Synthesis of the composites of carbon quantum dots and metal organic framework and their application in hydrogen evolution

Abstract

The Ti-MIL-125 metal-organic framework (MOF) functions as a nanoreactor, producing carbon quantum dots (CQDs) within its structure and forming CQD/MOF composites. Similarly, a Pt-CQD/MOF three-component composite is synthesized. Their properties, along with those of CQDs and MOF-free-CQDs (mf-CQDs) enclosed within the MOF, undergo assessment and comparison. Integrating CQDs and Pt minimally alters the MOF structure but reduces specific surface areas due to incorporation. The emitted wavelength of CQD/MOF (570 nm) differs from pristine CQDs (450 nm) and mf-CQDs (496 nm), indicating MOF influence on CQDs' growth and photoluminescence. HOMO and LUMO levels of CQDs/MOF, measured via ultraviolet photoelectron spectroscopy and low-energy inverse photoelectron spectroscopy, are more positive than those of the MOF, suggesting heterogeneous junction formation, aiding electron separation. CQD/MOF exhibits a modest photocatalytic hydrogen evolution rate of 20.4 μmol/g/h. Conversely, Pt-CQD/MOF significantly boosts the rate to 2213 μmol/g/h, underscoring Pt's pivotal catalytic role.