Abstract
Covalent organic frameworks with tunable optical bandgaps and notable piezoelectricity enable sustainable piezo-photocatalytic production of H(2) and H(2)O(2) via pure water splitting. Strong dipole moments can significantly boost piezoelectric properties, necessitating a systematic exploration of their structure-property relationships. Here, we synthesize a series of β-ketoenamine/imine-linked covalent organic frameworks, such as TP-BT-0F/1F/2F-COF, BTA-BT-0F-COF, and TP-SB-COF, through molecular design engineering. The combination of symmetry-breaking benzothiadiazole units and in-plane polarized β-ketoenamine linkages creates a robust dipole moment in TP-BT-0F-COF. This material demonstrates a high piezoelectric coefficient and bandgap narrowing, achieving H(2) and H(2)O(2) production rates of 1501.4 and 1435.8 μmol g(-1) h(-1) under co-exposure to ultrasound (60 W, 40 kHz) and visible light. Density functional theory identifies N(8) and C(6) sites on benzothiadiazole units as potential catalytic sites for H(2) and H(2)O(2) evolution, respectively. Molecular design of covalent organic frameworks with prominent dipole moments advances mechano-optical energy conversion technologies.