Adaptive Molecular Weaving for Efficient Isotope Separations
Isotope separations, particularly the separation of water isotopologues (H2O, HDO, D2O), are critical yet challenging due to their nearly identical physicochemical properties. Conventional methods such as distillation and electrolysis are energy-intensive and inefficient. Here, we report a molecularly woven porous polymer (PWPN-1) that achieves efficient room-temperature separation of water isotopologues via adaptive framework dynamics. PWPN-1 is constructed from interlaced two-dimensional woven layers linked by B←N coordination nodes, forming a three-dimensional flexible framework. Upon activation, it undergoes reversible contraction along the crystallographic c-axis, exhibiting a breathing behavior that creates differentiated adsorption sites favoring D2O retention. Gas-phase breakthrough experiments demonstrate markedly different retention times for H2O (223 min g−1) and D2O (686 min g−1), with clearly resolved breakthrough curves for H2O/HDO/D2O mixtures under continuous flow. The material is synthesized on a 100-gram scale with ~95% yield and remains stable over multiple adsorption-desorption cycles. Single-crystal structure analyses, combined with path-integral molecular dynamics and DFT calculations, reveal that D2O exhibits slightly stronger binding energies (by 1–2 kJ mol−1) and higher diffusion barriers, arising from nuclear quantum effects. These small energetic differences are amplified by the flexible woven topology, enabling efficient isotope separation under ambient conditions. This work represents a conceptual advance in materials design, transposing macroscopic weaving to the molecular scale for practical isotope enrichment.