Bimetallic MIL-68(InFe) MOF nanorods for biomimetic photocatalytic N2 fixation

This work develops a series of bimetallic MIL-68(InFe) MOF nanorods (NM(In 1-x Fe x )) mimicking the nitrogenase for biomimetic photocatalytic N 2 fixation. The partial substitution of In 3+ with Fe 3+ leads to the electron redistribution from In 3+ to Fe 3+ , generating electron-poor In 3+ (In (3+δ)+ ) sites and electron-rich Fe 3+ (Fe (3–δ)+ ) sites as an electron acceptor–donor combination to promote the N 2 activation by a π back-donation mechanism. The smaller size of the nanorods further provides more accessible active sites than the bulk counterpart. In cooperation with the H + released from the H 2 O, the activated N 2 molecules were reduced by photogenerated electrons to give NH 3 . The optimal sample NM(In 0.90 Fe 0.10 ) exhibited the highest NH 4 + production rate of 30.8 µmol·h −1 ·g −1 without any sacrificial agent, attributed to the presence of abundant In/Fe bimetallic sites for N 2 activation and enhanced charge mobility. This work provides new insights into rational design for artificial N 2 fixation systems by mimicking natural nitrogenase.