abstract
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.
keywords
INITIO MOLECULAR-DYNAMICS; TOTAL-ENERGY CALCULATIONS; CRYSTALLITE SIZE; SPIN-CROSSOVER; DRIVEN; CO2; POROSITY; DISCRETE; DESIGN
subject category
Chemistry
authors
Snelgrove, MP; Suso, BD; Sangster, CS; Asif, K; Martí, ER; Ashworth, DJ; Tidey, JP; Gomes, JRB; Jorge, M; Kennedy, AR; Parsons, S; Fletcher, AJ; Craig, GA
our authors
José R. B. Gomes
Principal ResearcherProjects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
M.P.S., A.J.F., and G.A.C. thank the Leverhulme Trust for the award of the Leverhulme Trust Research Project Grant RPG-2022-004. E.R.M., A.J.F., and G.A.C. thank the LeverhulmeTrust for the award of the Leverhulme Trust Research Project Grant RPG-2022-173. B.D.S. and G.A.C. thank the University of Strathclyde for the award of a 3-year PhDstudentship to B.D.S. SP thanks the Leverhulme Trust forthe Research Project Grant RPG-2021-176, and EPSRC forstudentship funding for C.S.S. K.A. and M.J. thank EPSRC and the National Physical Laboratory for the award of aniCASE PhD studentship (ref. EP/Y528833/1). G.A.C. thanksScotCHEM for the award of the ScotCHEM ECR equipmentfunding call 2022, which supported the purchase of the ballmill used in this study. G.A.C and M.P.S. thank Dr CatherineE. Weetman for experimental assistance in activating samplesfor PXRD measurements. The authors acknowledge that thepowder X-ray diffraction data were collected in the CMACNational Facility, within the University of Strathclyde'sTechnology and Innovation Centre, funded with a UKRPIF(UK Research Partnership Institute Fund) capital award, SFCref. H13054, from the Higher Education Funding Council forEngland (HEFCE). J.R.B.G. is thankful to project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020,UIDP/50011/2020 and LA/P/0006/2020, financed by nationalfunds through the FCT/MCTES (PIDDAC). The authorsthank the NCS for granting rapid access to the NationalElectron Diffraction Facility under EPSRC funding(EP/X014606/1 & EP/X014444/1, A National ElectronDiffraction Facility for Nanomaterial Structural Studies), as well as the University of Warwick X-ray Research TechnologyPlatform for provision of further analysis facilities.