Protesescu Loredana, Calbo Joaquín, Williams Kristopher, Tisdale William, Walsh Aron, Dincă Mircea
Department of Chemistry, Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge Massachusetts 02139 USA
Department of Materials, Imperial College London London SW7 2AZ UK.
Chem Sci. 2021 Mar 19;12(17):6129-6135. doi: 10.1039/d1sc00282a.
The development of synthetic routes to access stable, ultra-small ( <5 nm) lead halide perovskite (LHP) quantum dots (QDs) is of fundamental and technological interest. The considerable challenges include the high solubility of the ionic LHPs in polar solvents and aggregation to form larger particles. Here, we demonstrate a simple and effective host-guest strategy for preparing ultra-small lead bromide perovskite QDs through the use of nano-sized MOFs that function as nucleating and host sites. CrO(OH)(HO)(terephthalate) (Cr-MIL-101), made of large mesopore-sized pseudo-spherical cages, allows fast and efficient diffusion of perovskite precursors within its pores, and promotes the formation of stable, ∼3 nm-wide lead bromide perovskite QDs. CsPbBr, MAPbBr (MA = methylammonium), and (FA)PbBr (FA = formamidinium) QDs exhibit significantly blue-shifted emission maxima at 440 nm, 446 nm, and 450 nm, respectively, as expected for strongly confined perovskite QDs. Optical characterization and composite modelling confirm that the APbBr (A = Cs, MA, FA) QDs owe their stability within the MIL-101 nanocrystals to both short- and long-range interfacial interactions with the MOF pore walls.
开发能够获得稳定的、超小（<5纳米）的卤化铅钙钛矿（LHP）量子点（QD）的合成路线具有重要的基础研究意义和技术价值。其中存在的重大挑战包括离子型LHP在极性溶剂中的高溶解性以及聚集形成更大的颗粒。在此，我们展示了一种简单有效的主客体策略，通过使用作为成核和主体位点的纳米级金属有机框架（MOF）来制备超小的溴化铅钙钛矿量子点。由大孔尺寸的伪球形笼构成的CrO(OH)(HO)(对苯二甲酸)（Cr-MIL-101），能使钙钛矿前驱体在其孔内快速高效扩散，并促进形成稳定的、约3纳米宽的溴化铅钙钛矿量子点。CsPbBr、MAPbBr（MA = 甲基铵）和(FA)PbBr（FA = 甲脒）量子点分别在440纳米、446纳米和450纳米处表现出显著蓝移的发射最大值，这对于强受限的钙钛矿量子点来说是预期的。光学表征和复合建模证实，APbBr（A = Cs、MA、FA）量子点在MIL-101纳米晶体内的稳定性归因于与MOF孔壁的短程和长程界面相互作用。
