{'fraction_non_alphanumeric': 0.030876494023904383, 'fraction_numerical': 0.00199203187250996, 'mean_word_length': 5.1656441717791415, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Biphenylene Sheet: A Nonbenzenoid Carbon Allotrope

The quest for planar sp2-hybridized carbon allotropes other than 
graphene, such as graphenylene and biphenylene sheet, has stimulated 
substantial research efforts because of the materials' predicted unique 
mechanical, electronic and transport properties. However, their 
synthesis remains challenging due to the lack of reliable protocols for 
generating non-hexagonal rings during the in-plane tiling of carbon 
atoms. Here, we report the bottom-up growth of ultra-flat biphenylene 
sheet with periodically arranged four-, six-, and eight-membered rings 
of sp2 carbon atoms, via an unprecedented on-surface inter-polymer 
hydrogen fluoride (HF)-zipping reaction. The characterization of this 
biphenylene sheet by scanning probe methods solves the long-standing 
controversy over its dielectric or metallic nature. We expect the 
inter-polymer HF-zipping method to complement the toolbox for the 
synthesis of other nonbenzenoid carbon allotropes.