Molecular ferroelectrics, known for their lightweight, mechanical flexibility, low cost, and environmental friendliness, are gaining attention as viable alternatives to inorganic ceramics and polymer ferroelectrics. This study proposes a hydrogen bond modification method by introducing hydroxyl groups to enhance the phase transition temperature (Tc) of molecular ferroelectrics. The method successfully boosts the Tc of 1-hydroxy-3-adamantanammonium tetrafluoroborate [(HaaOH)BF4] by at least 336 K, maintaining ferroelectricity up to 528 K. The stable ferroelectric domains can be directly written on the film of (HaaOH)BF4, which can light up 9 blue LEDs and perform self-powered sensing. The hydrogen bond modification strategy is effective in designing molecular ferroelectrics with high Tc and stable ferroelectric domains, offering a promising route for optimizing the performance of molecular ferroelectrics.Molecular ferroelectrics, known for their lightweight, mechanical flexibility, low cost, and environmental friendliness, are gaining attention as viable alternatives to inorganic ceramics and polymer ferroelectrics. This study proposes a hydrogen bond modification method by introducing hydroxyl groups to enhance the phase transition temperature (Tc) of molecular ferroelectrics. The method successfully boosts the Tc of 1-hydroxy-3-adamantanammonium tetrafluoroborate [(HaaOH)BF4] by at least 336 K, maintaining ferroelectricity up to 528 K. The stable ferroelectric domains can be directly written on the film of (HaaOH)BF4, which can light up 9 blue LEDs and perform self-powered sensing. The hydrogen bond modification strategy is effective in designing molecular ferroelectrics with high Tc and stable ferroelectric domains, offering a promising route for optimizing the performance of molecular ferroelectrics.