Tunable Emission And White Light Emitting Properties Of Host-Guest Composites Based On Porous Framework

Solid-state White light-emitting diodes（WLEDs）have been widely studied and applied in lighting,display and other fields because of their merits of high efficiency,energy saving,long life-time and environmental friendliness.At present,most of the commercial phosphors are rare earth doped.However,due to the low abundance of rare earth resources,high price,and easy to cause environmental problems,so researching and developing phosphors without rare earth is of great significance.Among numerous framework materials,porous framework materials have been widely applied in gas adsorption and separation,catalysis,luminescent and magnetism,drug delivery and other aspects due to their advantages of porosity,highly adjustable structure and size,and abundant luminescent centers.In this paper,the strategy of introducing guest luminescent units into the porous framework material was explored on the basic of the synthesis of porous framework.By adjusting the amount of host framework and guest units,the fluorescence spectra and the emission color of the composite materials were regulated,and the single-phase yellow phosphors which can be applied in WLED were prepared.This paper is mainly divided into the following three contents:（1）Single-phase single-shell CQDs&Rh B@ZIF-8² and single-phase multi-shell CQDs@ZIF-8²@Rh B@ZIF-8² were fabricated by epitaxial growth.In this work,an ultra-robust metal-organic framework,ZIF-8 was selected as the host framework,the green emitting carbon quantum dots（CQDs）and the red emitting Rhodamine B（Rh B）were chosen as the guest luminescent units.Single phase single-shell CQDs&Rh B@ZIF-8²,as well as single phase multi-shell CQDs@ZIF-8²@Rh B@ZIF-8²,were fabricated and fine-tuned so that the emitting color is near that of the commercial yellow-emitting phosphor.It is found that the multi-shell structure of CQDs@ZIF-8²@Rh B@ZIF-8² provided sufficient spatial separation for the two guest units and effectively weakened the energy transfer between CQDs and Rh B.Therefore,it has higher quantum efficiency than that of the CQDs&Rh B@ZIF-8² composites.By coating the composite materials on commercially available blue chips,the fabricated WLED lamps exhibits bright white light emitting upon applying a working voltage of 3.0 V and a current of 500 m A.This work provides a new strategy to obtain yellow phosphors with higher quantum efficiency in the future.（2）Rh B@γ-CD-MOF@Cs Pb Br3@γ-CD-MOF composite materials with multi-shell structure were designed.In order to obtain phosphors with higher quantum efficiency,we choseγ-CD-MOF as the host framework,the highly luminescent green light emitting Cs Pb Br₃ perovskite quantum dots and the red light emitting rhodamine B were chosen as guest luminescent units.By secondary epitaxial growth method,the two guest luminescent units were encapsulated in the different shells ofγ-CD-MOF,and the yellow composite material with high quantum efficiency（QY≈43.5%）was successfully synthesized.By assembling the yellow phosphor with commercially available Ga N blue chips（450 nm）,the WLED diodes with bright white light emitting can be obtained.It has certain guiding significance for preparing highly luminescent yellow phosphors which can be applied in WLED.（3）Dye@PFC-1 nanocomposite materials were fabricated by impregnation method.In this work,Rh B,Rh6G,DSM and DCM dye molecules were encapsulated into the channels of PFC-1,a robust green light-emitting hydrogen-bonded organic framework respectively.A series of dye@PFC-1 nanocomposite materials with broadband yellow light emission were prepared by regulating the fluorescence spectra and luminescent color of the composite materials.After coating the yellow phosphor on the commercially available blue chips,warm white light emission with low color temperature and high color rendering index were obtained,which was very suitable for indoor lighting.At present,HOF-based composite materials for white light emission are still in its infancy.Therefore,our strategy provides a new perspective for the preparation of high-performance warm white LED.