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.

The electrocatalytic conversion of nitrate to ammonia has made significant progress as a promising strategy for removing NO₃⁻ and producing NH₃. However, there is a lack of an efficient electrocatalyst to achieve highly selective NH₃ synthesis under low concentration NO₃⁻ conditions. In this study, we design and synthesize a bimetallic copper-containing metal-organic framework (MOF) (CuInL₄, L = 4-(4-pyridyl)benzoic acid), named InCu-MOF, which possesses 2-fold interpenetrating structure and high-density catalytic sites. InCu-MOF is the first MOF catalyst applied to NH₃ synthesis at low NO₃⁻ concentration. Benefiting from the regulation of electronic properties and synergistic catalytic effects of two metal active sites, InCu-MOF exhibits high catalytic activity for the low concentration of NO₃⁻ reduction reaction (NO₃RR) for the first time. At a potential of −1.0 V (vs. RHE), InCu-MOF achieves NH₃ faradaic efficiency (FE) of 82% and yield rate of 892 µg·h⁻¹·mg_cat⁻¹, which FE is 2.6-fold and yield rate are 8.1-fold higher than that of In-MOF. The design and synthesis of this interpenetrating bimetallic MOF provides an idea for the construction of an efficient catalyst at low NO₃⁻ concentrations.