The chemistry of multi-component and hierarchical framework compounds
Multi-component hierarchically porous materials are an emerging class of materials with tailored compositions, tunable distribution and sophisticated applications. An increasing demand for multifunctionalities and hierarchical structures has resulted in extensive studies on multi-component hierarchical metal–organic frameworks and other open framework compounds. This review article focuses on recent advances in multi-component and hierarchical framework materials, covering the design and synthetic strategies of these architectures, their characterization, and the latest applications. Multivariate MOFs prepared under various synthetic conditions (one-pot or post-synthetic) and their building block distributions are introduced and summarized. This is followed by a short review of characterization techniques including solid-state NMR and photothermal induced resonance, and their potential applications in gas storage, separation, heterogeneous catalysis, guest delivery, and luminescence. Furthermore, guided by the same design principles, the synthesis and applications of multi-component hierarchical covalent-organic frameworks, metal–organic cages and porous organic cages are introduced and discussed. Together, this review is expected to provide a library of multi-component hierarchically porous compounds, which could also guide the state-of-the-art design and discovery of future porous materials with unprecedented tunability, synergism and precision.