Poly(heptazine imide) ligand exchange enables remarkable low catalyst loadings in heterogeneous metallaphotocatalysis

Abstract

The development of heterogeneous metallaphotocatalysis is of great interest for sustainable organic synthesis. The rational design and controllable preparation of well-defined (site-isolated) metal/photo bifunctional solid catalysts to meet such goal remains a critical challenge. Herein, we demonstrate the incorporation of privileged homogeneous bipyridyl-based Ni-catalysts into highly ordered and crystalline potassium poly(heptazine imide) (K-PHI). A variety of PHI-supported cationic bipyridyl-based Ni-catalysts (LnNi-PHI) have been prepared and fully characterized by various techniques including NMR, ICP-OES, XPS, HAADF-STEM and XAS. The LnNi-PHI catalysts exhibit exceptional chemical stability and recyclability in diverse C−P, C−S, C−O and C−N cross-coupling reactions. The proximity and cooperativity effects in LnNi-PHI significantly enhances the photo/Ni dual catalytic activity, thus resulting in low catalyst loadings and high turnover numbers.

Revealing the mechanism of charge storage induced hole catalysis

“…The x-ray diffraction (XRD) spectra of the prepared PHI material show the characteristic peaks consistent with the literature (Fig. 4e) [48][49][50][51][52][53] . Moreover, PHI material prepared by different methods exhibits nearly identical vibrational modes (Supplementary Fig.…”

Defective Potassium Poly(Heptazine Imide) Preventing Spin Delocalization and Hole Transfer Deactivation for Efficient Solar Energy Conversion and Storage

“…The charge transfer properties of BKM and BKCN were further investigated by electrochemical impedance spectroscopy (EIS) and transient photocurrent response measurements. [ 10–12 ] As shown in Figure S7a, Supporting Information, smaller circular arcs are observed from the Nyquist plots of BKM compared to BKCN both in the dark and under illumination, indicating lower charge transfer resistance in BKM. Moreover, Figure S7b, Supporting Information reveals a more substantial photocurrent density acquired from BKM than BKCN.…”

“…[7] The PHI-based DOI: 10.1002/smll.202304813 carbon nitrides with superior performances for various photocatalytic reactions have been reported recently. [8][9][10][11][12][13] 2D PHI-based carbon nitrides are usually produced by an ionothermal process in the presence of potassium slats, forming cyanamidefunctionalized potassium poly(heptazine imide) (KPHI). [1][2][3][4][5][6][7][8][9] Under illumination, the photogenerated electrons are stored in KPHI with the existence of hole scavengers to generate the KPHI radical which usually exhibits blue or green color.…”

Copper-doped carbon nitride as a practical heterogeneous metallaphotocatalyst for aerobic oxidative cross-coupling of tertiary amines with terminal alkynes

“…As a class of solid-state sensitizer materials, carbon nitride (CN) 8 has been exploited as not only a particularly attractive catalyst for visible-light-mediated organic transformations, given the merits of convenient synthesis and excellent stability, but also an appealing host option due to its heptazine units containing intrinsic coordination sites. 9–12 In particular, K-modified carbon nitride (CN–K) easily synthesized by the molten salt template method has a well-defined negative poly(heptazine imide) layer structure with K + ions as charge compensation, which provides the possibility of exchange between K + and metal ions in the matrix. 12 c ,13 Herein, we describe our effort toward the use of this cation exchange strategy to construct a Cu-doped carbon nitride (CN–Cu) material, which can serve as a fully heterogeneous photo–Cu bifunctional catalyst for the direct α-alkynylation of tertiary amines using air as an oxidant.…”