voltage power sources, and energy harvesting systems. [1][2][3][4][5][6][7] The commercially available piezoelectrics are dominated by conventional ceramics (i.e., lead zirconate titanate, PZT) and polymers (i.e., polyvinylidene difluoride, PVDF). For the former, they often require harsh synthetic conditions and contain toxic heavy metals; while for the later, their piezoelectric performance still needs further improvement. In this regard, developing new kind of piezoelectric materials to overcome these drawbacks is highly thought after. Recently, hybrid organicinorganic piezoelectric materials have attracted extensive attention due to their great structural tunability, mild synthesis conditions, mechanical flexibility, low dielectric constants, and attractive piezoelectric performance. [8][9][10] For instance, an extremely high d 33 of about 1540 pC N −1 was realized in a molecular perovskite solid solution (TMFM) x (TMCM) 1− x -CdCl 3 (TMFM = trimethylfluoromethyl ammonium, TMCM = trimethylchloromethyl ammonium). [11] A following study shows that a 2D perovskite (ATHP) 2 PbBr 4 [12] (ATHP, 4-aminotetrahydropyran) can exhibit a g 33 as large as 660.3 × 10 −3 V m N −1 . These values are even much higher than those of many commercial piezoelectric materials, such as PZT-5H [13] (d 33 = 593 pC N −1 ) and PVDF (g 33 = 286.7 × 10 −3 V m N −1 ). Many of these hybrid piezoelectric materials, however, have the perovskite-type structures which mean that their organic amines (A-site), metal cations (B-site), and halides (X-sites) are limited by the tolerance factors. On the other hand, these hybrid compounds often contain lead or other toxic metals, [10] which inevitably restricting their future applications in eco-friendly environments. Hence, it is of great significance to explore lead-free molecular piezoelectric systems. Some important progresses have been recently made in synthesizing hybrid lead-free organic-inorganic perovskites, and typical examples are TMCM-MnCl 3 (d 33 = 185 pC N −1 , Mn = Manganese), [14] (RM3HQ) 2 RbLa(NO 3 )