Cooperative Multiscale-Assembly for Directional and Hierarchical Growth of Highly Oriented Porous Organic Cage Single-Crystal Microtubes and Arrays

Abstract

The directional assembly of porous organic molecules into long-range ordered architectures, featuring controlled hierarchical porosity and oriented pore channels with defined spatial arrangements, is a fundamental challenge in chemistry and materials science. Herein, using porous organic cages as starting units, we present a cooperative multiscale-assembly strategy enabling the simultaneous alignment of pore channels and directional hierarchical growth in a single step. At the microscopic level, we employed double solvents to manipulate the intermolecular packing of microporous tetrahedral [4+6] imine cages (CC1 and CC3), resulting in pore channel orientation. Concurrently, at the mesoscopic level, convective flow in the double-solvent system directed the spatial distribution of nuclei species, followed by diffusion limited growth, leading to the directional formation of single-crystal microtubes. By precisely controlling the direction of convective flow, the nanocages were successfully organized into 2D and 3D single-crystal microtube arrays while maintaining oriented micropores. This hierarchical porous architecture enhanced mass transfer, as confirmed by adsorption measurements. Interestingly, such 3D hierarchical microtube arrays can be utilized to immobilize Pd clusters and enzymes (lipase or Glucose oxidase) within the micro- and macropores, respectively, showing a 3.8- to 4-fold enhancement in one-pot tandem reaction activity compared to physical mixtures of individual analogues.