Calcination-free 3D printed structured CuO-ZnO-ZrO₂ catalysts for efficient CO₂ hydrogenation to methanol fuel

The hydrogenation of CO₂ to methanol is a promising route for carbon recycling and low-carbon fuel synthesis, yet practical deployment of CuO–ZnO–ZrO₂ (CZZ) catalysts is hindered by performance losses during catalyst shaping and high-temperature calcination. Herein, a calcination-free route was developed to fabricate structured CZZ catalysts by combining direct ink writing (DIW) and freeze-drying. A water-based printable ink comprising CZZ, cellulose nanocrystals (CNCs) as binder, and cellulose-derived porous carbon (CNCdPC) as functional additive enabled stable extrusion and produced grid-like architectures with sufficient mechanical integrity after freeze-drying, without any thermal post-treatment. The freeze-dried structured catalysts exhibited uniform, unbroken wire diameters of 450 ± 50 μm, and vertical through-holes that reduced diffusion resistance. Structural and surface characterization confirmed that freeze-drying suppressed crystallite growth, preserved surface oxygen vacancies, and maintained the intrinsic Cu-Zn-Zr interfacial structure, while CNCdPC incorporation enhanced microporosity and CO₂ adsorption capacity. Consequently, the optimized structured catalyst achieved a methanol space–time yield of 357 g_MeOH/kg_cat/h at 220°C and 3 MPa, with stable performance over 72 h, whereas conventional CZZ powder gave 162 g_MeOH/kg_cat/h even at 240°C. This work demonstrates that calcination-free additive manufacturing provides an effective strategy for shaping thermally sensitive catalysts, offering a scalable route toward efficient methanol fuel production from CO₂.