A rational synthetic strategy to construct two supramolecular isomers based on polyoxovanadate organic polyhedra with tetrahedral symmetries is presented. VMOP‐α, a low‐temperature product, has an extremely large cell volume (470 842 Å3), which is one of the top three for well‐defined MOPs. The corner‐to‐corner packing of tetrahedra leads to a quite low density of 0.174 g cm−3 with 1D channels (ca. 5.4 nm). The effective pore volume is up to 93.6 % of cell volume, nearly the largest found in MOPs. For the high‐temperature outcome, VMOP‐β, the cell volume is only 15 513 Å3. The packing mode of tetrahedra is corner‐to‐face, giving rise to a high‐density architecture (1.324 g cm−3; channel 0.8 nm). Supramolecular structural transformation between VMOP‐α and VMOP‐β can be reversibly achieved by temperature‐induced solvent‐mediated transformation. These findings give a good opportunity for understanding 3D supramolecular aggregation and crystal growth based on large molecular tectonics.

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SnTe is an emerging Pb‐free thermoelectric compound that has drawn significant attention for clean energy conversion. Chemical doping is routinely used to tailor its charge carrier concentration and electronic band structures. However, the efficacy of dopants is often limited by their small solubility. For example, only 0.5% Ag can be incorporated into the SnTe matrix. Yet, significantly more Ag (>7%) can be dissolved if SnTe is alloyed with AgSbTe2. This large enhancement of solubility can be understood from a chemical bonding perspective. Both SnTe and AgSbTe2 employ metavalent bonding as identified by an unusual bond‐rupture in atom probe tomography. Density functional theory calculations show that upon Ag doping the energy offset of the upmost two valence bands decreases significantly. This induces band alignment in SnTe, which results in an enhanced power factor over a broad temperature range. Moreover, the increased concentration of point defects and associated lattice strain lead to strong phonon scattering and softening, contributing to an extremely low κL of 0.30 Wm−1K−1. These synergistic effects contribute to a peak ZT of 1.8 at 873 K and a record‐high average ZT of ≈1.0 between 400 and 873 K in Sn0.87Mn0.08Sb0.08Te–5%AgSbTe2 alloy.

Unprecedented Anderson-like alkoxo-polyoxovanadate [V6O6(OCH3)9(μ6-SO4)(COO)3](2-) polyanions can serve as 3-connected second building units (SBUs) that assemble with dicarboxylate or tricarboxylate ligands to form a new family of metal organic tetrahedrons of V4E6 and V4F4 type (V = vertex, E = edge, and F = face). To our knowledge, this alkoxo-polyoxovanadate-based SBU is the first ever reported.