Pt nanoparticles embedded in flowerlike NH2-UiO-68 for enhanced photocatalytic carbon dioxide reduction

Abstract

Stabilizing metal nanoparticles (MNPs) with metal–organic frameworks (MOFs) has become a favorable pathway for developing efficient hybrid photocatalysts, while effective charge transfer within hybrid catalysts is largely elusive. In this work, we employed a semiconductor-like Zr-MOF, NH₂-UiO-68, with an amino-functionalized linker and permanent porosity enabling the confinement of guest species for the first time. Pt NPs have been embedded inside (referred to as Pt@MOF), outside (referred to as Pt/MOF) or both inside and outside (referred to as Pt-MOF) of the flowerlike NH₂-UiO-68 by varying synthetic methods and Pt NP amounts. Among these different hybrids, the 2 wt% Pt@NH₂-UiO-68 sample presents the highest photocatalytic CO₂ reduction activity under visible light irradiation, and is far superior to the 2 wt% Pt/NH₂-UiO-68, 1 wt% Pt@NH₂-UiO-68, and 4 wt% Pt-NH₂-UiO-68 samples. The appropriate location and content of Pt NPs in the catalysts would facilitate the contact between Pt NPs and NH₂-UiO-68, which is beneficial to form Pt-MOF heterojunctions, thereby achieving efficient charge transfer in the photocatalytic process. More importantly, effective charge transfer from NH₂-UiO-68 to the excited Pt NPs via Pt-MOF Schottky junctions can accordingly inhibit the recombination of photogenerated charge carriers, ultimately leading to the enhancement of photocatalytic activity.