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Tailoring porosity and rotational dynamics in a series of octacarboxylate metal-organic frameworks

DOI: 10.1073/pnas.1615172114 DOI Help

Authors: Florian Moreau (University of Manchester) , Daniil I. Kolokolov (Russian Academy of Sciences; Novosibirsk State University) , Alexander G. Stepanov (Russian Academy of Sciences; Novosibirsk State University) , Timothy L. Easun (Cardiff University) , Anne Dailly (General Motors Corporation) , William Lewis (University of Nottingham) , Alexander J. Blake (University of Nottingham) , Harriott Nowell (Diamond Light Source) , Matthew J. Lennox (University of Nottingham) , Elena Besley (University of Nottingham) , Sihai Yang (University of Manchester) , Martin Schröder (University of Manchester; Russian Academy of Sciences)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 114 , PAGES 3056-3061

State: Published (Approved)
Published: March 2017
Diamond Proposal Number(s): 12517

Abstract: Modulation and precise control of porosity of metal-organic frameworks (MOFs) is of critical importance to their materials function. Here we report modulation of porosity for a series of isoreticular octacarboxylate MOFs, denoted MFM-180 to MFM-185, via a strategy of selective elongation of metal-organic cages. Owing to the high ligand connectivity, these MOFs do not show interpenetration, and are robust structures that have permanent porosity. Interestingly, activated MFM-185a shows a high Brunauer–Emmett–Teller (BET) surface area of 4,734 m2 g−1 for an octacarboxylate MOF. These MOFs show remarkable CH4 and CO2 adsorption properties, notably with simultaneously high gravimetric and volumetric deliverable CH4 capacities of 0.24 g g−1 and 163 vol/vol (298 K, 5–65 bar) recorded for MFM-185a due to selective elongation of tubular cages. The dynamics of molecular rotors in deuterated MFM-180a-d16 and MFM-181a-d16 were investigated by variable-temperature 2H solid-state NMR spectroscopy to reveal the reorientation mechanisms within these materials. Analysis of the flipping modes of the mobile phenyl groups, their rotational rates, and transition temperatures paves the way to controlling and understanding the role of molecular rotors through design of organic linkers within porous MOF materials.

Journal Keywords: metal-organic framework; copper; CO2; CH4; molecular rotors

Subject Areas: Chemistry


Instruments: I19-Small Molecule Single Crystal Diffraction