Spatiotemporal Regulation in Porous Organic Cage Salt-Metal Cluster Hybrids for Efficient Orthogonal Tandem Catalysis.

Developing artificial biomimetic catalysts with precise spatiotemporal control remains challenging. Here, we present a pH-responsive organic cage salt containing quaternary ammonium moieties ([QA-Cage]-12X, X═Cl or Br counteranions) as a platform for constructing such catalysts. Thermally induced electron transfer from counteranions to ammonium moieties generates radicals throughout cage skeletons ([QA-Cage]-12X), which, combined with nanocavity confinement, facilitates metal precursor reduction and Pd cluster encapsulation, yielding the hybrid catalyst, Pd@[QA-Cage]-12X. The pH-responsive cages enable switching between two catalytic states: Pd@[QA-Cage]-12X, where radicals serve as active sites while Pd accessibility is hindered by numerous counteranions, and Pd@A-Cage, where neutralization of ammonium cages to non-radical amine cages (A-Cage) restores Pd accessibility by removing counteranions and modulating Pd surface charge. This dynamic switching allows real-time modulation of site-specific activity in single-step reactions. Sequential activation of dual active sites by acid-base stimuli enables tandem catalysis. Moreover, fine-tuning the protonation degrees of quaternary ammonium groups with base stimuli unveils an optimized catalyst, Pd@[PQA-Cage]-6X (where PQA-Cage refers to partially quaternized ammonium cages). Such a spatiotemporal control maximizes cooperative performance by balancing spatially isolated radicals and Pd sites for efficient orthogonal tandem catalysis of incompatible oxidation and reduction reactions in one pot.