Lingbin Lu

Developing sustainable and molecularly selective adsorbents for heavy-metal removal remains a critical challenge in water purification. Herein, we report a green molecular-engineering approach for fabricating aza-crown ether functionalized sodium alginate aerogels (ACSA) capable of highly selective Cu²⁺ capture. The aerogels were synthesized via saccharide-ring oxidation, Cu²⁺-templated self-assembly, and reductive amination, enabling the covalent integration of aza-crown ether motifs within a hierarchically porous biopolymer matrix. Structural analyses (FTIR, ¹³C NMR, XPS, SEM, TGA) confirmed the in situ formation of macrocyclic N/O coordination sites. Owing to their interconnected porosity and chemically stable framework, ACSA exhibited rapid sorption kinetics following a pseudo-second-order model (R² = 0.999) and a Langmuir maximum adsorption capacity of 150.82 mg·g⁻¹. The material displayed remarkable Cu²⁺ selectivity over Zn²⁺, Cd²⁺, and Ni²⁺, arising from the precise alignment between Cu²⁺ ionic radius (0.73 Å) and crown-cavity dimensions, synergistic N/O chelation, and Jahn-Teller stabilization. Over four regeneration cycles, ACSA retained more than 80% of its original adsorption capacity, confirming excellent durability and reusability. This saccharide-ring modification strategy eliminates crown-ether leaching and weak anchoring, offering a scalable and environmentally benign route to bio-based adsorbents that combine molecular recognition with structural stability for efficient Cu²⁺ remediation and beyond.

The frequent occurrence of crude oil spills and the indiscriminate discharge of oily wastewater have caused serious environmental pollution. The existing separation methods have some defects and are not suitable for complex oil–water emulsions. Therefore, the efficient separation of complex oil–water emulsions has been of great interest to researchers. Asymmetric wettable Janus materials, which can efficiently separate complex oil–water emulsions, have attracted widespread attention. This comprehensive review systematically summarizes the research progress of asymmetric wettable Janus materials for oil–water separation in the last decade, and introduces, in detail, the preparation methods of them. Specifically, the latest research results of two-dimensional Janus materials, three-dimensional Janus materials, smart responsive Janus materials, and environmentally friendly Janus materials for oil–water separation are elaborated. Finally, ongoing challenges and outlook for the future research of asymmetric wettable Janus materials are presented.