Synthesis of confined palladium nanocatalysts in crystalline hemoglobin framework: An ultrastable nanoreactor for Cr(VI) detoxification

In this work, cross-linked hemoglobin crystals (CLHCs) were synthesized using discarded cow blood as raw material, and palladium nano particles (Pd NPs) was synthesized in situ within its lattice to obtain CLHCs@Pd catalytic used for catalyzing the reduction of Cr(VI). In addition, we investigated the influence of synthesis process on the morphology, loading capacity, and size of Pd NPs, and the results showed that the minimum size of Pd NPs was distributed around 2 nm under any process conditions. The X-ray single crystal diffraction results indicate that the lattice of protein crystals may have a controlling effect on the size of Pd NPs. Subsequently, the mechanism of synthesizing Pd NPs by CLHCs was studied using techniques such as SEM, TEM, FTIR and XPS. Finally, the catalytic activity and cycling performance of Cr(VI) removal by CLHCs@Pd were evaluated. The results indicate that the CLHCs@Pd not only exhibit high catalytic activity for Cr(VI) removal, but also maintain consistent catalytic performance over 20 consecutive catalytic cycles. Overall, this work provides CLHCs@Pd catalysts have the following advantages: (1) small size and uniform dispersion of Pd NPs; (2) High cycling performance and high catalytic activity; (3) Low cost and environmentally friendly preparation process.