibers (CNF) were employed as templates for the in situ interfacial polymerization of bioPOPs on their surfaces, allowing the resulting hybrid nanofibers to be processed into freestanding composite films. Benefiting from their rich microporosity and abundant nitrogen-containing functional groups, both pristine bioPOPs and CNF@bioPOP composite films exhibited efficient [AuCl4]- capture from aqueous solutions, with adsorption capacities of up to 1093 mg/g, rapid adsorption kinetics, and excellent selectivity over competing metal ions. More importantly, the materials demonstrated highly efficient and selective gold recovery from real electronic waste leachate, highlighting their potential for preciousmetal recovery from secondary resources. The freestanding composite films further offer advantages for practical separation applications through their processability and potential integration into continuous flow systems. Overall, this work demonstrates the transformation of renewable resources into functional porous materials for precious-metal recovery from secondary waste streams, establishing a fully sustainable and circular approach to resource utilization.