Zn-regulated electronic configuration triggering 100% selectivity switch between CO and CH4 for photocatalytic CO2 reduction

Herein, a bimetallic zinc-cobalt metal-organic framework (ZnCoMOF) microsphere cluster with abundant oxygen vacancies was rationally designed and synthesized for visible-light-driven photocatalytic CO 2 reduction. XPS results reveal that the substitution of Co 3 + by Zn 2+ modulated the electronic structure of Co sites, reduced the Co 3+ /Co 2+ ratio, and generated electron-rich Co 2+ centers as well as oxygen vacancies. The reversible Co 3+ /Co 2+ redox pair accelerates charge migration, while oxygen vacancies inhibit carrier recombination. Moreover, electron-enriched Co 2+ favor CO 2 activation. The synergistic effect of multiple active centers optimizes reaction kinetics and catalytic performance. The optimized Zn 0.3 Co 1 MOF delivered a CO yield 2.21 times as high as that of pristine CoMOF, reaching 5.33 mmol g −1 within 4 h, and it achieved an ultrahigh CO selectivity of 100%. The enhanced performance benefits from Zn-induced electronic modulation and synergistic catalysis. Notably, in a diluted CO 2 atmosphere, the product composition exhibits an obvious transition from CO to CH 4 with the decrease in CO 2 concentration. Lower CO 2 concentration contributes to a higher CH 4 yield and greater CH 4 selectivity in the products. Under 20% CO 2 atmosphere, the CH 4 production reached 0.36 mmol g −1 within 4 h with an ultra-high CH 4 selectivity of 100%. These results indicate that in the Zn x Co 1 MOF-catalyzed CO 2 reduction system, product selectivity can be readily modulated by adjusting CO 2 concentration. This offers a facile strategy for the efficient utilization of low-concentration CO 2 from industrial flue gas. Download: Download high-res image (394KB) Download: Download full-size image