Pressure‐Enhanced Antiparallel Stacking Enables Full‐Visible‐Spectrum Piezochromism in MIL‐140B Nanocrystals

ABSTRACT Full‐visible‐spectrum piezochromic materials hold significant potential for applications in pressure sensing, smart displays and anti‐counterfeiting. Polycyclic aromatic hydrocarbons (PAHs) have emerged as promising candidates owing to the inherent π–electron structure. However, the loose and parallel π–π stacking configuration leads to severe quenching of photoluminescence (PL). An effective approach is to construct PAHs into metal–organic frameworks (MOFs) to form an antiparallel π–π stacking arrangement. In this study, we demonstrate that MIL‐140B nanocrystals (NCs) achieve full‐visible‐spectrum piezochromism during compression, with a substantial 212 nm PL bathochromic shift, which exceeds the PL range of all previously reported MOFs. Integrated experimental and computational analyses reveal that the organic linkage, 2,6‐naphthalenedicarboxylic acid (NDC), in MIL‐140B NCs form an antiparallel π–π stacking configuration at ambient conditions, thereby reducing the initial π–π conjugation and boosting the PL efficiency. The enhanced π–π stacking between NDC units under pressure progressively narrows the band gap, which enables full‐visible‐spectrum piezochromism. These findings not only highlight the potential of piezochromic MOFs, but also provide new perspectives for pressure‐sensing under extreme conditions.