Tailored Zr bio-MOF structures for CO₂ adsorption: A comparative study of binderless pelletization and chitosan-based...

An ultra-microporous, bio-based zirconium metal-organic framework (MIP-202), was successfully synthesized and formulated into compressed pellets and extrudates through incorporation with the biopolymer chitosan, targeting efficient CO₂ adsorption. The effects of formulation pressure and the addition of chitosan as a co-binder were systematically investigated to optimize the physical integrity and performance of the shaped adsorbents. Comprehensive physicochemical characterizations were conducted using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) surface area analysis. The formulated pellets and extrudates demonstrated excellent thermal stability, good mechanical durability, and retention of their ultra-microporous structure (<1 nm) after formulation. Remarkably, they preserved up to 99 % of the CO₂ adsorption capacity of the pristine powder form (18.7 cm³ g^-1 at 298 K and 1 bar), with a low isosteric heat of adsorption (30-40 kJ mol^-1), which also facilitates easy CO₂ desorption and enhances regeneration efficiency. Furthermore, they exhibited a high CO₂/N₂ (15/85, v/v), towards CO₂ with a selectivity ratio of 24-25 under dry and humid conditions. The materials maintained moderate moisture stability over 20 days, strong resistance in N₂O environments, and excellent cyclic stability over 10 temperature swing adsorption (TSA) cycles. Combined with the low cost of the MOF bio-ligand, L-aspartic acid (∼$36/kg), these findings highlight the potential of MIP-202 pellets and extrudates as robust and economically viable candidates for industrial flue gas separation applications.