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A highly flexible and highly sensitive piezoresistive sensor was fabricated by using MXenes and polyvinyl butyral.

Two-dimensional (2D) covalent organic frameworks (COFs) have received much attention due to their tunable electronic structures and superior surface area in visible-light-driven water splitting. Compared to traditional photocatalysts, 2D COFs...

Porous carbon as an electrode material has attracted extensive attention in the field of energy storage. Herein, to promote the energy density of carbon‐based materials, a class of in situ nitrogen‐doped 3D carbon skeleton with hierarchical pores through the structural evolution of pyridine‐incorporated porous covalent triazine‐based framework (p‐CTFs) is rationally designed and prepared. The controlled microscopic pore structure and nitrogen doping concentration can be achieved by varying the polymerization temperature. The experimental results show that p‐CTF‐800 has a large specific surface area (2795 m2 g−1), a rich nitrogen content (11.82%), and a broad pore size distribution (0.65–5 nm), and exhibited an excellent specific capacitance of 406 F g−1 in three‐electrode system and 245.7 F g−1 in water‐based symmetric supercapacitor. When using ionic liquid 1‐ethyl‐3‐methylimidazolium tetraflfluoroborate as electrolyte, the energy density can reach 77 Wh kg−1 at a power density of 175 W kg−1, and still remain at 56.4 Wh kg−1 even at a power density up to 8749 W kg−1. Moreover, p‐CTF‐800‐supercapacitor presents excellent cyclic stability (94% energy retention after 20 000 cycles for IL electrolytes) under current density of 4 A g−1. These results indicate that as‐prepared p‐CTFs can behave as excellent electrode candidate materials for the future high‐performance energy storage devices.

Carbon dots (CDs) with long-lived room-temperature phosphorescence (RTP) or long afterglow properties draw much attention. However, most room-temperature phosphorescent materials are metal containing, and the exploitation of long-lived color-tunable RTP materials faces great challenges. Here, we report metal-free borondoped CDs (B-CDs) for room-temperature phosphorescence with tunable color and an ultralong lifetime. B-CDs were obtained by simply calcining a mixture of boric acid and 1,3,5-benzenetricarboxylic acid in the atmosphere. The as-prepared B-CDs were characterized through UV−vis spectroscopy, photoluminescence spectroscopy, and so forth. Under the excitation of 310 nm UV light, B-CDs show RTP that appears as blue with a phosphorescence lifetime of 1042 ms, and after switching the excited wavelength to 365 nm, the RTP appears as green with a phosphorescence lifetime of 590 ms. Due to the unique RTP properties, B-CDs display promising applications in anticounterfeiting and information encryption.