Real-time tracking of molecular cluster assembly and precise hierarchical reassembly into pure POM host–guest architecture

Abstract

In this work, we report an in operando spectroscopy strategy to track the molecular cluster assembly and thereby realize a precise bottom-up hierarchical reassembly of building blocks into a pure POM host–guest architecture. Through precise flow chemical synthesis combined with in operando Raman characterization, we systematically tracked key building block intermediates emerging during the evolution from WO₄²⁻ precursors to the {P₂W₁₈} cluster and validated with ESI-MS and ³¹P NMR. Capitalizing on the dynamic assembly behaviour, we further realized precise hierarchical re-assembly of building blocks PW₉O₃₄⁹⁻ ({PW₉}): eight {PW₉} were used as secondary building units (SBUs) to form tertiary building units (TBUs, K₄₂P₈W₇₂, and {PW₉}₈), and then TBUs were further linked by alkali metals, resulting in a purely inorganic host–guest architecture {[K₆₆Na₁₄H₁₀(H₂O)₁₅₀(PW₉O₃₄)₈]·(PW₉O₃₄)₂·43H₂O} (compound 1, {PW₉}₂@{PW₉}₈) with interpenetrating three-dimensional channels containing discrete nano-sized SBUs. Unlike the irreversible and limited electrochemical reaction behaviour of SBUs, compound 1 exhibited markedly distinct electrochemical properties with multi-step multi-electron redox behaviours at 0.23 V, 0.01 V, −0.49 V and −0.87 V vs. NHE, respectively. These findings refine the understanding of the assembly behaviours and pave the way for designing atomically defined and functional clusters.