Piezocatalysis and piezo-photocatalysis of metal-organic frameworks: from symmetry- and mechanism-based classification, design to applications

Faced with escalating energy shortages and environmental pollution, it is crucial to develop eco-friendly catalytic technologies capable of harnessing ambient mechanical energy and/or solar energy. Metal-organic frameworks (MOFs) have shown great promise in piezocatalysis and piezo-photocatalysis due to their high structural tunability, abundant surface sites, well-defined porous architectures, and adjustable electronic structure. However, further advancement of MOFs in this field remains constrained by ambiguous intrinsic piezoelectric origins, poorly resolved structure-activity relationships, and insufficient catalytic stability. Moreover, despite growing interest, a systematic classification framework linking MOF structural features to piezoelectric response mechanisms is still absent. To fill this gap, we first introduce the fundamental principles of MOF-based piezocatalysis and piezo-photocatalysis, with a discussion of their structural advantages as piezoelectrics. Then, we propose a multi-level classification system based on crystal symmetry, piezoelectric response mechanisms, and functional dimensionality, which allows to directly target the root structural determinants of piezoelectricity in MOFs. Subsequent sections summarize current MOF modification strategies, including molecular-scale engineering, morphology control, and interfacial engineering. Finally, the current application status of MOFs in environmental remediation, energy carrier production, and biomedicine are presented. The key challenges facing practical implementation are discussed, and targeted forward-looking are proposed. This review aims to provide constructive guidance for the rational design and practical application of MOF-based piezocatalytic and piezo-photocatalytic materials.