Emerging catalytic systems for hydrogen production via solar and mechanical energy conversion often face critical challenges, including band mismatch, interfacial charge recombination, and insufficient charge migration driving forces. To address core issues of low carrier separation efficiency and poor multi-field coupling in molecular ferroelectrics, this study proposes a molecular engineering strategy of dual molecular ferroelectric heterojunctions. We report a facile one-pot solution synthesis of a molecular ferroelectric heterojunction composed of 4,4-difluoropiperidinium lead iodide and 4,4-difluorocyclohexylamine lead iodide ((4,4-DFPD)₂PbI₄/(4,4-DFCHA)₂PbI₄), tailored for hydrogen iodide (HI) decomposition under simultaneous light -ultrasonic activation. Under dual-field excitation, the heterojunction achieves a remarkable hydrogen evolution rate of 5.26 mmol g⁻¹ h⁻¹, outperforming its individual constituents ((4,4-DFPD)₂PbI₄ and (4,4-DFCHA)₂PbI₄) by factors of 4.5 and 2.4, respectively. Kelvin probe force microscopy (KPFM) confirms efficient charge separation at the heterointerface, facilitated by energy-level alignment and polarization coupling. Both experimental and theoretical investigations attribute the enhanced performance to suppressed charge recombination and the synergistic action of ferroelectric and piezoelectric fields, jointly promoting directional charge migration. This work not only introduces a viable molecular ferroelectric strategy for designing high-efficiency piezo-photocatalytic systems but underscores the critical role of interfacial charge dynamics in catalytic optimization, offering theoretical insights and practical guidelines for next-generation solar-driven catalysts.