Covalent Organic Frameworks (COFs), an emerging class of crystalline porous materials,are proposed as anew type of support for grafting lanthanide ions (Ln 3+ )a nd employing these hybrid materials as ratiometric luminescent thermometers.ATpBpy-COF-prepared from 1,3,5-triformylphloroglucinol (Tp) and 2,2'-bipyridine-5,5'-diamine (Bpy) grafted with Eu/Tb and Dy acetylacetone (acac) complexes can be successfully used as al uminescent thermometer in the 10-360 K( Eu) and 280-440 K( Tb) ranges with good sensing properties (thermal sensitivity up to 1.403 %K À1 ,t emperature uncertainty dT < 1Kabove110 K). Forthe Eu/Tb systems,we observe an unusual and rarely reported behavior,t hat is,n o thermal quenching of the Tb 3+ emission, aresult of the absence of ion-to-ligand/host energy back-transfer.T he LnCOF materials proposed here could be anew class of materials employed for temperature-sensing applications following up on the wellknownluminescent metal-organic framework thermometers.

Covalent Organic Frameworks (COFs), an emerging class of crystalline porous materials, are proposed as a new type of support for grafting lanthanide ions (Ln3+) and employing these hybrid materials as ratiometric luminescent thermometers. A TpBpy‐COF—prepared from 1,3,5‐triformylphloroglucinol (Tp) and 2,2′‐bipyridine‐5,5′‐diamine (Bpy) grafted with Eu/Tb and Dy acetylacetone (acac) complexes can be successfully used as a luminescent thermometer in the 10–360 K (Eu) and 280–440 K (Tb) ranges with good sensing properties (thermal sensitivity up to 1.403 % K−1, temperature uncertainty δT<1 K above 110 K). For the Eu/Tb systems, we observe an unusual and rarely reported behavior, that is, no thermal quenching of the Tb3+ emission, a result of the absence of ion‐to‐ligand/host energy back‐transfer. The LnCOF materials proposed here could be a new class of materials employed for temperature‐sensing applications following up on the well‐known luminescent metal–organic framework thermometers.

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