diff --git a/src/comproscanner/comproscanner.py b/src/comproscanner/comproscanner.py
index d780e1ed..a2a85c7c 100644
--- a/src/comproscanner/comproscanner.py
+++ b/src/comproscanner/comproscanner.py
@@ -54,11 +54,13 @@
 
 class ComProScanner:
     def __init__(self, main_property_keyword: str = None):
-        self.main_property_keyword = main_property_keyword
-        if self.main_property_keyword is None:
-            raise ValueErrorHandler(
-                "Please provide a main property keyword to proceed."
-            )
+    if main_property_keyword is None:
+        raise ValueErrorHandler(
+            "Please provide a main property keyword to proceed."
+        )
+
+    self.main_property_keyword = main_property_keyword.replace(" ", "_")
+    self.main_property_search_keyword = self.main_property_keyword.replace("_", " ")
 
     def collect_metadata(
         self,
@@ -501,7 +503,7 @@ def extract_composition_property_data(
                 f"results/extracted_data/{self.main_property_keyword}/related_figures"
             )
         if materials_data_identifier_query is None:
-            materials_data_identifier_query = f"Is there any material chemical composition and corresponding {self.main_property_keyword} value mentioned in the paper? Give one word answer. Either yes or no."
+            materials_data_identifier_query = f"Is there any material chemical composition and corresponding {self.main_property_search_keyword} value mentioned in the paper? Give one word answer. Either yes or no."
         preparator = MatPropDataPreparator(
             main_property_keyword=self.main_property_keyword,
             main_extraction_keyword=main_extraction_keyword,
diff --git a/src/comproscanner/metadata_extractor/fetch_metadata.py b/src/comproscanner/metadata_extractor/fetch_metadata.py
index 6ca8f42b..2248ba44 100644
--- a/src/comproscanner/metadata_extractor/fetch_metadata.py
+++ b/src/comproscanner/metadata_extractor/fetch_metadata.py
@@ -115,8 +115,16 @@ def _construct_url(self, cursor, year, query, special_query):
         Returns:
             str: The constructed URL
         """
-        base = f"{self.base_url}PUBYEAR+%3D+{year}+{query}"
-        url = base + (f"+{special_query}" if special_query else "") + "&count=200"
+        search_query = query.replace("_", " ")
+encoded_query = urllib.parse.quote(search_query.replace(" ", " AND "))
+encoded_special_query = (
+    urllib.parse.quote(special_query.replace("_", " ").replace(" ", " AND "))
+    if special_query
+    else ""
+)
+
+        base = f"{self.base_url}PUBYEAR+%3D+{year}+{encoded_query}"
+        url = base + (f"+{encoded_special_query}" if encoded_special_query else "") + "&count=200"
         url += f"&cursor={cursor}"
         return url