Disentangling the Photocatalytic Hydrogen Evolution Mechanism of One Homogeneous Cobalt-Coordinated Polymer

One novel cobalt-coordinated graphitic carbon nitride-type polymer (Co-g-CN) integrating the advantages of both molecular catalytic efficiency and nano semiconductor stability was fabricated, which served as homogeneous photocatalyst exhibiting superior hydrogen evolution efficiency (ca. ∼ 12.3 mmol g–1 h–1) under visible light irradiation in the absence of noble metal cocatalyst. Various techniques including laser photolysis and electron paramagnetic resonance were combined to disentangle the underlying photocatalytic mechanism, which suggested that, unlike nano semiconducting catalysis, the multivalent Co metal center of the polymer mediated the electron transfer process, directly got involved in the proton reduction by sequentially exchanging electrons in a way similar to those molecular coordinated catalysts. These findings provide useful insight into the photocatalytic mechanism of the metal center-mediated water splitting process, and the employment of an economical non-noble metal-coordinated polymer as highly efficient catalyst may open a new avenue for long-term conversion of sunlight into sustainable hydrogen energy.