Selective anion extraction is useful for the recovery and purification of valuable chemicals, and in the removal of pollutants from the environment. Here we report that Fe^II₄L₄ cage 1 is able to extract an equimolar amount of ReO₄⁻, a high‐value anion and a nonradioactive surrogate of TcO₄⁻, from water into nitromethane. Importantly, the extraction was efficiently performed even in the presence of 10 other common anions in water, highlighting the high selectivity of 1 for ReO₄⁻. The extracted guest could be released into water as the cage disassembled in ethyl acetate, and then 1 could be recycled by switching the solvent to acetonitrile. The versatile solubility of the cage also enabled complete extraction of ReO₄⁻ (as the tetrabutylammonium salt) from an organic phase into water by using the sulfate salt of 1 as the extractant.

Here we demonstrate how the hydrogen-bonding ability of a BINOL-based dialdehyde subcomponent dictated the stereochemical outcome of its subsequent self-assembly into one diastereomeric helicate form when bearing free hydroxy groups, and another in the case of its methylated congener. The presence of methyl groups also altered the self-sorting behavior when mixed with another, short linear dialdehyde subcomponent, switching the outcome of the system from narcissistic to integrative self-sorting. In all cases, the axial chirality of the BINOL building block also dictated helicate metal center handedness during stereospecific self-assembly. A new family of stereochemically pure heteroleptic helicates were thus prepared using the new knowledge gained. We also found that switching from Fe^II to Zn^II, or the incorporation of a longer linear ligand, favored heteroleptic structure formation.

Here we report the subcomponent self‐assembly of a truxene‐faced Zn₄L₄tetrahedron, which is capable of binding the smallest hydrocarbons in solution. By deliberately incorporating inward‐facing ethyl groups on the truxene faces, the resulting partially‐filled cage cavity was tailored to encapsulate methane, ethane, and ethene via van der Waals interactions at atmospheric pressure in acetonitrile, and also in the amorphous solid state. Interestingly, gas capture showed divergent selectivities in solution and the amorphous solid state. The selective binding may prove useful in designing new processes for the purification of methane and ethane as feedstocks for chemical synthesis.

The use of di(2‐pyridyl)ketone in subcomponent self‐assembly is introduced. When combined with a flexible triamine and zinc bis(trifluoromethanesulfonyl)imide, this ketone formed a new Zn₄L₄ tetrahedron 1 bearing twelve uncoordinated pyridyl units around its metal‐ion vertices. The acid stability of 1 was found to be greater than that of the analogous tetrahedron 2 built from 2‐formylpyridine. Intriguingly, the peripheral presence of additional pyridine rings in 1 resulted in distinct guest binding behavior from that of 2, affecting guest scope as well as binding affinities. The different stabilities and guest affinities of capsules 1 and 2 enabled the design of systems whereby different cargoes could be moved between cages using acid and base as chemical stimuli.