Electron diffraction (3DED) data of MFU-4-Br were collected using a Rigaku XtaLAB Synergy-ED system equipped with a Rigaku HyPix-ED detector and LaB6 electron source operating at 200 keV (λ = 0.0251 Å) in a vacuum at ambient temperature with the side entry grid holder. Data collection and processing, i.e., structure refinements, data reductions, and analysis were performed using the Rigaku Oxford Diffraction CrysAlis Pro program package. The shutterless data, 500 frames of 0.2 deg width, was recorded in continuous crystal rotation mode (3D-ED/MED) at the 645 mm detector distance using the selected area configuration. The samples were placed on a standard amorphous carbon on a Cu grid and transferred to a holder at ambient temperature. The initial object search, electron beam sensitivity tests, selection and centering of crystal, and first measurements were performed also at the transfer temperature. Due to the high symmetry of the crystal structures, dataset merging was not required. The collected data was processed and finalized with frame scaling and empirical correction up to 0.7 Å resolution. To verify phase purity of the bulk sample, the structure model obtained from electron diffraction measurements was used as the initial model for the Rietveld method. The powder sample was measured in reflection geometry on a Rigaku SmartLab XE diffractometer, equipped with a PhotonMax Cu rotating anode (Xray generator: 9 kW, 45 kV, 200 mA) and a HyPiX-3000 2-D detector. Measurement was conducted using an HTK 1200N Anton Paar Temperature Oven Chamber at 120°C under vacuum conditions. Prior to data collection, the sample was heated for 4.5 hours at 120°C. Data were recorded in the 2θ range of 5-90° with an angular step width of 0.01° and a speed of 1°C•min -1 . Ambient X-ray powder diffraction (XRPD) patterns were collected using a Seifert XRD 3003 TT diffractometer with a Meteor1D detector using Cu Kα1 radiation (λ=1.54187). Variable temperature X-ray powder diffraction data were measured in the 5-60° 2θ range under nitrogen atmosphere with an Empyrean (PANalytical) diffractometer equipped with a Bragg-Brentano HD mirror and a PIXcel3D 2x2 detector. The temperature program carried out in 50 °C steps up 700 °C included a heating rate of 0.05 K•s -1 and then 10 min isothermal between the measurements. The thermogravimetric analysis of the gas loaded samples was performed with a TGA Q500 analyser in the temperature range of 25-600 °C or 25-700 °C under nitrogen atmosphere at a heating rate of 10 K•min -1 . The temperature modulated thermogravimetric analysis was performed with the same instrument. The measurement was carried out under a helium atmosphere at a heating rate of 1.5 K•min -1 , amplitude of ± 5 °C and period of 200 s. The gas release kinetics at different heating rates was studied with a BelCat-B catalyst analyzer (Bel Japan, Inc.) coupled with a mass spectrometer (OmniStar GSD 320, Pfeiffer Vacuum). The sample was placed between two plugs of quartz wool in a quartz glass reactor and heated up to 300 °C at a constant heating rate (1, 3, 5 or 7 K•min -1 ) under a flow of helium ). The composition of the exhaust gas was analyzed by a mass spectrometer. SEM micrographs were recorded on a scanning electron microscope (LEO Zeiss, Gemini 982). The structure of MFU-4-Br was elucidated by both electron diffraction measurement and Rietveld refinement (for details see Supporting Information). MOF synthesis MFU-4, [Zn5Cl4(bbta)3]n: The MOF was prepared by microwaveassisted synthesis by upscaling the procedure reported by us previously. A mixture of anhydrous ZnCl2 (340 mg, 2.495 mmol) and H2-BBTA (100 mg, 0.624 mmol) in DMF (5 mL) was placed in a Pyrex sample tube (30 mL). The reaction mixture was heated in a microwave synthesizer (CEM, Discover S) to 155 °C at 300 W, kept under these conditions for 10 min, and then cooled to ambient temperature. The formed precipitate was isolated by centrifugation, washed with DMF (3 x 5 mL) and dried in air at ambient conditions to give an off-white crystalline material (166 mg). The reaction was carried out several times to produce enough material and to ensure its reproducibility. Prior to the gas loading experiments, the as-synthetized sample (166 mg) was kept under vacuum at 320 °C for 24 h to remove any solvent molecules from the pores resulting in 122 mg of an activate material (yield: 62 %). FT-IR: ν = 1437 (w), 1411 (m), 1315 (m), 1212 (s), 1193 (s), 1031 (w), 866 (s), 779 (w), 434 (s), 394 (m), 246 (s), 231 (s) and 213 (s) cm -1 .