Highly Crystalline and Porous Borocarbonitrides as Metal-Free Catalysts for Boosted N-Heterocycle Dehydrogenation

Abstract

Safe and efficient hydrogen storage is pivotal for enabling a clean hydrogen economy. Liquid organic hydrogen carriers (LOHCs) offer a practical solution, but their deployment is hindered by the lack of highly active and economical dehydrogenation catalysts. Here, we report a metal-free catalyst design that overcomes the long-standing trade-off between crystallinity and surface area in two-dimensional frameworks for highly efficient dehydrogenation of LOHCs. A flux-assisted reconstruction strategy transforms amorphous borocarbonitrides (AM-BCN) into highly crystalline, defect-rich BCN nanosheets (C-BCN) with large surface area and accessible porosity, as confirmed by complementary spectroscopic, x-ray, and neutron analyses. C-BCN catalyzes the acceptor-less dehydrogenation of aza-fused LOHCs with quantitative hydrogen release under mild conditions, outperforming AM-BCN and previously reported metal-free scaffolds. Mechanistic insights from x-ray, neutron scattering, and theoretical calculations identify open C-B-N and N-B-N defect motifs as the primary active sites. This work establishes a generalizable strategy to engineer crystalline, porous, defect-rich two-dimensional lattices and demonstrates a highly active metal-free platform for LOHC dehydrogenation with high-purity H2 generation.