Measuring the Efficiency of Photoinduced Electron Transfer at the Perovskite@Metal–Organic Framework Buried Interfaces

Metal halide perovskite nanocrystals exhibit remarkable semiconductor characteristics with continuously tunable optical band gap covering almost all of the visible spectrum that imbue numerous prospective applications, including the field of photocatalysis. The ease of synthesis, significant efficiency of light absorption and emission, and remarkable charge transport characteristics offer many exciting possibilities to unravel the specific physicochemical attributes to ameliorate in a diverse range of niche applications. However, the stability of the perovskite quantum dots (PQDs) in aqueous medium is an important issue, as the naked nanostructures are highly sensitive to environmental conditions. Among the different approaches to engendering the intrinsic stability issue of perovskite nanostructures, the encapsulation of perovskites within the interpenetrating structures of metal–organic frameworks (MOFs) can be alleviated as a viable solution to this problem. We demonstrate the crystallization of CsPbBr₃ QDs within the pore metal–organic frameworks based on earth-abundant elements such as Cr, Fe, and Ti as the matrices and investigated the photocatalytic activities toward the degradation of methyl orange as the model reaction. The CsPbBr₃ QDs within the nanocavities of metal–organic frameworks have been synthesized using a ship-in-bottle strategy and characterized through a series of spectroscopic and microscopic techniques. Upon encapsulation within the pores, the photogenerated electrons of CsPbCl₃ QDs can be transferred to the metal catalytic sites of the MOF structures with a longer carrier lifetime on the nanosecond time scale. The turnover frequency has been calculated as 27, 15, and 22 mol g^–1 h^–1 in the presence of CsPbBr₃@MIL-101-Cr, CsPbBr₃@MIL-101-Fe, and CsPbBr₃@MIL-125-Ti nanohybrids, respectively. The buried heterojunctions formed at the perovskite@MOF nanohybrids decrease the trap density and, thus, increase the mobilities of the electrons and holes that enhance carrier extraction and suppress charge recombination. Therefore, the concept of utilizing the photoinduced electron transfer at the perovskite–MOF interface toward the degradation of organic pollutants could pave an avenue for plausible industrial applications.