Surface ligand‐removed and Cd‐rich CdSe quantum dots (QDs) exhibited exceptional activity as photocatalyst for the conversion of CO2 to CO. A CO production rate up to 789 mmol g−1 h−1 was achieved in a triethylamine/dimethylformamide mixture under visible‐light irradiation. Mechanistic studies revealed that improving the Cd/Se stoichiometric ratio and exposing more active surface Cd atoms significantly enhanced the activity of CdSe QDs for CO2 photoreduction.

The conversion of CO2 and protons to solar fuels (CO and H2) is achieved by CoN4 active sites anchored on SiO2.

The conversion of carbon dioxide (CO) to fuels or value-added chemicals by a photocatalytic system has recently been of growing research interest. One of the challenges is the development of new catalysts with high activity and low cost. Cobalt complexes have long been used as catalysts for the reduction of CO in either electrochemical or photochemical systems. Recently, a series of cis-Co complexes of tetradentate pyridine-amine ligands (N-ligands) exhibited high activity in the reduction of CO in homogeneous photocatalytic systems. However, only CO was obtained as the reduction product. In this regard, herein, we report a novel cis-Co complex C1 supported by an N ligand derivatized with TPA (TPA = tris(2-pyridylmethyl)amine). In contrast to the aforementioned Co catalysts, which contain two halogen atoms at cis-positions, C1 contains one oxygen atom at one cis-coordination site. The structure of C1 was fully characterized by MS, elemental analysis, and single-crystal X-ray diffraction. Experiments on the photocatalytic reduction of CO revealed that C1 is able to convert CO to not only CO but also formate in a homogeneous system containing C1 as a catalyst, Ir(ppy) as a photosensitizer, and triethylamine as an electron donor under visible-light irradiation. The catalytic activity and distribution of reduction products of this system are highly affected by the solvent environment. The presence of water in this system enhances the efficiency of 2H-to-H and CO-to-formate conversions. Electrochemical and steady-state emission quenching experiments indicate that photoinduced electron transfer from excited Ir(ppy) to C1 is thermodynamically feasible. A photogenerated Co species is suggested to be the active species involved in the reduction of CO and protons. DFT calculations were performed to elucidate the catalytic pathways of the formation of CO, formate, and H in this system; four pathways, namely, one for the formation of CO, one for the formation of hydrogen, and two for the formation of formate, were suggested. The results revealed that the oxygen atom at the cis-coordination site in C1 plays an important role in stabilizing the transition state during the transformation of CO at the cobalt center.

Interlayer excitons (IXs) in type II van der Waals (vdW) heterostructures are equipped with an oriented permanent dipole moment and long lifetime and thus would allow promising applications in excitonic and optoelectronic devices. However, based on the widely studied heterostructures of transition-metal dichalcogenides (TMDs), IX emission is greatly influenced by the lattice mismatch and geometric misalignment between the constituent layers, increasing the complexity of the device fabrication. Here, we report on the robust momentum-indirect IX emission in TMD/two-dimensional (2D) perovskite vdW heterostructures, which were fabricated without considering the orientation arrangement or momentum mismatch. The IXs show a large diffusion coefficient of ∼10 cm 2 s −1 , and importantly the IX emission energy can be widely tuned from 1.3 to 1.6 eV via changing the layer number of the 2D perovskite or the thickness of TMD flakes, shedding light on the applications of vdW interface engineering to broad-spectrum optoelectronics.

Self-trapped excitons, which often occurs in materials with soft lattice and strong electron–phonon coupling, have attracted a lot of attention owing to their unique broadband emission and promising applications in persistent white light sources. However, the emission of self-trapped excitons is usually weak in some two-dimensional (2D) and three-dimensional (3D) perovskites because of their low radiative recombination rate. The existing strategies of enhancing the emission efficiency of self-trapped excitons such as metal cation doping and organic ligands modification often entail complex chemical synthetic processes. Here, we report a new approach to significantly boost the self-trapped exciton emission via the interfacial excitonic energy transfer in 2D/quantum dots (QDs) perovskite heterostructures. The self-trapped exciton emission in the heterostructures could be enhanced more than two orders of magnitude compared with the constituent 2D perovskite crystals. Temperature-, excitation power- and thickness-dependent photoluminescence (PL) studies reveal that the enhanced self-trapped exciton emission in the heterostructure can be ascribed to Dexter energy transfer taking place at the interface of the heterostructure. Our study provides a simple and practical interface-based strategy to improve the emission efficiency of self-trapped excitons for photoelectric devices.