Microporous Polyacylhydrazone Membranes with 3D Interconnected Nanochannels for Accurate Molecular Sieving

Abstract

Microporous membranes featuring 3D nanochannels present a compelling avenue for energy-efficient liquid separations, attributable to their tunable interconnected through-pore structures. However, the rational design of 3D-nanochannel membranes that simultaneously achieve high permeance and selectivity remains a challenge, arising from the scarcity of appropriate molecular building blocks and the reliance on empirical synthetic methods. Herein, an innovative 3D polyacylhydrazone (PAH) membrane with unique pore-interconnected structures is constructed on a porous hydrogel using contorted tetrahedral aldehydes (TFS) monomers via an in situ interface-confined strategy. Manipulation of side alkyl chain lengths within terephthalohydrazide (TPH) derivates enabled the enhancement of microporosity and tunable pore environment of PAH nanofilms. Molecular dynamics simulations revealed that TPH_EO linkers with higher reactivity and moderate steric hindrance facilitate superior pore interconnectivity and sharpened pore size distributions. The resulting PAH membranes achieved exceptional methanol permeances of 10.1 L m⁻² h⁻¹ bar⁻¹ and small molecular weight cut-offs of 310 Da, outperforming the state-of-the-art polyamide membranes. This further translated into an outstanding capability in the fractionation of active pharmaceutical ingredients within organic solvent systems. This work demonstrates the efficacy of rational molecular design in developing high-microporosity membranes with tailored interconnected nanochannels, underscoring the potential of 3D microporous membranes for accurate molecular separations.