Hierarchical assembly of a Ti₂₄ metal-organic polyhedron via kinetic trapping of intermediates.

Abstract

The synthesis of high-nuclearity titanium metal-organic polyhedra (Ti-MOPs) has remained a formidable challenge due to the high oxophilicity and hydrolysis susceptibility of Ti⁴⁺ ions. Herein, we report a Ti₂₄ MOP with a truncated octahedron (tro) topology, which represents the highest nuclearity Ti-MOP reported to date. Beyond structural characterization, we introduce a pathway intervention strategy using Ni²⁺ as a kinetic modulator to trap and structurally characterize two key intermediates-a Ti₁₂ macrocycle and a Ti₁₂ (6-4-6) module. These intermediates outline a hierarchical assembly pathway from simple precursors to Ti₂₄ MOP. Furthermore, we demonstrate that this process is governed by a coordination lability gradient between Ti⁴⁺ and Ni²⁺, providing an effective strategy for directing supramolecular complexity. This Ti-MOP exhibits permanent microporosity, gas separation, and post-assembly modification capability. This work transforms a synthetic challenge into a strategic advantage, offering a blueprint for the rational assembly of complex metal-organic architectures.