pro bono       
adjective, adverb uk/ˌprəʊ ˈbəʊ.nəʊ/ us/ˌproʊ ˈboʊ.noʊ/
 (指已经做了的工作,尤指律师的工作)未要求收费的
(relating to work that is done, especially by a lawyer) without asking for payment
  pro bono cases/lawyers/work 未要求收费的案子/律师/工作 
 He takes on some charity cases pro bono. 他接收一些慈善机构的案子,不要求收费。