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

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 WO4 2- 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 PW9O34 9- ({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.