Directional Shunting of Photogenerated Carriers in POM@MOF for Promoting Nitrogen Adsorption and Oxidation

Abstract

Abstract The efficient catalysis of nitrogen (N 2 ) into high‐value N‐containing products plays a crucial role in the N economic cycle. However, weak N 2 adsorption and invalid N 2 activation remain two major bottlenecks in rate‐determining steps, leading to low N 2 fixation performance. Herein, an effective dual active sites photocatalyst of polyoxometalates (POMs)‐based metal–organic frameworks (MOFs) is highlighted via altering coordination microenvironment and inducing directional shunting of photogenerated carriers to facilitate N 2 /catalyst interaction and enhance oxidation performance. MOFs create more open unsaturated metal cluster sites with unoccupied d orbital possessing Lewis acidity to accept electrons from the 3 σ g bonding orbital of N 2 for storage by combining with POMs to replace bidentate linkers. POMs act as electron sponges donating electrons to MOFs, while the holes directional flow to POMs. The hole‐rich POMs with strong oxidation capacity are easily involved in oxidizing adsorbed N 2 . Taking UiO‐66 (C 48 H 28 O 32 Zr 6 ) and Mo 72 Fe 30 ([Mo 72 Fe 30 O 252 (CH 3 COO) 12 {Mo 2 O 7 (H 2 O)} 2 {H 2 Mo 2 O 8 (H 2 O)}(H 2 O) 91 ]·150H 2 O) as an example, Mo 72 Fe 30 @UiO‐66 shows twofold enhanced adsorption of N 2 (250.5 cm 3 g −1 ) than UiO‐66 (122.9 cm 3 g −1 ) at P / P 0 = 1. And, the HNO 3 yield of Mo 72 Fe 30 @UiO‐66 is 702.4 µg g −1 h −1 , ≈7 times and 24 times higher than UiO‐66 and Mo 72 Fe 30 . This work provides reliable value for the storage and relaying artificial N 2 fixation.