Primitive reaction synergy is an effective strategy to construct complex assemblies, but the exploration is still in its infancy. Here, we report an organic–inorganic co-assembly method involving controlled dehydration condensation between boric acid and pyrazole which enables the precise synthesis of five titanium-oxo clusters (TOCs) with two distinct titanium-oxo cores. The parallelepiped Ti₈O₈ core which constructed from the mono-dehydration product (H₂R¹Bpz₂O) with multiple μ₃-O bridges exhibited enhanced structural stability and induced conformational distortion for open metal site exposure. Crucially, the tetrahedral Ti₄O₆ core which was capped with C_3v-symmetric pyrazolylborate ligands (HR²Bpz₃) via the first-reported in situ bis-dehydration exhibited unprecedented acid/base stability (pH tolerance: −0.778–15.079), surpassing all prior TOCs. Mechanistic studies, supported by stepwise balanced chemical equations, reveal water’s dual role in pyrazolylborate formation: mediating dehydration condensation and cluster nucleation, thus bridging organic–inorganic co-assembly. As a biosensor, 2,4-2FTi₈@rGO/GCE electrode delivers benchmark electrochemical performance for chlorogenic acid (CGA), featuring ultrahigh sensitivity (9.486 μA·μM⁻¹), nanomolar detection limit (6.59 nM) and a wide linear range (0.1–140 μM). It represents one of the few examples that simultaneously integrates all these key performance advantages. Theoretical calculations indicate that the stronger adsorption of 2,4-2FTi₈ toward reaction species leads to its better electrochemical detection performance than MeBTi₄. This work establishes a synthetic paradigm for TOCs via organic–inorganic co-assembly and highlights their electrochemical sensing potential.