Synergistic Cu₂ and Polyoxometalate Clusters in Metal-Organic Layers Enable Oxidant-Free CH₄ Photooxidation.

Abstract

Methane (CH₄) photooxidation under mild conditions represents a transformative approach for sustainable production of fuel and chemicals, however, it remains challenging due to the persistent requirement for exogenous oxidants. Herein, this study reports a series of well-defined bicluster photocatalysts Cu₂POF_Mn/PCN-n (n = 1/5/8/10, denoting the mass ratio of PCN: Cu₂POF_Mn), constructed by integrating [Cu(µ₂-I)]₂ (denoted as Cu₂) clusters and MnMo₆ polyoxometalates (POMs) within ultrathin metal-organic layers (MOLs) anchored on PCN nanoflakes. The optimized Cu₂POF_Mn/PCN-8 photocatalyst achieves efficient CH₄ conversion to HCOOH with 10.5 mmol g_POF ^-1 yield and 95% selectivity without any exogenous oxidant. Comprehensive studies demonstrated that the engineered MOLs architecture enables uniform and ordered assembly of complementary catalytic bicluster, where MnMo₆ POMs act as electron reservoirs to promote charge separation for in situ H₂O₂ generation, and Cu₂ clusters mimic CH₄ monooxygenase to selectively cleave C-H bonds via forming Cu₂-O···H···CH₃ intermediate. This work highlights the vital role of MOL-directed bicluster assembly for C-H functionalization that bypasses the need for sacrificial oxidants in selective CH₄ functionalization.