High-efficient solar-driven nitrogen fixation by modulating the internal electric-field of MOFs via n-site-enhanced charge density difference in organic ligands

[Display omitted] •A strategy to construct MOF with high charge density difference ligands was proposed.•Three Zr-MOFs with different charge density ligands were designed and prepared.•N sites in ligands were used to change the internal electric-field of photocatalysts.•The interactions between light and photocatalysts have been numerically studied.•Zr-PzDC yields 143.51 μmol·g−1·h−1 NH4+ under ambient conditions. N2 photofixation at ambient conditions plays a key role in environmental stability on earth. Based on the strategy that introducing N sites to change the charge distribution of organic ligands to regulate the internal electric-field, three types of MOFs by doping different organic ligands, namely Zr-PzDC, Zr-PyDC and Zr-BDC were designed and synthesized to fix nitrogen for obtaining enhanced photocatalytic performance. DFT calculations show that the pyrazine ring in Zr-PzDC has a larger charge density difference, which is beneficial to the separation and transmission efficiency of photogenerated electrons and expands the photoresponse range. The surface charge density of the samples was numerically calculated by using the field-only surface integral method. Zr-PzDC demonstrated the best nitrogen photofixation performance of 143.51 μmol·g−1·h−1 under ambient conditions. This study provides a new approach and perspective for the design of MOF photocatalysts for N2 fixation based on designing different organic ligands structure.