Zero-Dimensional-g-CNQD-Coordinated Two-Dimensional Porphyrin MOF Hybrids for Boosting Photocatalytic CO2 Reduction

It is urgent yet challenging to develop photocatalysts for visible-light-driven CO2 reduction with high efficiency and selectivity. Here, we report a novel hybrid catalyst by coordinating zero-dimensional (0D) carbon nitride quantum dots (g-CNQDs) with two-dimensional (2D) ultrathin porphyrin MOF (PMOF). Different from previously reported hybrid catalysts combined through physical or electrostatic interactions, in our prepared g-CNQDs/PMOF hybrids, g-CNQDs are coordinated with Co active sites in PMOF, which significantly shortens the migrating pathway of both photogenerated charge carriers and gaseous substrates from g-CNQDs to Co active centers. The resulting efficient electron-hole pair separation and long-lived trapped electrons at Co centers not only boost the photocatalytic CO2 reduction activity but also improve its selectivity for the eight-electron reduced product CH4. To our knowledge, this is the first example of a hybrid catalyst combined through coordination interaction. Remarkably, the prepared hybrid catalyst exhibits a 2.34-fold enhancement in the CO generation rate (16.10 μmol g-1 h-1) and a 6.02-fold enhancement in the CH4 evolution rate (6.86 μmol g-1 h-1) compared to the bare PMOF.