Selection of binder recipes for the formulation of MOFs into resistant pellets for molecular separations by fixed-bed adsorption

Recent advances in process engineering and upcoming applications of metal–organic frameworks

“…Before S. A. After Process time Ref Polyvinyl group MIL-125-NH 2 97% 1259 930 – [154] Polyvinyl alcohol (PVA) UiO-66 22 vol% 710 359 30 min [155] Polysiloxane UiO-66 72.5 vol% 710 418 30 min [155] Polyvinyl Butyral (PVB) SIFSIX-3-Ni – 360 297 – [156] Polyvinyl Butyral (PVB) SIFSIX-2-Cu-i – 808 685 – [156] Polyvinyl Butyral (PVB) GeFSIX-2-Cu-i – 755 659 – [156] Polyvinyl Butyral (PVB) TIFSIX-2-Cu-i – 740 719 – [156] Polyvinyl Butyral (PVB) Mg-MOF-74 – 915 – – [156] Polyvinyl Butyral (PVB) HKUST-1 – – – – [156] Polyvinylchloride (PVC) ZIF-8 7.5 / 15 / 30 wt% – – – [157] Polyvinylformal (PVF) ZIF-8 7.5 / 15 / 30 wt% – …”

“…Shaping using polymer-type binders has been the most widely studied. Specifically, polymer binders with polyvinyl groups such as Polyvinyl group [154] , [155] , [156] , [157] , polyetherimide (PEI) [157] , polystyrene (PS) [157] , cellulose-acetate (CA) [157] , acrylonitrile butadiene styrene [158] , sucrose [159] and TENAX [160] have been combined with MOFs for shaping. Typically, polymer binders are the first choice for MOF shaping because i) they are easy to dissolve in volatile dispersion media, making mixing and drying of the MOF powder relatively simple; ii) they have various chemical bonding groups, and thus the degree of interaction between the chemical functionalities and dangling components of the MOF particles can be controlled; iii) there are many precedents for the use of polymers as binders with other classes of porous materials, such as activated carbon and zeolites, which increases the probability of shaping success; and iv) compared with inorganic binders, organic binders have relatively low weights, and thus the weight of the binder required for shaping is low, which is advantageous in terms of performance per unit weight.…”

“… a. Non-pressurized processes without binders Process type MOF Ratio of MOF/Binder Forming Pressure Shape Ref High-internal-phase emulsion (HIPE) & freeze drying HKUST-1 < 3.0 wt% – Monolith [169] Sol-gel ZIF-8HT 100 wt% – Monolith [171] Sol-gel ZIF-8LT 100 wt% – Monolith [171] Sol-gel ZIF-8LT-HT 100 wt% – Monolith [171] Sol-gel ZIF-8ER 100 wt% – Monolith [171] Oil-drop granulation UiO66 100 wt% – Granules (sphere) [172] Xero gel UiO-66 70% – Monolith [172] b. Pressurized processes with binders Process type MOF Ratio of MOF/Binder Forming Pressure shape Ref Extrusion-crushing-sieving (ECS) ZIF-8 – 65 MPa Pellet [157] Pressing MOF-5 – – Pellet [166] …”

“…In [157] , ZIF-8 and polymer binders such as polyvinylchloride (PVC), polyvinylformal (PVF), PEI, PS, and CA were formed into composite pellets by extrusion. First, the composite of ZIF-8 and binder was prepared by controlling the amount of binder and gradually adding solvent until a thick slurry was obtained.…”

From metal–organic framework powders to shaped solids: recent developments and challenges

“…The study by Cousin-Saint-Remi et al [86] addressed the careful choice of binder for the preparation of mechanically stable extrudates from ZIF-8 powder, a MOF demonstrating a relative stability upon more constraining processes such as pelletization (table 3). Within the scope of their study, a series of binders were tested but only a few yielded robust objects.…”