Integrating High-Density Frustrated Lewis Pairs with Switchable Pt–O–In Motifs to Break the Activity–Selectivity Trade-Off of Methane Photooxidation

Abstract

The direct photooxidation of methane to value-added products presents a promising solution for the utilization of abundant natural gas resources. However, there are still great challenges in the production of multiple oxidation products and inevitable overoxidation owing to the difficult manipulation of C–H bond activation and alternative radical formation. Herein, the high-density In(L)-O v -In-OH frustrated Lewis pairs (FLPs) with Lewis acidic In(L) and Lewis basic In-OH were constructed on the Pt-mIn 2 O 3– x (OH) y photocatalyst to promote the C–H bond activation in CH 4 . In situ characterization techniques and theoretical calculations revealed that the electron transfer from the bonding orbitals (σ) of CH 4 to the unoccupied orbitals of In(L), coupled with the weak electron donation from the In-OH sites to the antibonding orbitals (σ*) of CH 4, cooperatively polarized and stretched the C–H bond, thus significantly lowering its dissociation energy barrier. Meanwhile, the tailored Pt–O–In motifs (either Pt nanoparticles or Pt single atoms) on the Pt-mIn 2 O 3– x (OH) y photocatalyst serving as an electron acceptor could precisely modulate the types of reactive oxygen species by altering the adsorption configuration of O 2 . Benefiting from the synergy of the In(L)-O v -In-OH FLPs and Pt motifs, both excellent yield and selectivity were obtained for CH 3 OH or HCHO. Under optimal conditions, Pt nanoparticles supported on mIn 2 O 3– x (OH) y (Pt NPs -mIn 2 O 3– x (OH) y ) achieved a high CH 3 OH production rate of 3970.0 μmol g –1 h –1 with 90.9% selectivity, and Pt single atoms coordinated with mIn 2 O 3– x (OH) y (Pt SAs -mIn 2 O 3– x (OH) y ) delivered an excellent HCHO yield of 10182.4 μmol g –1 h –1 with 84.9% selectivity. This work demonstrated a promising strategy for designing advanced photocatalysts to disentangle the activity–selectivity trade-off in CH 4 photooxidation.