Jeremiah P. Tidey

Mechanochemistry enables the elimination of highly toxic solvents in the synthesis of porous metal–organic polyhedra.

3D ED is used to study the structures of solvent-exchanged phases in zinc paddlewheel-based MOPs.

Zinc paddlewheels are widely found in metal-organic frameworks, but found more sparingly in porous molecules. Here we report some of the first examples of metal-organic polyhedra containing zinc paddlewheels, where structural adaptations in the cages have been observable thanks to the use of 3D electron diffraction.

We investigate the properties of CuVOF 4 ( H 2 O ) 6 · H 2 O , in which two different spin species, Cu(II) and V(IV), form antiferromagnetic spin-1/2 dimers with weak interdimer coupling provided via hydrogen bonding. Using radio-frequency susceptometry and electron-spin resonance (ESR), we show how the temperature-magnetic field spin-dimer phase diagram evolves as a function of applied hydrostatic pressure and correlate this with pressure-induced changes to the crystal structure. These results, coupled with pressure-tuned DFT calculations, confirm the prior prediction that the primary exchange interaction is mediated via an unusual mechanism in which the V(IV) ions provide considerable spin density to the oxygen that joins the two spins in each dimer and which lies along the Jahn-Teller axis of the Cu(II) ion. In addition, the dissimilarity in the spins that make up each dimer unit leads to a nonlinear field dependence of the electronic energy levels as detected in the ESR measurements.

Metal-organic polyhedra (MOPs) are the porous molecular counterparts to metal-organic frameworks (MOFs). While mechanochemistry has been successfully applied to a wide range of MOFs, this synthetic approach has found more limited use for MOPs. Herein, two mechanochemical routes have been developed for a series of MOPs presenting a lantern geometry. The cages can be formed through: Route 1, grinding with DMA, and therefore achieving a reduction in solvent usage of 90%; or through Route 2, grinding with MeOH to completely eliminate the use of non-volatile, highly toxic solvents. The development of Route 2 is facilitated by 3D electron diffraction, which proved the formation of discrete cages that would otherwise be inaccessible through direct solvothermal synthesis. The degree of crystallinity in all cases of the mechanochemical products is equal or superior to material obtained through solvothermal methods, and presents comparable porosity. As well as presenting a method for improving the sustainability of the synthesis of these cages, this work extends the range of porous cages to which mechanochemistry can be applied. Given the known dependence of the porosity of MOPs on the crystal packing of their parent solvated forms, Route 2 suggests that future work could probe the formation of new solvated phases that display distinct gas sorption behaviour.

Enzyme encapsulation within a 2D layered metal–organic framework stabilizes enzymes that are otherwise prone to aggregation and practical handling difficulties, whilst maintaining good reactant access to the enzyme.

A Ce( iii ) 2,5-furandicarboxylate framework forms under solvothermal conditions in N , N -dimethylformamide; subsequent expose to water leads to recrystallisation into a structurally distinct coordination polymer.

Porous metal‐organic polyhedra (MOPs) have strong covalent and coordinate bonds that define the intrinsic pore of the cage. The intermolecular interactions between cages tend to be weaker, such that they rearrange during the solvent exchange process preceding gas sorption measurements. The reduction in crystal size that this often causes limits the availability of structural data that could enable understanding of observed gas uptake. Herein, we use 3D electron diffraction (ED) to resolve this problem, and apply this technique to a MOP‐based material that shows cooperative gas capture. 3D ED structure solution reveals both that the MOPs rearrange to form porous 1D polymers, and that these polymers are retained in the activated phase. Molecular simulations using these data suggest gas uptake is facilitated by rotation of functional groups appended to the backbone of the polymers in conjunction with structural expansion as gas is accommodated. Mechanical downsizing of the material leads to the loss of cooperative gas uptake, but a level of porosity is retained, attributed to the conservation of the 1D polymer structure. This work underscores the potential of 3D ED for probing structural transformations in functional supramolecular materials.

Porous metal‐organic polyhedra (MOPs) have strong covalent and coordinate bonds that define the intrinsic pore of the cage. The intermolecular interactions between cages tend to be weaker, such that they rearrange during the solvent exchange process preceding gas sorption measurements. The reduction in crystal size that this often causes limits the availability of structural data that could enable understanding of observed gas uptake. Herein, we use 3D electron diffraction (ED) to resolve this problem, and apply this technique to a MOP‐based material that shows cooperative gas capture. 3D ED structure solution reveals both that the MOPs rearrange to form porous 1D polymers, and that these polymers are retained in the activated phase. Molecular simulations using these data suggest gas uptake is facilitated by rotation of functional groups appended to the backbone of the polymers in conjunction with structural expansion as gas is accommodated. Mechanical downsizing of the material leads to the loss of cooperative gas uptake, but a level of porosity is retained, attributed to the conservation of the 1D polymer structure. This work underscores the potential of 3D ED for probing structural transformations in functional supramolecular materials.

Van der Waals metal-organic magnets (vdW MOMs) offer the possibility of realis- ing a wide-range of magnetic functionalities not possible in inorganic vdW magnets. In particular, they offer the opportunity to enhance magnetic interactions using organic functionalisation to control ligand energy levels directly. We report a new vdW MOM, CrCl2(btd) (btd = 2,1,3-benzothiadiazole), assembled from a high energy early transi- tion metal and a redox-active ligand, which leads to a small charge-transfer gap. We solve the structure using a combination of powder neutron diffraction and single crystal electron diffraction, showing that this material contains Cr2+btd0. Magnetometry, neutron diffraction and inelastic neutron scattering allow us to quantitatively determine the magnetic properties of this vdW magnet, showing it is a collinear rectangular antiferromagnetwithsmalleasyaxisanisotropy(JCl =−15.31(5)K,Jbtd =−6.96(10)K, D = −2.0(2) K). Critically, we find that the superexchange through the redox-active btd is significantly stronger than in the non-redox-active CrCl2(pym) (pym = pyrimidine) analogue (Jpym = 1.2(2)K), demonstrating that exchange can be enhanced without the need for electron transfer onto ligands. This work provides a route towards vdW MOMs with strong magnetic superexchange.