Hierarchical Integration of Photosensitizing Metal–Organic Frameworks and Nickel‐Containing Polyoxometalates for Efficient Visible‐Light‐Driven Hydrogen Evolution

Abstract

Metal–organic frameworks (MOFs) provide a tunable platform for hierarchically integrating multiple components to effect synergistic functions that cannot be achieved in solution. Here we report the encapsulation of a Ni‐containing polyoxometalate (POM) [Ni 4(H 2 O)2(PW 9 O 34)2]10− (Ni 4 P 2) into two highly stable and porous phosphorescent MOFs. The proximity of Ni 4 P 2 to multiple photosensitizers in Ni 4 P 2@MOF allows for facile multi‐electron transfer to enable efficient visible‐light‐driven hydrogen evolution reaction (HER) with turnover numbers as high as 1476. Photophysical and electrochemical studies established the oxidative quenching of the excited photosensitizer by Ni 4 P 2 as the initiating step of HER and explained the drastic catalytic activity difference of the two POM@MOFs. Our work shows that POM@MOF assemblies not only provide a tunable platform for designing highly effective photocatalytic HER catalysts but also facilitate detailed mechanistic understanding of HER processes.