Polydopamine-coated metal-organic framework-based composite phase change materials for photothermal conversion and storage

The liquid leakage and weak solar absorption capacity of organic phase change materials(PCMs)seriously hinder the efficient utilization of solar energy and thermal energy storage.To address these issues,we prepared nanoporous metal organic framework(Ni-MOF)for the vacuum infiltration of paraffin wax(PW),followed by the coating of solar-absorbing functional polydopamine(PDA)on the surface of PW@MOF for photothermal conversion and storage.As an efficient photon harvester,PDA coating endows PW@MOF/PDA composite PCMs with excellent photothermal conversion and storage properties due to the robust broadband solar absorption capability in the UV–vis region.Resultantly,our prepared PW@MOF/PDA composite PCMs exhibit a high photothermal conversion and storage efficiency of 91.2%,while that of PW@MOF composite PCMs is only zero.In addition,PW@MOF/PDA composite PCMs also exhibit excellent thermal stability,shape stability,energy storage stability,and photothermal conversion stability.More importantly,this coating strategy is universal by integrating different MOFs and solar absorbers,showing the potential to accelerate the major breakthroughs of high-efficiency MOF-based photothermal composite PCMs in solar energy utilization.

Polypyrrole-boosted photothermal energy storage in MOF-based phase change materials

Infiltrating phase change materials(PCMs)into nanoporous metal–organicframeworks(MOFs)is accepted as a cutting-edge thermal energy storageconcept.However,weak photon capture capability of pristine MOF-basedcomposite PCMs is a stumbling block in solar energy utilization.Towards thisgoal,we prepared advanced high-performance pristine MOF-based photothermalcomposite PCMs by simultaneously integrating photon absorber guest(polypyrrole[PPy])and thermal storage guest(1-octadecanol[ODA])intoan MOF host(Cr-MIL-101-NH2).The coated PPy layer on the surface ofODA@MOF not only serves as a photon harvester,but also serves as a phononenhancer.Resultantly,ODA@MOF/PPy composite PCMs exhibit intense andbroadband light absorption characteristic in the ultraviolet–visible–nearinfraredregion,and higher heat transfer ability than ODA@MOF.Importantly,the photothermal conversion and storage efficiency of ODA@MOF/PPy-6%is up to 88.3%.Additionally,our developed MOF-based photothermalcomposite PCMs also exhibit long-standing antileakage stability,energystorage stability,and photothermal conversion stability.The proposed coatingstrategy and in-depth understanding mechanism are expected to facilitate thedevelopment of high-efficiency MOF-based photothermal composite PCMs insolar energy utilization.