Self-Assembly Construction of Biomass Aerogel with Tip-To-Based Gradient Porous Structure to Break Trade-Off Effect for Efficient Water/Oil Separation

Abstract

Self-driven water/oil separation is an effective and sustainable strategy for oil dehydration, and regulating the pore structure of separation materials to break the trade-off effect between flux and retention remains a challenge. Inspired by the tip-to-base conduit widening structure of vascular bundle, an enthalpy‒entropy co-driven strategy based on tannin/amylose non-covalent self-assembly and borate ester dynamic crosslinking is innovatively proposed for constructing a gradient porous biomass aerogel (termed as Si@TAP-B), realizing synchronous improvement of separation flux and retention rate. The permeation fluxes of water/oil mixture and water-in-oil emulsion by Si@TAP-B achieve 17914.7 and 10285.6 L m⁻² h⁻¹, respectively, and the retention rates remain above 99%. The asymmetric solvent transport induced by gradient porous structure optimizes the hydraulic resistance and breaks the trade-off effect of separation flux and retention. Therefore, the emulsion separation flux under forward osmosis (from large pores to small pores) is twice that under reverse osmosis. Additionally, similar to the self-healing ability of plants, Si@TAP-B can restore the original structure and function after severe damage through reversible crosslinking of borate ester bonds and the flow of low surface energy materials. Overall, this novel strategy is desirable for developing biodegradable, efficient, and durable separation materials with unique structures and functions.