Binderless shaped metal-organic framework particles: Impact on carbon dioxide adsorption

Binderless metal-organic framework (MOF) particles were shaped by mechanical compression of commercial ZIF-8 and MIL-53(Al) powders. Two compression pressures were employed - 62 MPa and 125 MPa - and their impact in the mechanical, structural, and textural characteristics of the MOFs were evaluated. The impact on carbon dioxide (CO2) adsorption capacity at 303 K was also evaluated. The shaped MOF particles are robust and able to withstand PSA-like pressure cycles up to 18 bar. Mechanical compression has much higher impact on the crystalline and textural properties of MIL-53(Al) than on those of ZIF-8; the latter exhibited surface area and pore volume losses as low as 7% relative to the MOF powder, whereas the best case of shaped MIL-53(Al) particles decreased the surface area and pore volume by 32% and 24%, respectively. Mercury porosimetry shows that the compressed ZIF-8 particles exhibit macropores and large mesopores with narrow size distribution. The compressed MIL-53(Al) powder gave rise to smaller intercrystalline pores with wider size distribution than the ZIF-8 samples. The shaping procedure has minor impact on the CO2 adsorption capacity of the ZIF-8 particles compared to the uncompressed powder, with no difference up to 8 bar of CO2 pressure and a capacity loss below 6% at 29 bar. The MIL-53(Al) granules yielded higher CO2 adsorption capacity losses: 24% and 22% at 15 bar of CO2 pressure for compressions at 62 MPa and 125 MPa, respectively. The results reported herein show that this method is a viable alternative for the preparation of ZIF-8 and MIL-53(Al) particles for application in gas-phase separation processes.