金属有机框架中的光响应金属有机多面体:实现“真正”的响应

Photoresponsive metal-organic polyhedra in metal-organic frameworks:Achieving“real”responsiveness

光响应金属有机多面体(PMOP)在吸附、催化和分子包裹等应用中显示出可控的性质,但PMOP的聚集导致分子无法进入其内部的纳米笼并且光调节效率低.本工作合成了一种具有偶氮苯侧基的新型光响应MOP(PM_(2)L_(4)),并将其分散到金属有机框架(MOF,PCN-333)的孔道中.制备的PM_(2)L_(4)@MOF复合材料显示出明显改善的CO_(2)捕获能力和光响应效率.在可见光照射下,偶氮苯基团处于反式构型,CO_(2)分子可以自由进入PM_(2)L_(4)的纳米空间.在紫外光照射下,偶氮苯基团转变为顺式构型并阻碍CO_(2)进入PM_(2)L_(4).在紫外/可见光的交替照射下,PM_(2)L_(4)的偶氮苯基团能够实现可逆的顺式-反式转化.在光照调节下,PM_(2)L_(4)@MOF复合材料对CO_(2)的吸附变化为15.5%,远高于聚集态的PM_(2)L_(4)(5.9%).

Photoresponsive metal-organic polyhedra(PMOPs)show controllable properties in a broad range of applications,such as adsorption,catalysis,and molecule inclusion.However,the aggregation of bulk PMOPs leads to their inaccessibility of inside nanocages and low regulatory efficiency by light.Herein,a new PMOP(PM_(2)L_(4))with pendant azobenzene units was synthesized and dispersed into the pores of the metal-organic framework(MOF,PCN-333).The obtained PM_(2)L_(4)@MOF composites show improved CO_(2)uptake and photoresponsive efficiency.Upon visible-light irradiation,the azobenzene groups stay in the trans state where CO_(2)molecules can freely enter the nanospace of PM_(2)L_(4).Nevertheless,upon ultraviolet(UV)-light irradiation,the azobenzene groups transform to the cis state,which hinders the entrance of CO_(2)to the nanospace of PM_(2)L_(4).In addition,UV/visible light irradiation can facilitate the reversible cis-/trans-isomerization of the azobenzene groups of PM_(2)L_(4).The adsorption variation of CO_(2)captured by PM_(2)L_(4)@MOF composite under light is 15.5%,which is much higher than that of bulk PM_(2)L_(4)(5.9%).We believe that the findings of this study will provide insights into the potential of PMOPs and may inspire the development of exquisite strategies to efficiently control adsorption processes.