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

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.