Two Novel Hydrogen-Bonded Metal–Organic Frameworks: Dual Functions for Reversible Hydrochromism and Electrocatalytic Hydrogen Evolution Reaction
Hua Liu, He-Juan Li, Zhi-Wei Zheng, Bo-Yi Fu, Xiang‐Yu Zhang, Kun Huang, Da‐Bin Qin, Bin Zhao
Abstract
Metal–organic frameworks (MOFs) with versatile functions are attractive in broad fields based on unique structures and properties. Here, two isomorphic MOFs defined as {[M(dibpca) 2 (H 2 O) 2 ]·3H 2 O·DMF} n (M = Co ( 1 ), Ni ( 2 ), H-dibpca = 3′,5′-di(1 H -imidazol-1-yl)-[1,1′-biphenyl]-4-carboxylic acid) have been constructed, innovatively showing dual functions on chromism and electrocatalysis. The MOFs are networks consisting of 1D chains connected by nine types of hydrogen bonds. Upon dehydration/rehydration, 1 exhibits a more intelligent reversible chromic behavior via diverse pathways when compared to 2 with different metal nodes. Notably, the highly sensitive hydrochromism of 1 can be used for qualitative detection of water content in organic solvents ranging from 0 to 20% and can be repeated at least 10 times, presenting an instant, naked-eye visible and reusable detection tool. The conspicuous color variations are caused by the release/reuptake of coordinated waters, as confirmed by TGA and in situ FT-IR. In addition, the compounds also perform well in electrocatalytic hydrogen evolution reaction (HER) via water splitting. When loaded on carbon paper (CP) as a working electrode, 1 and 2 display high electrocatalytic HER activities with low overpotentials (195 and 207 mV) and Tafel slopes (107 and 93 mV dec –1 ), which is outstanding among pristine bulk MOF catalysts. The diverse functions of hydrogen-bonded MOFs facilitate the design and construction of functional complexes as well as the development of practical applications.