The proposal that paramagnetic transition metal complexes could be used as qubits for quantum information processing (QIP) requires that the molecules retain the spin information for a sufficient length of time to allow computation and error correction. Therefore, understanding how the electron spin-lattice relaxation time (T₁) and phase memory time (T_m) relate to structure is important. Previous studies have focused on the ligand shell surrounding the paramagnetic centre, seeking to increase rigidity or remove elements with nuclear spins or both. Here we have studied a family of early 3d or 4f metals in the +2 oxidation states where the ground state is effectively a ²S state. This leads to a highly isotropic spin and hence makes the putative qubit insensitive to its environment. We have studied how this influences T₁ and T_m and show unusually long relaxation times given that the ligand shell is rich in nuclear spins and non-rigid.

Air pollution by nitrogen oxides, NO_x, is a major problem, and new capture and abatement technologies are urgently required. Here, we report a metal-organic framework (Manchester Framework Material 520 (MFM-520)) that can efficiently confine dimers of NO₂, which results in a high adsorption capacity of 4.2 mmol g^-1 (298 K, 0.01 bar) with full reversibility and no loss of capacity over 125 cycles. Treatment of NO₂@MFM-520 with water in air leads to a quantitative conversion of the captured NO₂ into HNO₃, an important feedstock for fertilizer production, and fully regenerates MFM-520. The confinement of N₂O₄ inside nanopores was established at a molecular level, and the dynamic breakthrough experiments using both dry and humid NO₂ gas streams verify the excellent stability and selectivity of MFM-520 and confirm its potential for precious-metal-free deNO_x technologies.

Hydrogen bonds dominate many chemical and biological processes, and chemical modification enables control and modulation of host-guest systems. Here we report a targeted modification of hydrogen bonding and its effect on guest binding in redox-active materials. MFM-300(V^III) {[V^III₂(OH)₂(L)], LH₄=biphenyl-3,3',5,5'-tetracarboxylic acid} can be oxidized to isostructural MFM-300(V^IV), [V^IV₂O₂(L)], in which deprotonation of the bridging hydroxyl groups occurs. MFM-300(V^III) shows the second highest CO₂ uptake capacity in metal-organic framework materials at 298 K and 1 bar (6.0 mmol g^-1) and involves hydrogen bonding between the OH group of the host and the O-donor of CO₂, which binds in an end-on manner, =1.863(1) Å. In contrast, CO₂-loaded MFM-300(V^IV) shows CO₂ bound side-on to the oxy group and sandwiched between two phenyl groups involving a unique ···c.g._phenyl interaction [3.069(2), 3.146(3) Å]. The macroscopic packing of CO₂ in the pores is directly influenced by these primary binding sites.

Ammonia (NH₃) is a promising energy resource owing to its high hydrogen density. However, its widespread application is restricted by the lack of efficient and corrosion-resistant storage materials. Here, we report high NH₃ adsorption in a series of robust metal-organic framework (MOF) materials, MFM-300(M) (M = Fe, V, Cr, In). MFM-300(M) (M = Fe, V^III, Cr) show fully reversible capacity for >20 cycles, reaching capacities of 16.1, 15.6, and 14.0 mmol g^-1, respectively, at 273 K and 1 bar. Under the same conditions, MFM-300(V^IV) exhibits the highest uptake among this series of MOFs of 17.3 mmol g^-1. In situ neutron powder diffraction, single-crystal X-ray diffraction, and electron paramagnetic resonance spectroscopy confirm that the redox-active V center enables host-guest charge transfer, with V^IV being reduced to V^III and NH₃ being oxidized to hydrazine (N₂H₄). A combination of in situ inelastic neutron scattering and DFT modeling has revealed the binding dynamics of adsorbed NH₃ within these MOFs to afford a comprehensive insight into the application of MOF materials to the adsorption and conversion of NH₃.