Electronic Tuning of CO 2 Interaction by Oriented Coordination of N-Rich Auxiliary in Porphyrin Metal-Organic Frameworks for Light-Assisted CO 2 Electroreduction.

The efficient CO 2 electroreduction into high-value products largely relies on the CO 2 adsorption/activation or electron-transfer of electrocatalysts, thus site-specific functionalization methods that enable boosted related interactions of electrocatalysts are much desired. Here, an oriented coordination strategy is reported to introduce N-rich auxiliary (i.e., hexamethylenetetramine, HMTA) into metalloporphyrin metal organic frameworks (MOFs) to synthesize a series of site-specific functionalized electrocatalysts (HMTA@MOF-545-M, M = Fe, Co, and Ni) and they are successfully applied in light-assisted CO 2 electroreduction. Noteworthy, thus-obtained HMTA@MOF-545-Co presents approximately two times enhanced CO 2 adsorption-enthalpy and electrochemical active surface-area with largely decreased impedance-value after modification, resulting in almost twice higher CO 2 electroreduction performance than its unmodified counterpart. Besides, its CO 2 electroreduction performance can be further improved under light-illumination and displays superior FE CO (≈100%), high CO generation rate (≈5.11 mol m -2  h -1 at -1.1 V) and energy efficiency (≈70% at -0.7 V). Theoretical calculations verify that the oriented coordination of HMTA can increase the charge density of active sites, almost doubly enhance the CO 2 adsorption energy, and largely reduce the energy barrier of rate determining step for the boosted performance improvement. This work might promote the development of modifiable porous crystalline electrocatalysts in high-efficiency CO 2 electroreduction.